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  • 1
    Electronic Resource
    Electronic Resource
    The role of manganese in photosynthetic water oxidation (1991)
    Springer
    BioMetals 4 (1991), S. 73-80 
    Details
    ISSN: 1572-8773
    Keywords: Photosynthesis ; Photosystem II ; Water oxidation ; Plastoquinone ; Manganese
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The process of photosynthetic water oxidation to dioxygen under proton release takes place via a sequence of four univalent redox steps in a manganese-containing unit. In this mini-review the current state of knowledge is briefly described with special emphasis on the following topics: (a) the nature of the catalytic site, (b) the structure of the redox chemistry of the manganese-containing active site, (c) the ligand structure and the entry of substrate water into the redox cycle, and (d) problems of the stoichiometry of proton release coupled with individual redox steps and the possible role of other cofactors (Cl−, Ca2+).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01135382
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  • 2
    Electronic Resource
    Electronic Resource
    Light energy conversion with pheophytina monolayer at the SnO2 optically transparent electrode (1994)
    Springer
    Journal of solution chemistry 23 (1994), S. 223-248 
    Details
    ISSN: 1572-8927
    Keywords: Photosynthesis ; pheophytina ; photoelectrochemistry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The photoelectrochemical, absorption and fluorescence properties of pheophytin a mono- and multilayers, deposited on optically transparent tin oxide electrodes and quartz slides were investigated. Spectra of photocurrents coincided with the absorption spectra of photosynthetic pigment in monolayers at the SnO2/solution interfaces. The anodic and cathodic photocurrents were measured at various electrode potentials. Effects of pH, electrode potentials, and concentration of redox reagents on the conversion of solar energy in monolayers on optically transparent electrodes are discussed. The absorption and fluorescence spectral characteristics, and fluorescence lifetime measurements of pheophytina in monolayers and thin films are also discussed in view of the aggregation properties of the photosynthetic pigment. The thermodynamics of adsorption of large amphiphilic compounds at the interface between two immiscible liquids is considered. The adsorption behavior of pheophytin a dissolved in different solvents is investigated. The thermodynamic parameters of pheophytin a adsorption at octane/water and benzene/water interfaces were determined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00973548
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  • 3
    Electronic Resource
    Electronic Resource
    Quantum efficiency requirements for an anaerobic photobioreactor (1990)
    Springer
    Journal of industrial microbiology and biotechnology 5 (1990), S. 337-354 
    Details
    ISSN: 1476-5535
    Keywords: Chlorobium ; Photosynthesis ; Quantum efficiency ; Photobioreactor ; Light intensity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The effect of light intensity, surface area of illuminated bioreactor, H2S flow rate and various wavelength regions of light on oxidative sulfur metabolism byChlorobium was examined. The regulation of oxidative sulfur metabolism by light intensity led to the determination of the photobioreaction quantum efficiency (PQE) for this system. This efficiency is defined as the molecules of sulfur (So) produced per photon utilized and can be used in designing a light efficient photobioreactor. Included in our analysis of requirements for a light efficient photobioreactor is a summary of some fed-batch equations which can be used to model a productive path for the formation of sulfur duringChlorobium's photosynthesis. It is suggested that the incorporation of PQE and fed-batch formulae into expressions for wavelength dependent rates of photosynthetic product formation will lead to a more accurate mathematical model for anoxygenic as well as oxygenic photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01578093
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  • 4
    Electronic Resource
    Electronic Resource
    Leaf gas exchange characteristics, daily carbon and water balances of the host/mistletoe pair Eucalyptus behriana F. Muell. and Amyema miquelii (Lehm. ex Miq.) Tiegh. at permanently low plant water status in the field (1992)
    Springer
    Trees 7 (1992), S. 1-7 
    Details
    ISSN: 1432-2285
    Keywords: Amyema miquelii ; Daily carbon balance ; Daily water balance ; Eucalyptus behriana ; Photosynthesis ; Water-use efficiency ; Xylem pressure ; Heterotrophy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Leaf gas exchange and xylem pressures of the xylem-tapping mistletoe, Amyema miquelii (Lehm. ex Miq.) Tiegh., and its host, Eucalyptus behriana F. Muell., both growing under permanently low plant water status, are studied under controlled and naturally fluctuating field conditions. Stomata of both plants regulate transpiration with respect to light and air humidity, but leaf conductances and total daily transpiration are up to 7.3 times higher in the host. Despite this, water-use efficiency in the mistletoe is lower than in the host. In the light of the mistletoe's low transpiration rates observed in spring, a commonly accepted pattern of higher water losses from parasites is likely to be inconsistent over a season. The role of partial parasitic carbon heterotrophy is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225225
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  • 5
    Electronic Resource
    Electronic Resource
    The effects of water and multi-nutrient stress on xylem sap chemistry, photosynthesis and transpiration of seedlings of two Eucalypts (1992)
    Springer
    Trees 6 (1992), S. 7-12 
    Details
    ISSN: 1432-2285
    Keywords: Eucalyptus ; Nutrients ; Photosynthesis ; Transpiration ; Xylem sap
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Ten seedlings each of Eucalyptus kitsoniana Maiden and Eucalyptus globulus Labill. were subjected to two levels of water stress and two levels of nutrient stress (macro and micro-nutrients) in a greenhouse for 3 weeks. The objectives were to determine the degree to which seedlings show differences in sap chemistry, photosynthesis and transpiration that relate to the environments in which these two species live. Whole plants were then extracted for xylem sap using a pressure chamber and the sap was analyzed for 14 elements using an inductively coupled plasma spectrometer and a nitrometer. For E. kitsoniana water and nutrient stress, applied separately or in combination, significantly reduced leaf conductance, transpiration, photosynthesis and midday water potential. Nutrient stress alone had less effect than water stress on most functions measured. Water stress alone reduced the root/shoot ratio; the combination of water and nutrient stress increased the root/shoot ratio, primarily because of reduced shoot weight. In E. kitsoniana, water stress alone or in combination with nutrient stress increased the xylem sap concentrations of B and Si. Multi-nutrient stress alone, or in combination with water stress, significantly decreased sap Zn and K. For this species, sap N was decreased by nutrient stress, but increased by water stress. E. globulus had significantly lower transpiration rates and less root mass than E. kitsoniana. Slightly lower leaf conductance and photosynthesis were not significant in E. globulus compared to E. kitsoniana. Water and nutrient stress reduced conductance, transpiration (except for nutrient stress) and photosynthesis, and the effects of water stress on E. globulus were greater than the effects of nutrient stress. Midday water potential was reduced by water stress. Water or nutrient stress alone did not alter seedling root/shoot ratio, but the combination of water and nutrient stress significantly increased the root/shoot ratio for both species. For E. globulus, sap concentrations of Mn, Na, Si and K were increased by water stress (alone or in combination with nutrient stress). Sap N increased with water stress or combined stresses, but decreased under nutrient stress alone. When the two species were compared, E. globulus generally had lower or similar nutrient concentrations in the sap, with Ca, Mg, Mn and P significantly lower than in E. kitsoniana. Seedlings of these two species show strong site adaptations to water and nutrient availability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224492
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  • 6
    Electronic Resource
    Electronic Resource
    The influence of ozone on the stomatal and non-stomatal limitation of photosynthesis in Norway spruce, Picea abies (L.) Karst, exposed to soil moisture deficit (1992)
    Springer
    Trees 6 (1992), S. 128-136 
    Details
    ISSN: 1432-2285
    Keywords: Norway spruce ; Ozone ; Photosynthesis ; Stomatal limitation of photosynthesis ; Drought stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Norway spruce, Picea abies (L.) Karst., was exposed to charcoal-filtered air (CF) and non-filtered air + ozone (NF+) and periods of soil moisture deficit from 1985 to 1988 in open-top chambers. Net photosynthesis, stomatal conductance, needle water potential and various shoot properties were measured on 1-year-old shoots during a period of soil moisture deficit. The gas exchange was measured at saturating photosynthetic photon flux density and across a range of CO2 concentrations. The soil moisture deficit induced a mild drought stress in the plants, expressed by a pre-dawn needle water potential of approximately-0.9 MPa and a substantial reduction in net photosynthesis and gas phase conductance. In the CF treatment, intercellular CO2 concentration was reduced, but was unaffected in the NF+ treatment. Furthermore, net photosynthesis declined more in response to the soil moisture deficit in the NF+ treatment than in the CF treatment. This is suggested to be attributed to the carboxylation efficiency at the operating point, which was decreased by 47% and 64% in shoots from the CF and the NF+ treatments, respectively. Stomatal limitation of net photosynthesis was increased by drought by 24–45% in the CF treatment, while it was unaffected in the NF+ treatment. Thus, our results imply that the coupling between the stomatal conductance and the photosynthetic rate was changed and that the marginal cost of water per given amount of carbon gain will increase in trees exposed to ozone, during periods of drought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202428
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  • 7
    Electronic Resource
    Electronic Resource
    Use of simultaneous analysis of gas-exchange and chlorophyll fluorescence quenching for analysing the effects of water stress on photosynthesis in apple leaves (1990)
    Springer
    Trees 4 (1990), S. 1-8 
    Details
    ISSN: 1432-2285
    Keywords: Chlorophyll fluorescence quenching ; Malus ; Photosynthesis ; Water stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary A convenient system for the rapid simultaneous measurement of both chlorophyll fluorescence quenching using a modulated light system, and of CO2, and water vapour exchange by leaves is described. The system was used in a study of the effects of water deficits on the photosynthesis by apple leaves (Malus x domestica Borkh.). Apple leaves were found to have low values of steady-state variable fluorescence, and the existence of significant fluorescence with open traps (Fo) quenching necessitated the measurement and use of a corrected Fo in the calculation of quenching components. Long-term water stress had a marked effect on both gas-exchange and chlorophyll fluorescence quenching. Non-photochemical quenching (qn) in particular was increased in water-stressed leaves, and it was particularly sensitive to incident radiation in such leaves. In contrast, rapid dehydration only affected gas exchange. Relaxation of qn quenching in the dark was slow, taking approximately 10 min for a 50% recovery, in well-watered and in draughted plants, and whether or not the plants had been exposed to high light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00226233
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  • 8
    Electronic Resource
    Electronic Resource
    The influence of leaf area on the rooting physiology of leafy stem cuttings of Terminalia spinosa Engl. (1992)
    Springer
    Trees 6 (1992), S. 210-215 
    Details
    ISSN: 1432-2285
    Keywords: Vegetative propagation ; Percentage rooting ; Leaf area ; Photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effect of different leaf areas on the rooting of Terminalia spinosa Engl. cuttings in an non-mist propagation system in glasshouses at Edinburgh was investigated by trimming the leaves to 0, 7.5, 15 and 30 cm2 before cuttings were severed from stockplants. Cuttings were taken to a standard length of 5 cm from the lateral shoots of previously pruned stockplants grown in a tropicalised glasshouse. During the rooting period, photosynthetic rate, stomatal conductance, water potential and relative water content of the cuttings were assessed at regular intervals. It was found that (i) removal of the entire leaf area prevented rooting; (ii) cuttings with a 7.5 cm2, 15 cm2 and 30 cm2 leaf all achieved 80% rooting after 3 weeks; (iii) an increase in leaf area from 7.5 cm2 to 30 cm2 increased the rate of rooting and the length of the longest root after 2 weeks, but also increased the number of original leaves abscised after 6 weeks; and (iv) the greatest number of new leaves were produced by cuttings with 7.5 cm2 and 15 cm2 leaf area per cutting. All leafy cuttings actively photosynthesized during the propagation period, with a mean rate of 2 μmol CO2 m-2 s-1 with an irradiance of 100 μmol m-2 s-1. Cuttings with 30 cm2 leaf area had lower relative water contents, lower stomatal conductances and lower photosynthetic rates per unit leaf area than those with a 7.5 cm2 and 15 cm2 leaf. It was concluded that T. spinosa cuttings are easy to root, provided the cuttings have leaves to produce current assimilates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224338
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of fruiting on carbon budgets of apple tree canopies (1993)
    Springer
    Trees 8 (1993), S. 56-60 
    Details
    ISSN: 1432-2285
    Keywords: Malus domestica ; Bioenergetics ; Fruit ; Photosynthesis ; Respiration ; Source-sink
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Carbon budgets were calculated from net photosynthesis and dark respiration measurements for canopies of field-grown, 3-year-old apple trees (Malus domestica Borkh.) with maximum leaf areas of 5.4 m2 in a temperature-controlled Perspex tree chamber, measured in situ over 2 years (July 1988 to October 1990) by computerized infrared gas analysis using a dedicated interface and software. Net photosynthesis (Pn) and carbon assimilation per leaf area peaked at respectively 8.3 and 7.7 μmol CO2 m−2 s−1 in April. Net photosynthesis (Pn) and dark respiration (Rd) per tree peaked at 3.6 g CO2 tree−1 h−1 (Pn) and 1.2 g CO2 tree−1 h−1 (Rd), equivalent to 4.2 μmol CO2 (Pn) and 1.4 μmol CO2 (Rd) m−2 s−1 with maximum carbon gain per tree in August and maximum dark respiration per tree in October 1988 and 1989. In May 1990, a tree was deblossomed. Pn (per tree) of the fruiting apple tree canopy exceeded that of the non-fruiting tree by 2–2.5 fold from June to August 1990, attributed to reduced photorespiration (RI), and resulting in a 2-fold carbon gain of the fruiting over the non-fruiting tree. Dark respiration of the fruiting tree canopy progressively exceeded, with increasing sink strength of the fruit, by 51% (June–August), 1.4-fold (September) and 2-fold (October) that of the non-fruiting tree due to leaf (i. e. not fruit) respiration to provide energy (a) to produce and maintain the fruit on the tree and (b) thereafter to facilitate the later carbohydrate translocation into the woody perennial parts of the tree. The fruiting tree reached its optium carbon budget 2–4 weeks earlier (August) then the non-fruiting tree (September 1990). In the winter, the trunk respired 2–100 g CO2 month−1 tree−1. These data represent the first long-term examination of the effect of fruiting without fruit removal which shows increased dark respiration and with the increase progressing as the fruit developed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240982
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  • 10
    Electronic Resource
    Electronic Resource
    Aquatic primary production in relation to microalgal responses to changing light: A review (1991)
    Springer
    Aquatic sciences 53 (1991), S. 187-217 
    Details
    ISSN: 1420-9055
    Keywords: Photosynthesis ; timescales ; respiration ; primary production ; changing light ; phytoplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Dynamic aspects of algal photosynthesis are set against the background of physical water motions which change the light experienced by the phytoplankton. These time-dependent photosynthetic responses are reviewed in relation to the proposition that phytoplankton primary production may be incorrectly estimated by the commonly used “static” incubation of light and dark bottles for periods significantly longer than the response-time of phytoplankton to changing light. This proposition is supported by the clear overlap between the timescales which characterize water motions and the timescales reported for the complex responses of algae to changing light. Empirical studies comparing static and dynamic incubations have been inconclusive, as have models incorporating some representation of the dynamic photosynthetic response to changing light. These results reflect weaknesses in the simple formulations used to describe photosynthesis in relation to irradiance, the simplicity of physical schemes used to generate changes in irradiance with time, and a lack of data (field and laboratory) on dynamic responses of microalgae to changing light. The quantitative significance of many physiological mechanisms is not known in relation to their effect on photosynthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00877059
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  • 11
    Electronic Resource
    Electronic Resource
    Photosynthetic capacity and nitrogen partitioning among species in the canopy of a herbaceous plant community (1994)
    Springer
    Oecologia 100 (1994), S. 203-212 
    Details
    ISSN: 1432-1939
    Keywords: Canopy structure ; Nitrogen use efficiency Photon absorption ; Photosynthesis ; Species coexistence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Partitioning of nitrogen among species was determined in a stand of a tall herbaceous community. Total amount of nitrogen in the aboveground biomass was 261 mmol N m−2, of which 92% was in three dominant species (Phragmites, Calamagrostis and Carex) and the rest was in the other eight subordinate species. Higher nitrogen concentrations per unit leaf area (n L) with increasing photosynthetically active photon flux density (PPFD) were observed in all species except for three short species. The changes in n L within species were mainly explained by the different nitrogen concentrations per unit leaf mass, while the differences in n L between species were explained by the different SLM (leaf mass per unit leaf area). Photon absorption per unit leaf nitrogen (Φ N ) was determined for each species. If photosynthetic activity was proportional to photon absorption, Φ N should indicate in situ PNUE (photosynthetic nitrogen use efficiency). High Φ N of Calamagrostis (dominant) resulted from high photon absorption per unit leaf area (Φ area ), whereas high Φ N of Scutellaria (subordinate) resulted from low n L although its Φ area was low. Species with cylinder-like “leaves” (Juncus and Equisetum) had low Φ N , which resulted from their high n L. Light-saturated CO2 exchange rates per unit leaf area (CER) and per unit leaf nitrogen (potential PNUE) were determined in seven species. Species with high CER and high n L (Phragmites, Carex and Juncus) had low potential PNUE, while species with low CER and low n L showed high potential PNUE. NUE (ratio of dry mass production to nitrogen uptake) was approximated as a reciprocal of plant nitrogen concentration. In most species, three measures of nitrogen use efficiency (NUE, Φ N and potential PNUE) showed strong conformity. Nitrogen use efficiency was high in Calamagrostis and Scutellaria, intermediate in Phragmites and relatively low in Carex. Nitrogen use efficiency of subordinate species was as high as or even higher than that of dominant species, which suggests that growth is co-limited by light and nitrogen in the subordinate species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00316946
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  • 12
    Electronic Resource
    Electronic Resource
    Role of carbonic anhydrase in photosynthesis and inorganic-carbon assimilation in the red alga Gracilaria tenuistipitata (1992)
    Springer
    Planta 187 (1992), S. 275-281 
    Details
    ISSN: 1432-2048
    Keywords: Carbon assimilation ; Carbonic anhydrase ; Carbon dioxide uptake ; Gracilaria ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanism of inorganic-carbon (Ci) accumulation in the red seaweed Gracilaria tenuistipitata Zhang et Xia has been investigated. Extracellular and intracellular carbonic-anhydrase (CA) activities have been detected. Photosynthetic O2 evolution in thalli and protoplasts of G. tenuistipitata were higher at pH 6.5 than at pH 8.6, where HCO 3 − is the predominant form of Ci. Dextran-bound sulfonamide (DBS), a specific inhibitor of extracellular CA, reduced photosynthetic O2 evolution at pH 8.6 and did not have any effect at pH 6.5. After inhibition with DBS, O2 evolution was similar to the rate that could be supported by CO2 from spontaneous dehydration of HCO 3 − . The rate of photosynthetic alkalization of the surrounding medium by the algal thallus was dependent on the concentration of Ci and inhibited by DBS. We suggest that the general form of Ci that enters through the plasma membrane of G. tenuistipitata is CO2. Bicarbonate is utilized mainly by an indirect mechanism after dehydration to CO2, and this mechanism involves extracellular CA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201951
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  • 13
    Electronic Resource
    Electronic Resource
    Starch synthesis in developing wheat grain (1990)
    Springer
    Planta 181 (1990), S. 104-108 
    Details
    ISSN: 1432-2048
    Keywords: Endosperm ; Grain filling ; Pericarp ; Photosynthesis ; Starch synthesis ; Triticum (starch synthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of light on the in-vivo rate of starch synthesis in the endosperm of developing wheat (Triticum aestivum cv. Mardler) grain was studied. Individual grains from spikelets grown on the same spike either in darkness or bright light showed no difference in their ability to accumulate radioactivity or to convert this to starch over a 14-h period. Similarly, there was no difference in final grain dry weight between spikes which had been kept in either darkness or normal light from 10 d post anthesis. In contrast, when “half-grains” (grain which had been bisected longitudinally along the crease region) were incubated by being submerged in culture solution (in vitro) the incorporation of [14C]sucrose into starch was stimulated by increased irradiance. Further experiments showed that the in-vitro dependence on light could be linked to the availability of oxygen. We suggest that in vitro the diffusion of oxygen into the endosperm cells combined with an increased rate of respiration of the tissue during the incubation causes this limitation. Thus the dependence of starch synthesis on light is an artefact of the in-vitro incubation system. The photosynthetic ability of the green pericarp tissue can be used to prevent the development of anoxia in the endosperm tissue of half-grains incubated in vitro. In conclusion, we propose that starch synthesis in vivo is not dependent on oxygen production by photosynthesis in the green layer of the pericarp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202331
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  • 14
    Electronic Resource
    Electronic Resource
    Role of external carbonic anhydrase in light-dependent alkalization by Fucus serratus L. and Laminaria saccharina (L.) Lamour. (Phaeophyta) (1992)
    Springer
    Planta 188 (1992), S. 1-6 
    Details
    ISSN: 1432-2048
    Keywords: Alkalization ; Carbon assimilation ; Carbonic anhydrase ; Fucus ; Laminaria ; Macroalgae ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has been proposed that many marine macroalgae are able to utilize HCO 3 − for photosynthesis and growth, and that energy-dependent ion pumping is involved in this process. We have therefore studied the light-dependent alkalization of the surrounding medium by two species of marine macroscopic brown algae, Fucus serratus L. and Laminaria saccharina (L.) Lamour. with the aim of investigating the role of extracellular carbonic anhydrase (EC 4.2.1.1.) in the assimilation of inorganic carbon from the seawater medium. In particular, the influence of membrane-impermeable or slowly permeable carbonic-anhydrase inhibitors on the rate of alkalization of the seawater has been investigated. Inhibition of the alkalization rate occurred in both species at an alkaline pH (pH 8.0) but no inhibition was observed at an acidic pH (pH 6.0). The alkalization was found to be light-dependent and inhibited by 3-(3′,4′-dichlorophenyl)-1, 1-dimethylurea and, thus, correlated with photosynthesis. Alkalization by macroalgae has previously been shown to be proportional to inorganiccarbon uptake. We suggest that alkalization of the medium at alkaline pH in both of the species examined is mainly the consequence of an extracellular reaction. The reaction is catalyzed by extracellular carbonic anhydrase which converts HCO 3 − to OH− and CO2; CO2 is then taken up through the plasmalemma. However, we do not exclude the involvement of other mechanisms of inorganic-carbon uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00198932
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  • 15
    Electronic Resource
    Electronic Resource
    Role of external carbonic anhydrase in light-dependent alkalization byFucus serratus L. andLaminaria saccharina (L.) Lamour. (Phaeophyta) (1992)
    Springer
    Planta 188 (1992), S. 1-6 
    Details
    ISSN: 1432-2048
    Keywords: Alkalization ; Carbon assimilation ; Carbonic anhydrase ; Fucus ; Laminaria ; Macroalgae ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has been proposed that many marine macroalgae are able to utilize HCO 3 − for photosynthesis and growth, and that energy-dependent ion pumping is involved in this process. We have therefore studied the light-dependent alkalization of the surrounding medium by two species of marine macroscopic brown algae,Fucus serratus L. andLaminaria saccharina (L.) Lamour. with the aim of investigating the role of extracellular carbonic anhydrase (EC 4.2.1.1.) in the assimilation of inorganic carbon from the seawater medium. In particular, the influence of membrane-impermeable or slowly permeable carbonic-anhydrase inhibitors on the rate of alkalization of the seawater has been investigated. Inhibition of the alkalization rate occurred in both species at an alkaline pH (pH 8.0) but no inhibition was observed at an acidic pH (pH 6.0). The alkalization was found to be light-dependent and inhibited by 3-(3′,4′-dichlorophenyl)-1, 1-dimethylurea and, thus, correlated with photosynthesis. Alkalization by macroalgae has previously been shown to be proportional to inorganiccarbon uptake. We suggest that alkalization of the medium at alkaline pH in both of the species examined is mainly the consequence of an extracellular reaction. The reaction is catalyzed by extracellular carbonic anhydrase which converts HCO 3 − to OH− and CO2; CO2 is then taken up through the plasmalemma. However, we do not exclude the involvement of other mechanisms of inorganic-carbon uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01160705
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  • 16
    Electronic Resource
    Electronic Resource
    “Sink” regulation of photosynthetic metabolism in transgenic tobacco plants expressing yeast invertase in their cell wall involves a decrease of the Calvin-cycle enzymes and an increase of glycolytic enzymes (1991)
    Springer
    Planta 183 (1991), S. 40-50 
    Details
    ISSN: 1432-2048
    Keywords: Cell-wall invertase ; Photosynthesis ; Sink regulation (photosynthetic metabolism) ; Transgenic plant (tobacco)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaves on transgenic tobacco plants expressing yeast-derived invertase in the apoplast develop clearly demarcated green and bleached sectors when they mature. The green areas contain low levels of soluble sugars and starch which are turned over on a daily basis, and have high rates of photosynthesis and low rates of respiration. The pale areas accumulate carbohydrate, photosynthesis is inhibited, and respiration increases. This provides a model system to investigate the “sink” regulation of photosynthetic metabolism by accumulating carbohydrate. The inhibition of photosynthesis is accompanied by a decrease of ribulose-1,5-bisphosphate and glycerate-3-phosphate, and an increase of triosephosphate and fructose-1,6-bisphosphate. The extracted activities of ribulose-1,5-bisphosphate carboxylase, fructose-1, 6-bisphosphatase and NADP-glyeraldehyde-3-phosphate dehydrogenase decreased. The activity of sucrose-phosphate synthase remained high or increased, an increased portion of the photosynthate was partitioned into soluble sugars rather than starch, and the pale areas showed few or no oscillations during transitions between darkness and saturating light in saturating CO2. The increased rate of respiration was accompanied by an increased level of hexose-phosphates, triose-phosphates and fructose-1,6-bisphosphate while glycerate-3-phosphate and phosphoenolpyruvate decreased and pyruvate increased. The activities of pyruvate kinase, phosphofructokinase and pyrophosphate: fructose-6-phosphate phosphotransferase increased two- to four-fold. We conclude that an increased level of carbohydrate leads to a decreased level of Calvin-cycle enzymes and, thence, to an inhibition of photosynthesis. It also leads to an increased level of glycolytic enzymes and, thence, to a stimulation of respiration. These changes of enzymes are more important in middle- or long-term adjustments to high carbohydrate levels in the leaf than fine regulation due to depletion of inorganic phosphate or high levels of phosphorylated metabolites.
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    URL: http://dx.doi.org/10.1007/BF00197565
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  • 17
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    Mass-spectrometric determination of O2 and CO2 gas exchange in illuminated higher-plant cells (1991)
    Springer
    Planta 183 (1991), S. 150-157 
    Details
    ISSN: 1432-2048
    Keywords: Cell culture (photoautotrophic) ; Dianthus (gas exchange) ; Gas exchange ; Photosynthesis ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to estimate photosynthetic and respiratory rates in illuminated photoautotrophic cells of carnation (Dianthus caryophyllus L.), simultaneous measurements of CO2 and O2 gas exchange were performed using 18O2, 13CO2 and a mass-spectrometry technique. This method allowed the determination, and thus the comparison, of unidirectional fluxes of O2 and CO2. In optimum photosynthetic conditions (i.e. in the presence of high light and a saturating level of CO2), the rate of CO2 influx represented 75±5% of the rate of gross O2 evolution. After a dark-to-light transition, the rate of CO2 efflux was inhibited by 50% whereas the O2-uptake rate was little affected. The effect of a recycling of respiratory CO2 through photosynthesis on the exchange of CO2 gas was investigated using a mathematical model. The confliction of the experimental data with the simulated gas-exchange rates strongly supported the view that CO2 recycling was a minor event in these cells and could not be responsible for the observed inhibition of CO2 efflux. On the basis of this assumption it was concluded that illumination of carnation cells resulted in a decrease of substrate decarboxylations, and that CO2 efflux and O2 uptake were not as tightly coupled in the light as in the dark. Furthermore, it could be calculated from the rate of gross photosynthesis that the chloroplastic electron-transport chain produced enough ATP in the light to account for the measured CO2-uptake rate without involving cyclic transfer of electrons around PS I or mitochondrial supplementation.
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    URL: http://dx.doi.org/10.1007/BF00197782
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  • 18
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    Decreased ribulose-1,5-bisphosphate carboxylase-oxygenase in transgenic tobacco transformed with “antisense” rbcS (1993)
    Springer
    Planta 190 (1993), S. 1-9 
    Details
    ISSN: 1432-2048
    Keywords: Biomass allocation ; Nicotiana ; Nitrogen nutrition ; Photosynthesis ; Relative growth rate ; Ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) ; Transgenic plant (tobacco antisense DNA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Wild-type tobacco (Nicotiana tabacum L.) plants and transgenic tobacco transformed with antisense rbcS to decrease expression of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco; EC 4.1.1.39) were grown at 300 mol-m−2 · s−1 irradiance and 20° C at either 0.1, 0.7 or 5 mM NH4NO3. In high nitrogen (N), growth was reduced in parallel with the inhibition of photosynthesis when Rubisco was decreased by genetic manipulation. In limiting N, photosynthesis was reduced strongly when Rubisco was decreased by genetic manipulation, but growth was hardly affected. At all N levels, decreased expression of Rubisco led to a decrease in the amount of starch accumulated in the leaves. There was a large increase of the specific leaf area (SLA; leaf area maintained per unit dry weight in the leaf) in plants with decreased Rubisco. Increased SLA was associated with an increased inorganic and a decreased carbon contribution to leaf structural dry weight. The increased SLA represents a more efficient investment of photosynthate with respect to maximisation of leaf area and light interception, and partly compensates for the decreased rate of photosynthesis in plants with decreased expression of Rubisco. The changes of starch content and SLA were particularly large in limiting N, when growth rate was effectively independent of the rate of photosynthesis. Increased N availability led to a large increase of the shoot/ root ratio, but only a small increase in SLA. It is argued that N availability and the availability of photosynthate both regulate storage and allocation of biomass to optimize resource utilization, but achieve this via different mechanisms.
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    URL: http://dx.doi.org/10.1007/BF00195668
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  • 19
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    Influence of the tobacco mosaic virus 30-kDa movement protein on carbon metabolism and photosynthate partitioning in transgenic tobacco plants (1993)
    Springer
    Planta 190 (1993), S. 88-96 
    Details
    ISSN: 1432-2048
    Keywords: Carbon allocation ; Movement protein ; Nicotiana ; Photosynthesis ; Plasmodesma ; Tobacco mosaic virus ; Transgenic tobacco
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transgenic tobacco (Nicotiana tabacum L.) plants expressing the 30-kDa movement protein of tobacco mosaic virus (TMV-MP) were employed to investigate the influence of a localized change in mesophyll-bundle sheath plasmodesmal size exclusion limit on photosynthetic performance and on carbon metabolism and allocation. Under conditions of saturating irradiance, tobacco plants expressing the TMV-MP were found to have higher photosynthetic CO2-response curves compared with vector control plants. However, this difference was significant only in the presence of elevated CO2 levels. Photosynthetic measurements made in the green-house, under endogenous growth conditions, revealed that there was little difference between TMV-MP-expressing and control tobacco plants. However, analysis of carbon metabolites within source leaves where a TMV-MP-induced increase in plasmodesmal size exclusion limit had recently taken place established that the levels of sucrose, glucose, fructose and starch were considerably elevated above those present in equivalent control leaves. Although expression of the TMV-MP did not alter total plant biomass, it reduced carbon allocation to the lower region of the stem and roots. This difference in biomass distribution was clearly evident in the lower root-to-shoot ratios for the TMV-MP transgenic plants. Microinjection (dye-coupling) studies established that the TMV-MP-associated reduction in photosynthate delivery (allocation) to the roots was not due to a direct effect on root cortical plasmodesmata. Rather, this change appeared to result from an alteration in phloem transport from young source leaves in which the TMV-MP had yet to exert its influence over plasmodesmal size exclusion limits. These results are discussed in terms of the rate-limiting steps involved in sucrose movement into the phloem.
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    URL: http://dx.doi.org/10.1007/BF00195679
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  • 20
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    Light activation and molecular-mass changes of NAD(P)-glyceraldehyde 3-phosphate dehydrogenase of spinach and maize leaves (1993)
    Springer
    Planta 190 (1993), S. 313-319 
    Details
    ISSN: 1432-2048
    Keywords: Calvin cycle ; Glyceraldehyde 3-phosphate dehydrogenase, NAD(P)-dependent ; Photosynthesis ; Spinacia ; Zea
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light modulation of chloroplast glyceraldehyde 3-phosphate dehydrogenase (NAD(P)-GAPDH; EC 1.2.1.13) has been investigated. Complete activation of NADPH-dependent activity is achieved at 25 W.m−2 photosynthetically active radiation in spinach (Spinacia oleracea L.) and 100 W.m−2 in maize (Zea mays L.) leaves. Light activation is stronger in spinach (fivefold on average) than in maize (twofold), which shows higher “dark” activity. The NADH dependent activity does not change appreciably. Several substrate activators can simulate in vitro the light effect with recovery of latent NADPH-dependent activity of spinach enzyme, but they are almost inactive with maize enzyme. A mixture of activators has been devised to fully activate the spinach enzyme under most conditions. The NAD(P)-GAPDH protein can be resolved by rapid gel filtration (fast protein liquid chromatography) into three conformers which have different molecular masses according to the light conditions. Enzyme from darkened leaves or chloroplasts, or dichlorophenyl-1,1-dimethylurea-treated chloroplasts is mainly a 600-kDa regulatory form with low NADPH-dependent activity relative to NADH-activity. Enzyme from spinach leaves or chloroplasts during photosynthesis is mainly a 300-kDa oligomer, which along with the 600-kDa form also occurs in leaves of darkened maize. The conformer of illuminated maize leaves is mainly a 160-kDa species. Results are consistent with a model of NAD(P)-GAPDH freely interconvertible between protomers of the 160-kDa (or 300-kDa intermediate) form with high NADPH-activity, produced in the light by the action of thioredoxin and activating metabolites (spinach only), and a regulatory 600-kDa conformer with lower NADPH-activity produced in darkness or when photosynthesis is inhibited. This behavior is reminiscent of the in-vitro properties of purified enzyme; therefore, it seems unlikely that NAD(P)-GAPDH in the chloroplast is part of a stable multienzyme complex or is bound to membranes.
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    URL: http://dx.doi.org/10.1007/BF00196959
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  • 21
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    Evidence for 18O labeling of photorespiratory CO2 in photoautotrophic cell cultures of higher plants illuminated in the presence of 18O2 (1993)
    Springer
    Planta 190 (1993), S. 407-414 
    Details
    ISSN: 1432-2048
    Keywords: Euphorbia (photorespiration) ; Glycolate pathway ; Oxygen exchange ; Photorespiration ; Photosynthesis ; Post-illumination burst
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The 18O-enrichment of CO2 produced in the light or during the post-illumination burst was measured by mass spectrometry when a photoautotrophic cell suspension of Euphorbia characias L. was placed in photorespiratory conditions in the presence of molecular 18O2. The only 18O-labeled species produced was C18O16O; no C18O18O could be detected. Production of C18O16O ceased after addition of two inhibitors of the photosynthetic carbon-oxidation cycle, aminooxyacetate or aminoacetonitrile, and was inhibited by high levels of CO2. The average enrichment during the post-illumination burst was estimated to be 46 ± 15% of the enrichment of the O2 present during the preceding light period. Addition of exogenous carbonic anhydrase, by catalyzing the exchange between CO2 and H2O, drastically diminished the 18O-enrichment of the produced CO2. The very low carbonio-anhydrase level of the photoautotrophic cell suspension probably explains why the 18O labeling of photorespiratory CO2 could be observed for the first time. These data allow the establishment of a direct link between O2 consumption and CO2 production in the light, and the conclusion that CO2 produced in the light results, at least partially, from the mitochondrial decarboxylation of the glycine pool synthesized through the photosynthetic carbon-oxidation cycle. Analysis of the C18O16O and CO2 kinetics provides a direct and reliable way to assess in vivo the real contribution of photorespiratory metabolism to CO2 production in the light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00196970
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  • 22
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    Evidence for the functioning of photosynthetic CO2-concentrating mechanisms in lichens containing green algal and cyanobacterial photobionts (1993)
    Springer
    Planta 191 (1993), S. 57-70 
    Details
    ISSN: 1432-2048
    Keywords: Carbon dioxide concentrating mechanism ; Carbonic anhydrase ; Cyanobacterium ; Green alga ; Lichens ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic properties of a range of lichens containing both green algal (11 species) and cyanobacterial (6 species) photobionts were examined with the aim of determining if there was clear evidence for the operation of a CO2-concentrating mechanism (CCM) within the photobionts. Using a CO2-gas-exchange system, which allowed resolution of fast transients, evidence was obtained for the existence of an inorganic carbon pool which accumulated in the light and was released in the dark. The pool was large (500–1000 nmol · mg Chl) in cyanobacterial lichens and about tenfold smaller in green algal lichens. In Hypogymnia physodes (L.) Nyl., which contains the green alga Trebouxia jamesii, a small inorganic carbon pool was rapidly formed in the light. Carbon dioxide was released from this pool into the gas phase upon darkening within about 20 s when photosynthesis was inhibited by the carbon-reduction-cycle inhibitor glycolaldehyde. In the absence of this inhibitor, release appeared to be obscured by carboxylation of ribulose bisphosphate. The kinetics of CO2 uptake and release were monophasic. The operation of an active CCM could be distinguished from passive accumulation and release accompanying the reversible light-dependent alkalization of the stroma by the presence of saturation characteristics with respect to external CO2. In Peltigera canina (L.) Willd., which contains the cyanobacterium Nostoc sp., a larger CO2 pool was taken up over a longer period in the light and the release of this pool in the dark was slow, lasting 3–5 min. This pool also accumulated in the presence of glycolaldehyde, and under these conditions the CO2 release was biphasic. In both species, photosynthesis at low CO2 was inhibited by the carbonic-anhydrase inhibitor ethoxyzolamide (EZ). Inhibition could be reversed fully or to a considerable extent by high CO2. In Peltigera, EZ decreased both the accumulation of the CO2 pool by the CCM and the rate of photosynthesis. Free-living cultures of Nostoc sp. showed a similar effect of EZ on photosynthesis, although it was more dramatic than that seen with the lichen thalli. In contrast, in Hypogymnia, EZ actually increased the size of the CO2 pool, although it inhibited photosynthesis. This effect was also seen when glycolaldehyde was present together with EZ. Surprisingly, EZ did not alter the kinetics of either CO2 uptake or release. Taken together, the evidence indicates the operation in cyanobacterial lichens of a CCM which is capable of considerable elevation of internal CO2 and is similar to that reported for free-living cyanobacteria. The CCM of green algal lichens accumulates much less CO2 and is probably less effective than that which operates in cyanobacterial lichens.
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    URL: http://dx.doi.org/10.1007/BF00240896
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  • 23
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    Circadian rhythm and fast responses to blue light of photosynthesis in Ectocarpus (Phaeophyta, Ectocarpales) (1992)
    Springer
    Planta 187 (1992), S. 53-59 
    Details
    ISSN: 1432-2048
    Keywords: Ectocarpus (Phaeophyta) ; Circadian rhythm (photosynthesis) ; Blue light (stimulation of photosynthesis) ; Phase shifting (blue light) ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic oxygen production of Ectocarpus siliculosus (Dillwyn) Lyngb. under continuous high irradiances of red light displayed a circadian rhythm with maxima at about noon. Pulses of blue light induced rapid transient increases in the rate of photosynthesis. The increases started about 15 s after the beginning of blue light and reached their maxima after 3–4 min. This was followed by a gradual decrease. A second peak or shoulder about 20 min later indicated that at least two reactions were involved in the blue-light enhancement of photosynthesis. The magnitude of the response to blue light depended on the phase of the rhythm at which blue light was given. It was high when the red-light photosynthesis was at its troughs, and low at its peaks. Fluence-response curves indicated that the sensitivity to blue light at the peaks of the rhythm was identical to that at the troughs. In addition, blue light shifted the phase of the photosynthetic rhythm, where the essential trigger was the light-off signal. Red light had no specific influence on the circadian rhythm. After darkness, photosynthetic rates were different from those under steady-state conditions. Two different transient bursts in the rate of O2 evolution could be distinguished, an early non-rhythmical one that was probably caused by accumulation of inorganic carbon inside the cells, and a second later one that appeared at the peak activity phases of the ciradian rhythm or after blue light. Its origins are unclear.
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    URL: http://dx.doi.org/10.1007/BF00201623
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    Immunocytochemical localization of phosphoenolpyruvate carboxylase and photosynthetic gas-exchange characteristics in ears of Triticum durum Desf. (1993)
    Springer
    Planta 191 (1993), S. 507-514 
    Details
    ISSN: 1432-2048
    Keywords: Ear bract ; Kernel ; Phosphoenolpyruvate carboxylase (immunolocalization) ; Photosynthesis ; Triticum (photosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The presence and distribution of phosphoenolpyruvate carboxylase (PEPCase) in the glumes and immature grains of durum wheat (Triticum durum Desf.) were studied by electron-microscopical immunolabeling of PEPCase with polyclonal antibodies followed by protein A-gold. Plants were grown under mediterranean field conditions and samples were obtained two weeks after anthesis. In the kernels, high gold label was associated with the unstained areas of the protein bodies of aleurone cells, whereas labeling in the cytoplasm and chloroplasts of the pericarp was slight, although significantly above the background. In the glumes, high gold label was only located in cytoplasmic granules (vesicles) of the mesophyll cells, although labeling in the cytoplasm and chloroplasts was also significantly above the background. These observations in immature kernels and glumes are in accordance with the anaplerotic role of this enzyme, as evidenced in C3 plants. Measurements of apparent photosynthesis and its O2 dependence and CO2 compensation concentration were made on ears and flag leaves of durum wheat. In addition, an analog of phosphoenolpyruvate, 3,3-dichloro-2-dihydroxy-phosphinoylmethyl-2-propenoate, was used to inhibit PEPCase and, thereby, to assess the contribution of the PEPCase to photosynthesis in detached ears. There was no effect of the inhibitor on the apparent photosynthesis of ears. Whereas inhibition of apparent photosynthesis by 210 mL · L−1 O2 in flag leaves was typical of C3 species, inhibition in ears was even greater. The CO2 compensation concentrations in different ear parts were similar to or higher than in flag leaves and the O2 dependence was also comparable (about 70%). Therefore, gas-exchange data give further support to the assumption that a C4 cycle is absent or limited to very low rates in ears of durum wheat.
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    URL: http://dx.doi.org/10.1007/BF00195752
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  • 25
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    Effect of vanadate on photosynthesis and the ATP/ADP ratio in low-CO2-adapted Chlamydomonas reinhardtii cells (1993)
    Springer
    Planta 192 (1993), S. 46-51 
    Details
    ISSN: 1432-2048
    Keywords: ATPase ; Carbon concentrating mechanism ; Carbonic anhydrase ; Chlamydomonas ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have assessed the effect of vanadate as an inhibitor of plasma-membrane ATPase on photosynthesis and the ATP/ADP ratio in Chlamydomonas reinhardtii CW-92 (a mutant strain lacking a cell wall). This effect was compared in low-CO2-adapted cells grown in media bubbled with air containing 400 or 70 μL · L−1 CO2. Evidence is presented indicating that cells grown at 70 μL · L−1 CO2 have a higher rate of photosynthetic O2 evolution than cells grown at 400 μL · L−1 CO2, at limiting carbon concentrations. Extracellular and intracellular carbonic-anhydrase activities were, however, similar in cells grown in both of the low-carbon conditions. Vanadate inhibited, to a different extent, the HCO 3 − -dependent O2 evolution in cells grown at 400 and 70 μL · L−1 CO2. At 400 μM vanadate, inhibition reached 70–75% in cells grown at 400 μL · L−1 but only 50% in those grown at 70 μL · L−1 CO2. The ATP/ADP ratios determined with and without vanadate at limiting concentrations of dissolved inorganic carbon indicated that more ATP was hydrolysed in algae grown at 70 μL · L−1 than in those grown at 400 μL · L−1 CO2. We conclude that the maximal capacity to accumulate dissolved inorganic carbon is inversely related to the CO2 concentration in the medium. Activation and — or synthesis of vanadate-sensitive ATPase may be the major explanation for the higher capacity for HCO 3 − -dependent O2 evolution in cells grown under limited CO2 concentrations.
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    URL: http://dx.doi.org/10.1007/BF00198691
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  • 26
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    Production and diurnal utilization of assimilates in leaves of spinach (Spinacia oleracea L.) and barley (Hordeum vulgare L.) (1994)
    Springer
    Planta 192 (1994), S. 497-501 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid ; Hordeum (leaves) ; Phloem transport ; Photosynthesis ; Spinacia (leaves) ; Sucrose (translocation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Rates of CO2 fixation during the light period and the rates of CO2 release during the night period were measured using mature leaves from 39- to 49-d-old spinach (Spinacia oleracea L., US Hybrid 424; grown in 9 h light, 15 h darkness, daily) and mature leaves from 21-d-old barley (Hordeum vulgare L., cv. Apex; grown in 14 h light, 10 h darkness, daily). At certain times during the light and dark periods leaves were harvested for assay of their contents of soluble carbohydrates, starch, malate and the various amino acids. Evaluation of the results of these measurements shows that in spinach and barley leaves 46% and 26%, respectively, of the carbon assimilated during the light period is deposited in the leaves for export during the night period. Taking into account the carbon consumption in the source leaves by dark respiration, it is evaluated that rates of assimilate export during the light period from spinach and barley leaves [38 and 42 μatom C · (mg Chl)−1 · h−1] are reduced in the dark period to 16 μatom C · (mg Chl)−1 · h−1 in both species. The calculated C/N ratios of the photoassimilates exported during the dark period were 0.029 and 0.015 for spinach and barley leaves, respectively.
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    URL: http://dx.doi.org/10.1007/BF00203587
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  • 27
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    Fructose 2,6-bisphosphate levels in mature leaves of tobacco (Nicotiana tabacum) and potato (Solanum tuberosum) (1994)
    Springer
    Planta 193 (1994), S. 16-20 
    Details
    ISSN: 1432-2048
    Keywords: Fructose 2,6-bisphosphate ; Photosynthesis ; Nicotiana ; Solanum ; Starch ; Sucrose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Here we show that fructose 2,6-bisphosphate cannot be reliably measured in mature leaves of tobacco (Nicotiana tabacum L.), potato (Solanum tuberosum L.), or stinging nettle (Urtica dioica L.) using conventional extraction techniques, since the recoveries of fructose 2,6-bisphosphate added during extraction are poor. However, fructose 2,6-bisphosphate could be extracted by boiling leaves in ethanol and aqueous buffer. Evidence for the reliability of this technique is provided by high recovery measurements of fructose 2,6-bisphosphate added to the leaves before extraction. This extraction method was used to measure changes in the level of fructose 2,6-bisphosphate throughout the photoperiod in tobacco and potato leaves. These changes are compared with the rate of accumulation of sucrose and starch in the leaf samples. Variations in the levels of fructose 2,6-bisphosphate, and the relationship between this metabolite and sucrose and starch accumulation in these leaves during the photoperiod are similar to the pattern observed in leaves of other plant species.
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    URL: http://dx.doi.org/10.1007/BF00191601
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    Relationships among violaxanthin deepoxidation, thylakoid membrane conformation, and nonphotochemical chlorophyll fluorescence quenching in leaves of cotton (Gossypium hirsutum L.) (1994)
    Springer
    Planta 193 (1994), S. 238-246 
    Details
    ISSN: 1432-2048
    Keywords: Chlorophyll fluorescence quenching ; Energy dissipation ; Gossypium ; Light scattering changes ; Photosynthesis ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The kinetics and temperature dependencies of development and relaxation of light-induced absorbance changes caused by deepoxidation of violaxanthin to antheraxanthin and zeaxanthin (ΔZ; peak at 506 nm) and by light scattering (ΔS; peak around 540 nm) as well as of nonphotochemical quenching of chlorophyll fluorescence (NPQ) were followed in cotton leaves. Measurements were made in the absence and the presence of dithiothreitol (DTT), an inhibitor of violaxanthin deepoxidase. The amount of NPQ was calculated from the Stern-Volmer equation. A procedure was developed to correct gross AS (ΔSg) for absorbance changes around 540 nm that are due to a spectral overlap with ΔZ. This protocol isolated the component which is caused by light-scattering changes alone (ΔSn). In control leaves, the kinetics and temperature dependence of the initial rate of rise in ΔSn that takes place upon illumination, closely matched that of ΔZ. Application of DTT to leaves, containing little zeaxanthin or antheraxanthin, strongly inhibited both ΔSn and NPQ, but DTT had no inhibitory effect in leaves in which these xanthophylls had already been preformed, showing that the effect of DTT on ΔAn and NPQ results solely from the inhibition of violaxanthin deepoxidation. The rates and maximum extents of ΔSn and NPQ therefore depend on the amount of zeaxanthin (and/or antheraxanthin) present in the leaf. In contrast to the situation during induction, relaxation of ΔZ upon darkening was much slower than the relaxation of ΔSn and NPQ. The relaxation of ΔSn and NPQ showed quantitatively similar kinetics and temperature dependencies (Q10=2.4). These results are consistent with the following hypotheses: The increase in lumen-proton concentration resulting from thylakoid membrane energization causes deepoxidation of violaxanthin to antheraxanthin and zeaxanthin. The presence of these xanthophylls is not sufficient to cause ΔSn or NPQ but, together with an increased lumen-proton concentration, these xanthophylls cause a conformational change, reflected by ΔSn. The conformational change facilititates nonradiative energy dissipation, thereby causing NPQ. Membrane energization is prerequisite to conformational changes in the thylakoid membrane and resultant nonradiative energy dissipation but the capacity for such changes in intact leaves is quite limited unless zeaxanthin (and/or antheraxanthin) is present in the membrane. The sustained ΔSn and NPQ levels that remain after darkening may be attributable to a sustained high lumen-proton concentration.
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    URL: http://dx.doi.org/10.1007/BF00192536
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  • 29
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    Effect of antisense repression of the chloroplast triose-phosphate translocator on photosynthetic metabolism in transgenic potato plants (1994)
    Springer
    Planta 193 (1994), S. 174-180 
    Details
    ISSN: 1432-2048
    Keywords: Antisense repression ; Photosynthesis ; Solanum ; Starch synthesis ; Triose phosphate translocator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The introduction of an antisense DNA into transgenic potato (Solanum tuberosum L.) plants decreased the expression of the chloroplast triose-phosphate translocator and lowered its activity by 20–30%. With plants propagated from tubers, the effect of the transformation on photosynthetic metabolism was analysed by measuring photosynthesis, the formation of leaf starch, and the total and subcellular metabolite contents in leaves. Although the transformants, in contrast to those propagated from cell cultures, did not differ from the wild-type plants in respect to rates of photosynthesis, plant appearance, growth and tuber production, their photosynthetic metabolism was found to be severely affected. The results show that the decrease in activity of the triose-phosphate translocator in the transformants caused a fourfold increase in the level of 3-phosphoglycerate and a corresponding decrease in inorganic phosphate in the stromal compartment, resulting in a large increase in the synthesis of starch. Whereas during a 12-h day period wild-type plants deposited 43% of their CO2 assimilate into starch, this value rose to 61–89% in the transformants. In contrast to the wild-type plants, where the rate of assimilate export from the leaves during the night period was about 75% of that during the day, the export rate from leaves of transformants appeared to be much higher during the night than during the day. As the mobilisation of starch occurs in part hydrolytically, resulting in the formation of glucose, the triose-phosphate translocator loses its exclusive function in the export of carbohydrates from the chloroplasts when the photoassimilates are temporarily deposited as starch. It appears that by directing the CO2 assimilates mainly into starch, the transformants compensate for the deficiency in triose-phosphate translocator activity in such a way that the productivity of the plants is not affected by the transformation.
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    URL: http://dx.doi.org/10.1007/BF00192527
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    Mechanism of photosystem-I photoinhibition in leaves of Cucumis sativus L. (1994)
    Springer
    Planta 194 (1994), S. 287-293 
    Details
    ISSN: 1432-2048
    Keywords: Chilling stress ; Cucumis (photoinhibition) ; Photoinhibition ; Photosynthesis ; Photosystem I ; Subunit protein degradation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was recently shown that the site of photoinhibition in leaves of Cucumis sativus L. at low temperatures is Photosystem I (PSI), not PSII (I. Terashima et al. 1994, Planta 193, 300–306). In the present study, the mechanisms of this PSI photoinhibition in vivo were examined. By lowering the photon flux density during the photoinhibitory treatment of leaves at 4°C for 5 h to less than 100 μmol·m−2s−1, we were able to separate the steps of the destruction of the electron-transfer components. Although P-700, the reaction-center chlorophyll, was almost intact in this low-light treatment, the quantum yield of the electron transfer through PSI and photochemically induced absorption change at 701 nm were markedly inhibited. This, along with the results from the measurements of the light-induced absorption changes in the presence of various concentrations of methyl viologen, an artificial electron acceptor, indicates that the component on the acceptor side of the PSI, A1 or Fx, is the first site of inactivation. When the photon flux density during the treatment was increased to 220 μmol·m−2s−1, the destruction of P-700 itself was also observed. Furthermore, the partial degradation of the chlorophyll-binding large subunits was observed in photoinhibited leaves. This degradation of the subunits was not detected when the treatment was carried out under nitrogen atmosphere, the condition in which the electron transfer is not inhibited. Thus, the photoinhibitory processes in the reaction center of PSI go through three steps, the inactivation of the acceptor side, the destruction of the reaction-center chlorophyll and the degradation of the reaction center subunit(s). The similarities and the differences between the mechanisms of PSI photoinhibition and those of PSII photoinhibition are discussed.
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    URL: http://dx.doi.org/10.1007/BF00196400
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    Mechanistic differences in photoinhibition of sun and shade plants (1992)
    Springer
    Planta 188 (1992), S. 422-431 
    Details
    ISSN: 1432-2048
    Keywords: Light acclimation ; Photosynthesis ; Photoinhibition ; Photosystem II repair cycle ; Pisum ; Tradescantia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Leaf discs of the shade plant Tradescantia albiflora Kunth grown at 50 μmol · m−2 · s−1, and the facultative sun/shade plant Pisum sativum L. grown at 50 or 300 μmol · m−2, s−1, were photoinhibited for 4 h in 1700 μmol photons m−2 · s−1 at 22° C. The effects of photoinhibition on the following parameters were studied: i) photosystem II (PSII) function; ii) amount of D1 protein in the PSII reaction centre; iii) dependence of photoinhibition and its recovery on chloroplast-encoded protein synthesis; and, iv) the sensitivity of photosynthesis to photoinhibition in the presence or absence of the carotenoid zeaxanthin. We show that: i) despite different sensitivities to photoinhibition, photoinhibition in all three plants occurred at the reaction centre of PSII; ii) there was no correlation between the extent of photoinhibition and the degradation of the D1 protein; iii) the susceptibility to photoinhibition by blockage of chloroplas-tencoded protein synthesis was much less in shade plants than in plants acclimated to higher light; and iv) inhibition of zeaxanthin formation increased the sensitivity to photoinhibition in pea, but not in the shade plant Tradescantia. We suggest that there are mechanistic differences in photoinhibition of sun and shade plants. In sun plants, an active repair cycle of PSII replaces photoinhibited reaction centres with photochemically active ones, thereby conferring partial protection against photoinhibition. However, in shade plants, this repair cycle is less important for protection against photoinhibition; instead, photoinhibited PSII reaction centres may confer, as they accumulate, increased protection of the remaining connected, functional PSII centres by controlled, nonphotochemical dissipation of excess excitation energy.
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    URL: http://dx.doi.org/10.1007/BF00192810
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    Environmental effects on circadian rhythms in photosynthesis and stomatal opening (1993)
    Springer
    Planta 189 (1993), S. 369-376 
    Details
    ISSN: 1432-2048
    Keywords: Circadian rhythm ; Phaseolus ; Photosynthesis ; Stomate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Persistent circadian rhythms in photosynthesis and stomatal opening occurred in bean (Phaseolus vulgaris L.) plants transferred from a natural photoperiod to a variety of constant conditions. Photosynthesis, measured as carbon assimilation, and stomatal opening, as conductance to water vapor, oscillated with a freerunning period close to 24 h under constant moderate light, as well as under light-limiting and CO2-limiting conditions. The rhythms damped under constant conditions conducive to high photosynthetic rates, as did rates of carbon assimilation and stomatal conductance, and this damping correlated with the accumulation of carbohydrate. No rhythm in respiration occurred in plants transferred to constant darkness, and the rhythm in stomatal opening damped rapidly in constant darkness. Damping of rhythms also occurred in leaflets exposed to constant light and CO2-free air, demonstrating that active photosynthesis and not simply light was necessary for sustained expression of these rhythms.
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    URL: http://dx.doi.org/10.1007/BF00194433
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    Decreased ribulose-1,5-bisphosphate carboxylase-oxygenase in transgenic tobacco transformed with “antisense” rbcS (1991)
    Springer
    Planta 183 (1991), S. 542-554 
    Details
    ISSN: 1432-2048
    Keywords: Nicotiana (transformed with antisense DNA) ; Photosynthesis ; Ribulose-1,5-bisphosphate carboxylase-oxygenase ; Transgenic plant (antisense)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Experiments were carried out to determine how decreased expression of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) affects photosynthetic metabolism in ambient growth conditions. In a series of tobacco (Nicotiana tabacum L.) plants containing progressively smaller amounts of Rubisco the rate of photosynthesis was measured under conditions similar to those in which the plants had been grown (310 μmol photons · m−2 · s−1, 350 μbar CO2, 22° C). (i) There was only a marginal inhibition (6%) of photosynthesis when Rubisco was decreased to about 60% of the amount in the wildtype. The reduced amount of Rubisco was compensated for by an increase in Rubisco activation (rising from 60 to 100%), with minor contributions from an increase of its substrates (ribulose-1,5-bisphosphate and the internal CO2 concentration) and a decrease of its product (glycerate-3-phosphate). (ii) The decreased amount of Rubisco was accompanied by an increased ATP/ADP ratio that may be causally linked to the increased activation of Rubisco. An increase of highenergy-state chlorophyll fluorescence shows that thylakoid membrane energisation and high-energy-state-dependent energy dissipation at photosystem two had also increased. (iii) A further decrease of Rubisco (in the range of 50–20% of the wildtype level) resulted in a strong and proportional inhibition of CO2 assimilation. This was accompanied by a decrease of fructose-1,6-bisphosphatase activity, coupling-factor 1 (CF1)-ATP-synthase protein, NADP-malate dehydrogenase protein, and chlorophyll. The chlorophyll a/b ratio did not change, and enolase and sucrose-phosphate synthase activity did not decrease. It is argued that other photosynthetic enzymes are also decreased once Rubisco decreases to the point at which it becomes strongly limiting for photosynthesis. (iv) It is proposed that the amount of Rubisco in the wildtype represents a balance between the demands of light, water and nitrogen utilisation. The wildtype overinvests about 15% more protein in Rubisco than is needed to avoid a strict Rubisco limitation of photosynthesis. However, this “excess” Rubisco allows the wildtype to operate with lower thylakoid energisation, and decreased high-energy-state-dependent energy dissipation, hence increasing light-use efficiency by about 6%. It also allows the wildtype to operate with a lower internal CO2 concentration in the leaf and a lower stomatal conductance at a given rate of photosynthesis, so that instantaneous water-use efficiency is marginally (8%) increased.
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    Regulation of chloroplast metabolism in leaves: Evidence that NADP-dependent glyceraldehydephosphate dehydrogenase, but not ferredoxin-NADP reductase, controls electron flow to phosphoglycerate in the dark-light transition (1991)
    Springer
    Planta 185 (1991), S. 337-343 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast metabolism (metabolism regulation) ; Photosystem I (P700 oxidation) ; Electron transport ; Ferredoxin-NADP reductase ; Glyceraldehydephosphate dehydrogenase ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract P700 is rapidly, but only transiently photooxidized upon illuminating dark-adapted leaves. Initial oxidation is followed by a reductive phase even under far-red illumination which excites predominantly photosystem (PS) I. In this phase, oxidized P700 is reduced by electrons coming from PSII. Charge separation in the reaction center of PSI is prevented by the unavailability of electron acceptors on the reducing side of PSI. It is subsequently made possible by the opening of an electron gate which is situated between PSI and the electron acceptor phosphoglycerate. Electron acceptors immediately available for reduction while the gate is closed corresponded to 10 nmol · (mg chlorophyll)−1 electrons in geranium leaves, 16 nmol · (mg chlorophyll)−1 in sunflower and 22 nmol · (mg chlorophyll)−1 in oleander. Reduction of NADP during the initial phase of P700 oxidation showed that the electron gate was not represented by ferredoxin-NADP reductase. Availability of ATP indicated that electron flow was not hindered by deactivation of the thylakoid ATP synthetase. It is concluded that NADP-dependent glyceraldehydephosphate dehydrogenase is completely deactivated in the dark and activated in the light. The rate of activation depends on the length of the preceding dark period. As chloroplasts contain both NAD- and NADP-dependent glyceraldehydephosphate dehydrogenases, deactivation of the NADP-dependent enzyme disconnects chloroplast NAD and NADP systems and prevents phosphoglycerate reduction in the dark at the expense of NADPH and ATP which are generated by glucose-6-phosphate oxidation and glycolytic starch breakdown, respectively.
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    Activation of spinach chloroplast glyceraldehyde 3-phosphate dehydrogenase: effect of glycerate 1,3-bisphosphate (1993)
    Springer
    Planta 190 (1993), S. 320-326 
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    ISSN: 1432-2048
    Keywords: Calvin cycle ; Glyceraldehyde 3-phosphate dehydrogenase, NAD(P)-dependent ; Glycerate 1,3-bisphosphate ; Photosynthesis ; Spinacia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spinach (Spinacia oleracea L.) chloroplast NAD(P)-dependent glyceraldehyde 3-phosphate dehydrogenase (NAD(P)-GAPDH; EC 1.2.1.13) was purified. The association state of the protein was monitored by fast protein liquid chromatography-Superose 12 gel filtration. Protein chromatographed in the presence of NADP+ and dithiothreitol consisted of highly NADPH-active protomers of 160 kDa; otherwise, it always consisted of a 600-kDa oligomer (regulatory form) favoured by the addition of NAD+ in buffers and with low NADPH-dependent activity (ratio of activities with NADPH versus NADH of 0.2–0.4). Glycerate 1,3-bisphosphate (BPGA) was prepared enzymatically using rabbit-muscle NAD-GAPDH, and purified. Among known modulators of spinach NAD(P)-GAPDH, BPGA is the most effective on a molar basis in stimulating NADPH-activity of “dark” chloroplast extracts and purified NAD(P)-GAPDH (activation constant, K a= 12 μM). It also causes the enzyme to dissociate into 160-kDa protomers. The K m of BPGA both with NADPH or NADH as coenzyme is 4–7 μM. NAD+ and NADH are inhibitory to the activation process induced by BPGA. This compound, together with NADP(H) and ATP belongs to a group of substrate-modifiers of the NADPH-activity and conformational state of spinach NAD(P)-GAPDH, all characterized by K a values three- to tenfold higher than the K m. Since NADP(H) is largely converted to NAD(H) in darkened chloroplasts Heineke et al. 1991, Plant Physiol. 95, 1131–1137, it is proposed that NAD+ promotes NAD(P)-GAPDH association into a regulatory conformer with low NADPH-activity during dark deactivation. The process is reversed in the light by BPGA and other substrate-modifiers whose concentration increases during photosynthesis, in addition to reduced thioredoxin.
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    Decreased ribulose-1,5-bisphosphate carboxylase-oxygenase in transgenic tobacco transformed with “antisense” rbcS (1993)
    Springer
    Planta 190 (1993), S. 332-345 
    Details
    ISSN: 1432-2048
    Keywords: Light climate ; Nicotiana (photosynthesis) ; Photosynthesis ; Ribulose 1,5-bisphosphate carboxylase-oxygenase ; Transgenic plant (tobacco, antisense DNA)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tobacco (Nicotiana tabacum L.) plants transformed with ‘antisense’ rbcS to decrease the expression of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) have been used to investigate the contribution of Rubisco to the control of photosynthesis in plants growing at different irradiances. Tobacco plants were grown in controlled-climate chambers under ambient CO2 at 20°C at 100, 300 and 750 μmol·m−2·s−1 irradiance, and at 28°C at 100, 300 and 1000 μmol·m−2·s−1 irradiance. (i) Measurement of photosynthesis under ambient conditions showed that the flux control coefficient of Rubisco (C infRubisco supA ) was very low (0.01–0.03) at low growth irradiance, and still fairly low (0.24–0.27) at higher irradiance. (ii) Short-term changes in the irradiance used to measure photosynthesis showed that C infRubisco supA increases as incident irradiance rises, (iii) When low-light (100 μmol·m−2·s−1)-grown plants are exposed to high (750–1000 μmol·m−2·s−1) irradiance, Rubisco is almost totally limiting for photosynthesis in wild types. However, when high-light-grown leaves (750–1000 μmol·m−2·s−1) are suddenly exposed to high and saturating irradiance (1500–2000 μmol·m−2·s−1), C infRubisco supA remained relatively low (0.23–0.33), showing that in saturating light Rubisco only exerts partial control over the light-saturated rate of photosynthesis in “sun” leaves; apparently additional factors are co-limiting photosynthetic performance, (iv) Growth of plants at high irradiance led to a small decrease in the percentage of total protein found in the insoluble (thylakoid fraction), and a decrease of chlorophyll, relative to protein or structural leaf dry weight. As a consequence of this change, high-irradiance-grown leaves illuminated at growth irradiance avoided an inbalance between the “light” reactions and Rubisco; this was shown by the low value of C infRubisco supA (see above) and by measurements showing that non-photochemical quenching was low, photochemical quenching high, and NADP-malate dehydrogenase activation was low at the growth irradiance. In contrast, when a leaf adapted to low irradiance was illuminated at a higher irradiance, Rubisco exerted more control, non-photochemical quenching was higher, photochemical quenching was lower, and NADP-malate dehydrogenase activation was higher than in a leaf which had grown at that irradiance. We conclude that changes in leaf composition allow the leaf to avoid a one-sided limitation by Rubisco and, hence, overexcitation and overreduction of the thylakoids in high-irradiance growth conditions, (v) ‘Antisense’ plants with less Rubisco contained a higher content of insoluble (thylakoid) protein and chlorophyll, compared to total protein or structural leaf dry weight. They also showed a higher rate of photosynthesis than the wild type, when measured at an irradiance below that at which the plant had grown. We propose that N-allocation in low light is not optimal in tobacco and that genetic manipulation to decrease Rubisco may, in some circumstances, increase photosynthetic performance in low light.
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    URL: http://dx.doi.org/10.1007/BF00196962
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    Bicarbonate uptake in the marine macroalga Ulva sp. is inhibited by classical probes of anion exchange by red blood cells (1993)
    Springer
    Planta 191 (1993), S. 34-40 
    Details
    ISSN: 1432-2048
    Keywords: Anion exchange(r) (band 3) protein ; Bicarbonate uptake ; Photosynthesis ; Protein (band 3) ; Ulva(photosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We demonstrate in this work that HCO inf3 sup− uptake in the marine macroalga Ulva sp. features functional resemblances to anion transport mediated by anion exchangers of mammalian cell membranes. The evidence is based on (i) competitive inhibition of photosynthesis by the classical red-blood-cell anion-exchange blockers 4,4′-dinitrostilbene-2,2′-disulfonate and 4-nitro-4′-isothiocyanostilbene-2,2′-disulfonate under conditions where HCO inf3 sup− , but not CO2, was the inorganic carbon form taken up; (ii) inhibition of HCO inf3 − uptake by pyridoxal phospate, indicating the involvement of lysine residues in the binding/translocation of HCO inf3 sup− ; and (iii) inhibition of HCO inf3 sup− (but not of CO2) uptake by exofacial trypsin treatments, indicating the functional involvement of a plasmalemma protein. It is suggested that HCO inf3 sup− uptake mediated by such a putative anion transporter can be a fundamental step in providing inorganic carbon for the CO2-concentrating system of marine marcoalgae in an environment where the HCO inf3 sup− concentration is high, but the CO2 concentration and rates of uncatalyzed HCO inf3 sup− dehydration are low.
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    Adenine nucleotides and the xanthophyll cycle in leaves (1994)
    Springer
    Planta 192 (1994), S. 526-536 
    Details
    ISSN: 1432-2048
    Keywords: Adenylate energy charge ; Adenylate kinase equilibrium ; Aegialitis ; Gossypium ; Photosynthesis ; Stress (low temperature, low CO2) ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of varying the steady-state rate of non-cyclic photosynthetic electron transport on the leaf adenylate energy charge and the epoxidation state of the xanthophyll-cycle pigments were determined in leaves of cotton (Gossypium hirsutum L.) and the mangrove (Aegialitis annulata R.Br.). Different photosynthetic rates were obtained by varying the intercellular CO2 concentration and/or the leaf temperature, and in some cases, by changing the leaf conductance to CO2 diffusion. Also determined were the effects of these treatments on the changes in the adenylate energy charge and the epoxidation state of the xanthophyll-cycle pigments that occur after darkening of the leaves. The leaf adenylate pool remained close to equilibrium with the adenylate kinase both in the light at steady state and during dark relaxation. The adenylate energy charge increased as the photosynthetic rate decreased and maximal levels were obtained when CO2 assimilation and, therefore, non-cyclic electron flow were maximally inhibited. This implies that, in nature, photophosphorylation may provide energy needed for ion-pumping and biosynthetic and repair processes, even under stress conditions that severely restrict or prevent photosynthetic gas exchange. High levels of de-epoxidized violaxanthin in the light did not necessarily indicate or depend on a high adenylate energy charge. Dithiothreitol, an inhibitor of the violaxanthin de-epoxidase a nd ascorbate peroxidase, did not inhibit the adenylate energy charge in the light. Thus we conclude that coupled electron transport during inhibited CO2 fixation was not driven by a dithiothreitol-sensitive Mehler ascorbate-peroxidase reaction. The changes in the adenylate energy charge and xanthophyll re-epoxidation that follow when leaves were darkened are strongly affected by the preceding photosynthetic rate. Postillumination fluctuations in adenylate energy charge, both at 15 ° and 27 °C, were most pronounced when the preceding photosynthetic rate was minimal and least pronounced when this rate was maximal. Temperature had a considerably greater influence in the dark on xanthophyll re-epoxidation than on the pattern of adenylate relaxation.
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    A membrane-located polypeptide ofUlva sp. which may be involved in HCO 3 - uptake is recognized by antibodies raised against the human red-blood-cell anion-exchange protein (1994)
    Springer
    Planta 194 (1994), S. 247-249 
    Details
    ISSN: 1432-2048
    Keywords: Anion exchange(r) ; Bicarbonate uptake ; Photosynthesis ; Ulva
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polypeptides present in a membrane fraction of the marine macroalgaUlva sp. were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tested for cross-reactivity with antibodies raised against the human red-blood-cell anion exchanger (AE1). A polypeptide of ca. 95 kDa was identified with a monoclonal, as well as two polyclonal (one against the C-terminus and one against the whole protein) antibodies, indicating that it shares homologous domains with AE1. These findings complement an earlier study which indicated that a plasmalemma-bound, disulfonic stilbenesensitive, protein was functionally involved in HCO 3 - transport into the photosynthesizing cells ofUlva (Z. Drechsler et al. 1993, Planta191, 34–40). It is thus suggested here that a similar protein has evolved, and has been conserved, in marine photosynthetic organisms and mammalian red blood cells for the purpose of HCO 3 - transport.
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    A membrane-located polypeptide of Ulva sp. which may be involved in HCO 3 - uptake is recognized by antibodies raised against the human red-blood-cell anion-exchange protein (1994)
    Springer
    Planta 194 (1994), S. 247-249 
    Details
    ISSN: 1432-2048
    Keywords: Anion exchange(r) ; Bicarbonate uptake ; Photosynthesis ; Ulva
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polypeptides present in a membrane fraction of the marine macroalga Ulva sp. were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and tested for cross-reactivity with antibodies raised against the human red-blood-cell anion exchanger (AE1). A polypeptide of ca. 95 kDa was identified with a monoclonal, as well as two polyclonal (one against the C-terminus and one against the whole protein) antibodies, indicating that it shares homologous domains with AE1. These findings complement an earlier study which indicated that a plasmalemma-bound, disulfonic stilbenesensitive, protein was functionally involved in HCO 3 - transport into the photosynthesizing cells of Ulva (Z. Drechsler et al. 1993, Planta 191, 34–40). It is thus suggested here that a similar protein has evolved, and has been conserved, in marine photosynthetic organisms and mammalian red blood cells for the purpose of HCO 3 - transport.
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    The induction of the CO2-concentrating mechanism is correlated with the formation of the starch sheath around the pyrenoid of Chlamydomonas reinhardtii (1994)
    Springer
    Planta 195 (1994), S. 210-216 
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    ISSN: 1432-2048
    Keywords: Chlamydomonas ; Carbon-dioxide-concentrating mechanism ; Photosynthesis ; Pyrenoid ; Starch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pyrenoid is a prominent proteinaceous structure found in the stroma of the chloroplast in unicellular eukaryotic algae, most multicellular algae, and some hornworts. The pyrenoid contains the enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase and is sometimes surrounded by a carbohydrate sheath. We have observed in the unicellular green alga Chlamydomonas reinhardtii Dangeard that the pyrenoid starch sheath is formed rapidly in response to a decrease in the CO2 concentration in the environment. This formation of the starch sheath occurs coincidentally with the induction of the CO2-concentrating mechanism. Pyrenoid starch-sheath formation is partly inhibited by the presence of acetate in the growth medium under light and low-CO2 conditions. These growth conditions also partly inhibit the induction of the CO2-concentrating mechanism. When cells are grown with acetate in the dark, the CO2-concentrating mechanism is not induced and the pyrenoid starch sheath is not formed even though there is a large accumulation of starch in the chloroplast stroma. These observations indicate that pyrenoid starch-sheath formation correlates with induction of the CO2-concentrating mechanism under low-CO2 conditions. We suggest that this ultrastructural reorganization under lowCO2 conditions plays a role in the CO2-concentrating mechanism C. reinhardtii as well as in other eukaryotic algae.
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    Light-dependent pH changes in leaves of C3 plants (1990)
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    Planta 182 (1990), S. 253-261 
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    ISSN: 1432-2048
    Keywords: Cytosol ; Metabolite ; Photosynthesis ; pH regulation ; Transport ; Vacuoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Illumination of leaves of C3 plants caused cytosolic alkalization and vacuolar acidification in the mesophyll cells. Both phenomena were particularly pronounced when CO2 was absent, were suppressed by CO2, and were related to the activation state of the photosynthetic apparatus. The cytosolic alkalization reaction has at least two major components. Trivalent cytosolic phosphoglycerate must be protonated before it can be transferred into the chloroplasts for reduction. Pumping of protons from the cytosol into the vacuole also contributes to cytosolic alkalization. The dependence of light scattering by chloroplast thylakoids on the energy fluence rate was closely related to that of vacuolar acidification under different conditions for chloroplast energization. This indicates (i) transport of energy from the chloroplasts to the cytosol in the light and (ii) use of this energy for the transport of protons into the vacuoles. The light-dependent vacuolar acidification is interpreted to be caused by the increase in the activity of a proton-translocating enzyme of the tonoplast. The decrease of vacuolar acidification during photosynthetic carbon reduction or photorespiration is indicative of decreased cytosolic energization. In low light, the light-dependent vacuolar acidification was stimulated in the absence of CO2 when photorespiration was inhibited. The data do not support the view that photorespiration is capable of increasing the cytosolic energy state in the light.
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    Light-dependent pH changes in leaves of C3 plants (1990)
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    Planta 182 (1990), S. 244-252 
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    ISSN: 1432-2048
    Keywords: Chloroplast ; Cytosol ; Photosynthesis ; pH ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chloroplasts, mesophyll protoplasts, cytoplasts, vacuoplasts, vacuoles and leaves were stained with pH-indicating fluorescent dyes of differing pK values. Fluorescence microscopy was used to obtain information on the intracellular and intercellular distribution of the probes. The kinetics of blue or green fluorescence emitted from chloroplasts, protoplasts, cytoplasts and leaves was measured during illumination with red light. The intensity of light used for fluorescence excitation was so low that it had little effect on photosynthesis. In leaves, fluorescence signals emitted from chloroplasts were small and usually insignificant compared to signals originating from the cytosol. Both indicated light-dependent alkalization and reversal of alkalization on darkening. Vacuolar signals were opposite in sign to cytosolic signals. They indicated acidification of the vacuole in the light-dark transient and reversal of this effect on darkening.
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    Light-dependent pH changes in leaves of C3 plants (1990)
    Springer
    Planta 182 (1990), S. 262-269 
    Details
    ISSN: 1432-2048
    Keywords: Chloroplast development ; Cytosol ; pH ; Photosynthesis ; Vacuole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Etiolated leaves and the inhibitors of photosynthesis 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) and dl-glyceraldehyde were used to study the relationship between thylakoid energization, photosynthesis, the light-dependent alkalization of the cytosol of mesophyll cells and the acidification of mesophyll vacuoles. No light-dependent pH changes were observed in etiolated leaves. As chloroplasts developed in the light and became photosynthetically competent, mesophyll vacuoles became more acidic when the leaves were illuminated in CO2-free air. Acidification was suppressed and even replaced by a small light-dependent alkaline shift during photoassimilation of CO2. In green leaves, DCMU and dl-glyceraldehyde inhibited the cytosolic and vacuolar pH responses to illumination. Inhibition was also observed under anaerobiosis. In the absence of DCMU and glyceraldehyde, the extent of the light-dependent vacuolar acidification corresponded closely to the extent of thylakoid energization by light. Because, in contrast to DCMU, glyceraldehyde did not inhibit thylakoid energization while inhibiting the extrachloroplast pH responses, it is concluded that the signal transfer from the chloroplasts to the cytosol which results in increased vacuolar acidification in the light involves metabolites of the Calvin cycle. The observations do not support the view that the cytosolic energy state is increased in the light by the mitochondrial oxidation of the NADH generated during the oxidation of photorespiratory glycine in the mitochondria.
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    URL: http://dx.doi.org/10.1007/BF00197120
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    Factors influencing the capacity for photosynthetic carbon assimilation in barley leaves at low temperatures (1990)
    Springer
    Planta 182 (1990), S. 492-500 
    Details
    ISSN: 1432-2048
    Keywords: Carbon assimilation, photosynthetic ; Hordeum (leaf, carbon assimilation) ; Photosynthesis ; Temperature, low (carbon assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of this work was to examine the effect upon photosynthetic capacity of short-term exposure (up to 10 h) to low temperatures (5° C) of darkened leaves of barley (Hordeum vulgare L.) plants. The carbohydrate content, metabolite status and the photosynthetic rate of leaves were measured at low temperature, high light and higher than ambient CO2. Under these conditions we could detect whether previous exposure of leaves to low temperature overcame the limitation by phosphate which occurs in leaves of plants not previously exposed to low temperatures. The rates of CO2 assimilation measured at 8° C differed by as much as twofold, depending upon the pretreatment. (i) Leaves from plants which had previously been darkened for 24 h had a low content of carbohydrate, had the lowest CO2-assimilation rates at low temperature, and photosynthesis was limited by carbohydrate, as shown by a large stimulation of photosynthesis by feeding glucose, (ii) Leaves from plants which had previously been illuminated for 24 h and which contained large carbohydrate reserves showed an accumulation of phosphorylated intermediates and higher CO2-assimilation rates at low temperature, but nevertheless remained limited by phosphate, (iii) Maximum rates of CO2 assimilation at low temperature were observed in leaves which had intermediate reserves of carbohydrate or in leaves which were rich in carbohydrate and which were also fed phosphate. It is suggested that carbohydrate reserves potentiate the system for the achievement of high rates of photosynthesis at low temperatures by accumulation of photosynthetic intermediates such as hexose phosphates, but that this potential cannot be realised if, at the same time, carbohydrate accumulation is itself leading to feedback inhibition of photosynthesis.
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    URL: http://dx.doi.org/10.1007/BF02341023
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    Control of photosynthesis in leaves as revealed by rapid gas exchange and measurements of the assimilatory force FA (1990)
    Springer
    Planta 182 (1990), S. 513-522 
    Details
    ISSN: 1432-2048
    Keywords: Assimilatory force ; Enzyme regulation ; Gas exchange ; Helianthus (photosynthesis) ; Photosynthesis ; Proton gradient ; Stroma alkalization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The rapid transients of CO2 gas exchange have been measured in leaves ofHelianthus annuus L. In parallel experiments the assimilatory force FA, which is the product of the phosphorylation potential and the redox ratio NADPH/NADP, has been calculated from measured ratios of dihydroxyacetone phosphate to phosphoglycerate in the chloroplast stroma and in leaves. The following results were obtained: (i) When the light-dependent stroma alkalization was measured under steady-state conditions for photosynthesis in air containing 2000 μl · l-1 CO2, alkalization increased with photosynthesis as the quantum flux density (irradiance) was increased. This contrasts to the light-dependent stroma alkalisation measured in dark-adapted leaves during the dark-light transient (Laisk et al. 1989, Planta177, 350–358) which reached a maximum at a quantum flux density far below that necessary to saturate photosynthesis. This maximum was about three times higher than the maximum stroma alkalization at light- and CO2-saturated photosynthesis. (ii) Accurate calculations of the assimilatory force FA require a consideration of the stromal pH. However, under many conditions, changes in the stromal pH resulting from changes in photosynthetic flux can be neglected because they are small. (iii) Stromal ratios of dihydroxyacetone phosphate to phosphoglycerate are generally lower than ratios measured in leaf extracts. The value of FA calculated from stromal metabolites was about 30% lower than FA calculated from cellular metabolites. Still, it appears sufficient for many purposes to calculate FA from metabolite measurements in leaf extracts. (iv) In the light, the catalytic capacity of the photosynthetic apparatus is adjusted to the level of irradiance. The response of carbon assimilation to large increases in irradiance is slow because it requires enzyme activation. Deactivation of the Calvin cycle induced by decreases in irradiance is slower than activation. (v) Changes in catalytic capacity and in the availability or level of substrates such as CO2 alter the flux resistance of the Calvin cycle. A decrease in flux resistance explains why FA often does not increase by much and may actually decrease when carbon flux is increased. Adjustments of flux resistances in the Calvin cycle and of photosystem-II activity in the electron-transport chain permit varying rates of photosynthesis at low levels of ATP and NADPH. As NADP remains available, the danger of over-reduction which leads to photoinactivation of electron transport is minimized.
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    Regulation of photosynthetic sucrose synthesis: a role for calcium? (1990)
    Springer
    Planta 182 (1990), S. 236-243 
    Details
    ISSN: 1432-2048
    Keywords: Calcium ; Partitioning ; Photosynthesis ; Sucrose synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have investigated whether changes of the cytosolic free-calcium concentration could regulate photosynthetic sucrose synthesis. Partially purified enzymes from spinach (Spinacea oleracea L.) leaves were assayed using calcium-EGTA buffers to obtain defined free-calcium concentrations in the low micromolar and submicromolar ranges. These concentrations of calcium did not directly affect sucrose-phosphate synthase activity. They inhibited the cytosolic fructose-1,6-bisphosphatase, acting competitively to magnesium. The Ki for calcium (1.2 μM) was 400-fold lower than the Km for magnesium. To investigate the in-vivo significance of these observations, the Ca2+ antagonists lanthanum (La3+), trifluoperazine, and ruthenium red were supplied to barley leaves via the transpiration stream. All three antagonists selectively inhibited sucrose synthesis: they inhibited 14C incorporation into sucrose at concentrations which did not affect starch synthesis; in low light, partitioning was changed towards starch without altering the rate of photosynthesis; there was a characteristic change in the induction kinetics of photosynthesis; and there was an accumulation of phosphorylated metabolites in the leaf. The detailed changes in metabolite levels indicate that La3+ was acting via inhibition of the fructose-1,6-bisphosphatase, trifluoperazine via blockage of the turnover of inorganic pyrophosphate, and ruthenium red via changes in the activation state (phosphorylation) of sucrose-phosphate synthase. The results are discussed in terms of a possible contribution of calcium to the regulation of carbon metabolism.
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    URL: http://dx.doi.org/10.1007/BF00197117
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    In-vivo and in-vitro synthesis of photosynthetic fructose-1,6-bisphosphatase from pea (Pisum sativum L.) (1990)
    Springer
    Planta 182 (1990), S. 319-324 
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    ISSN: 1432-2048
    Keywords: Fructose-1,6-bisphosphatase (biosynthesis) ; Photosynthesis ; Pisum (photosynthesis)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Etiolated pea (Pisum sativum L. cv. Lincoln) seedlings do not show any capability for the biosynthesis of chloroplast fructose-1,6-bisphosphatase (FBPase), but the rate of biosynthesis of the increases with the pre-illumination time. This light-induced FBPase synthesis appears to be regulated at the transcriptional level, the response of young leaves being greater than that of mature ones. In-vivo labelling experiments demonstrated by immunoprecipitation, followed by sodium dodecyl sulfate electrophoresis and fluorography, the presence of a 49-kilodalton (kDa) band which corresponds to the mature FBPase subunit. In-vitro translation experiments with a wheat-germ synthesizing system and polyadenylated mRNA isolated from illuminated young pea seedlings have demonstrated the appearance of a 59-kDa labelled band corresponding to the precursor of the FBPase basic subunit. When intact pea chloroplasts were added to the above in-vitro incubation mixture, a labelled 49-kDa subunit similar to that of the in-vivo experiments appeared in the organelle under illumination. From these results we can conclude that a 10-kDa transit peptide bound to the translated pea FBPase subunit exists in the cytosol; this transit peptide is lost during passage through the chloroplast envelope, leaving the mature subunit inside the organelle.
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    URL: http://dx.doi.org/10.1007/BF02411381
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    The effects of the spatial pattern of defoliation on regrowth of a tussock grass (1990)
    Springer
    Oecologia 82 (1990), S. 12-17 
    Details
    ISSN: 1432-1939
    Keywords: Tussock grass ; Defoliation ; Canopy structure ; Light interception ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The spatial pattern of foliage removal from a tussock grass can influence regrowth through effects on daily carbon gain (CERd). This field study examined the extent to which tussock photosynthetic responses to different defoliation patterns were associated with changes in whole-canopy attributes (e.g., foliage age structure, canopy light microclimate). During the spring growing season, 60% of the green foliage area was removed from individual Agropyron desertorum tussocks with scissors in different spatial patterns. These patterns represented extremes of defoliation patterns that might be inflicted by natural herbivores. Tussock photosynthesis (per unit foliage area) at high light (2000 μmol photons m−2 s−1 between 400 and 700 nm; P2000) increased following clipping with all defoliation patterns. The increases in P2000 were greater when leaves were removed from low in the tussock (older leaves) than if leaves high in the canopy (younger leaves) were removed. These relative changes of P2000 among clipping patterns paralleled the responses of CERd and regrowth from an earlier study. Furthermore, the changes in P2000 corresponded with increases in the proportion of foliage within the tussocks that was directly illuminated at midday. The greater photosynthesis of tussocks after lower-leaf removal was directly related to a higher proportion of younger foliage and a smaller fraction of foliage shaded within the tussock. In a dense canopy, such as these grass tussocks, the influence of defoliation on whole-canopy attributes may be of primary importance to whole-plant photosynthetic responses.
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    URL: http://dx.doi.org/10.1007/BF00318527
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    Shade adaptation and shade tolerance in saplings of three Acer species from eastern North America (1990)
    Springer
    Oecologia 84 (1990), S. 224-228 
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    ISSN: 1432-1939
    Keywords: Acer saccharum ; A. pensylvanicum ; A. spicatum ; Photosynthesis ; Leaf anatomy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Saplings of three, co-occurring maple species in a mature maple-beech forest differed in a suite of structural and physiological characters that separated the canopy species, Acer, saccharum, from the two subcanopy species, A. pensylvanicum and A. spicatum. Acer saccharum had both more dense wood and tougher and heavier but thinner leaves than the subcanopy species. Acer pensylvanicum had the largest, lightest leaves with high stomatal density and its canopy architecture was the most effective in terms of leaf display for light interception. Acer spicatum had weaker wood similar to that of A. pensylvanicum but also small, soft and relatively poorly displayed leaves. Both subcanopy species maintained marginally higher average rates of photosynthesis over the growing season in the understory environment. We consider juvenile A. saccharum only shade-tolerant, capable of persisting through long periods in the closed canopy until a gap occurs but not specifically adapted to the understory environment. Juvenile A. sacchrum appears to be constrained functionally by the requirements set by the canopy environment that adults will occupy. Characters such as high wood density are already expressed in the understory sapling; this investment in denser wood slows the growth of saplings, but is necessary for structural reasons in the adult. Juvenile A. saccaharum have morphological and photosynthetic characters better suited to gas exchange and extension growth under the increased photon flux densities in large forest gaps, characteristics that will also be advantageous in the sunlit canopy environment of adults. Both subcanopy maples appear to be more truly shade-adapted, although in somewhat different ways. Acer pensylvanicum has characteristics that enhance the potential for capture and utilization of sunflecks and is able to sustain higher growth rates than A. saccharum in the shaded subcanopy environment. Acer spicatum shares some shade-adapted features with A. pensylvanicum, and its habit of lateral spread through stem layering may confer an additional advantage in foraging for small light gaps.
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    URL: http://dx.doi.org/10.1007/BF00318275
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    Carbon isotope discrimination by plants follows latitudinal and altitudinal trends (1991)
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    Oecologia 88 (1991), S. 30-40 
    Details
    ISSN: 1432-1939
    Keywords: Alpine ecology ; CO2 ; Climate ; δ13C ; Leaf structure ; Oxygen ; Photosynthesis ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In an earlier paper we provided evidence that carbon isotope discrimination during photosynthesis of terrestrial C3 plants decreases with altitude, and it was found that this was associated with greater carboxylation efficiency at high altitudes. Changing partial pressures of CO2 and O2 and changing temperature are possible explanations, since influences of moisture and light were reduced to a minimum by selective sampling. Here we analyse plants sampled using the same criteria, but from high and low altitudes along latitudinal gradients from the equator to the polar ends of plant distribution. These data should permit separation of the pressure and temperature components (Fig. 1). Only leaves of fully sunlit, non-water-stressed, herbaceous C3 plants are compared. The survey covers pressure differences of 400 mbar (ca. 5000 m) and 78 degrees of latitude (ca 25 K of mean temperature of growth period). When habitats of similar low temperature (i.e. high altitude at low latitude and low altitude at polar latitude) are compared, discrimination increases towards the pole (with decreasing altitude and thus increasing atmospheric pressure). Latitudinally decreasing temperature at almost constant atmospheric pressure (samples from low altitude) is associated with a decrease in discrimination. So, polar low-altitude plants have δ13C values half way between humid tropical lowland and tropical alpine plants. It is unlikely that latitudinal changes of the light regime had an effect, since low and high altitude plants show contrasting latitudinal trends in δ13C although local altitudinal differences in overall light consumption were small. These results suggest that both temperature and atmospheric pressure are responsible for the altitudinal trends in 13C discrimination. Temperature effects may partly be related to increased leaf thickness (within the same leaf type) in cold environments. Theoretical considerations and laboratory experiments suggest that it is the oxygen partial pressure that is responsible for the pressure related change in discrimination. The study also provided results of practical significance for the use of carbon isotope data. Within a community of C3 plants, discrimination in species of similar life form, exposed to similar light, water and ambient CO2 conditions ranges over 4‰, with standard deviations for 10–30 species of ±0.6 to 1.2‰. This natural variation has to be taken into account by using a sufficient sample size and standardization of sampling in any attempt at ecological site characterization using carbon isotope data. Evidence of a pronounced genotypic component of this variation in 13C discrimination in wild C3 plant species is provided. Correlations with dry matter partitioning, mesophyll thickness and nitrogen content are also present.
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    Comparative life history and physiology of two understory Neotropical herbs (1991)
    Springer
    Oecologia 88 (1991), S. 263-273 
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    ISSN: 1432-1939
    Keywords: Drought ; Life history ; Marantaceae ; Photosynthesis ; Treefall gaps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Demography and physiology of two broad-leaved understory tropical herbs (Marantaceae) were studied in gaps and shaded understory in large-scale irrigated and control treatments during the dry season at Barro Colorado Island (BCI), Panama. Because photosynthetic acclimation potential may not predict light environments where tropical species are found, we studied a suite of physiological features to determine if they uniquely reflect the distribution of each species. Calathea inocephala and Pleiostachya pruinosa grow and reproduce in gaps, persist in shade, and have equivalent rates of leaf production. Calathea leaves survived 2 to 3 times as long as leaves of Pleiostachya and plants of Pleiostachya were 6 to 8 times more likely to die as plants of Calathea during 3.5 years of study. Pleiostachya had lowest survival in shade and when not irrigated during the dry season, while Calathea survived well in both habitats and both treatments. Pleiostachya had higher photosynthetic capacity and stomatal conductance than Calathea and acclimated to gaps by producing leaves with higher photosynthetic capacity. Calathea had lower mesophyll CO2 concentrations than Pleiostachya. Both species had similar dark respiration rates and light compensation points, and water-use and nitrogen-use efficiencies were inversely related between species. Species showed no differences in leaf osmotic potentials at full turgor. Calathea roots were deeper and had tuberous swellings. Leaf-level assimilation and potential water loss are consistent with where these species are found, but photosynthetic acclimation to high light does not reflect both species' abilities to grow and reproduce in gaps. Pleiostachya's gap-dependent, rapid growth and reproduction require high rates of carbon gain in short-lived leaves, which can amortize their cost quickly. High rates of water loss are associated with reduced longevity during drought. Calathea's roots may confer greater capacitance, while its leaves are durable, long-lived and have lower water loss, permitting persistence long after gap closure.
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    URL: http://dx.doi.org/10.1007/BF00320821
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    Remote sensing of the xanthophyll cycle and chlorophyll fluorescence in sunflower leaves and canopies (1990)
    Springer
    Oecologia 85 (1990), S. 1-7 
    Details
    ISSN: 1432-1939
    Keywords: Chlorophyll fluorescence ; Photosynthesis ; Remote sensing ; Sunflower (Helianthus annuus) ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sudden illumination of sunflower (Helianthus annuus L. cv. CGL 208) leaves and canopies led to excess absorbed PFD and induced apparent reflectance changes in the green, red and near-infrared detectable with a remote spectroradiometer. The green shift, centered near 531 nm, was caused by reflectance changes associated with the de-epoxidation of violaxanthin to zeaxanthin via antheraxanthin and with the chloroplast thylakoid pH gradient. The red (685 nm) and near-infrared (738 nm) signals were due to quenching of chlorophyll fluorescence. Remote sensing of shifts in these spectral regions provides non-destructive information on in situ photosynthetic performance and could lead to improved techniques for remote sensing of canopy photosynthesis.
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    URL: http://dx.doi.org/10.1007/BF00317336
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    Leaf life spans in wild perennial herbaceous plants: a survey and attempts at a functional interpretation (1992)
    Springer
    Oecologia 89 (1992), S. 10-16 
    Details
    ISSN: 1432-1939
    Keywords: Altitude ; Longevity ; Nitrogen ; Photosynthesis ; Specific leaf area
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf longevity in 29 herbaceous plant species of Central Europe was studied by inspecting tagged leaves at weekly intervals. About half of the species are elements of the lowland meadow flora, the other half comprises a representative sample of species from the highest sites where vascular plants grow in the Alps. Shaded and water-stressed sites were avoided. Overall mean leaf longevity did not differ significantly between sites and amounted to 71±5 days at low and 68±4 days at high altitude. Leaf life spans ranged (with no clear altitudinal trend) from 41 to 95 days. Low-altitude forbs and grasses produced several leaf cohorts during their growth period, while most alpine species produced only one. Correlations were found between leaf duration and percent nitrogen content and carbon-cost/carbon-gain ratios, but not with leaf dry mass per unit leaf area and photosynthetic capacity alone. As leaf life spans increase, more C tends to be invested per unit CO2 uptake and less N is invested per unit invested C. Thus, mass relationships rather than area relationships seem to be linked to leaf life span in these species, suggesting that leaf duration is associated with properties other than the efficiency of light utilization (e.g. mechanical strength, herbivory or pathogen resistance). It seems that the explanations of leaf duration that have been developed for evergreen/deciduous plants and for plants along steep light gradients do not apply to the variable life spans in leaves of perennial herbaceous plants of open habitats.
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    The effect of light quantity and quality during development on the photosynthetic characteristics of six Australian rainforest tree species (1991)
    Springer
    Oecologia 87 (1991), S. 110-117 
    Details
    ISSN: 1432-1939
    Keywords: Rainforest ; Photosynthesis ; Dark respiration ; Growth irradiance ; R/FR ratio
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedlings of six subtropical rainforest tree species representing early (Omalanthus populifolius, Solanum aviculare), middle (Duboisia myoporoides, Euodia micrococca) and late (Acmena ingens, Argyrodendron actinophyllum) successional stages in forest development were grown in a glasshouse, under four levels of neutral shade (60%, 15%, 5%, 1% of photosynthetically active radiation (PAR) in incident sunlight) and three levels of selectively filtered shade (producing 15%, 5%, 1% of PAR). This design served to analyse the interactions between reduced photon flux density (PFD) and reduced red/far-red (R/FR) ratio in their effects on selected photosynthetic characteristics of each species. The light-saturated rate of photosynthesis was significantly influenced by growth irradiance in five of the six species, with all of these showing a non-linear decrease in maximum assimilation rate from 60% down to 1% PAR. The degree of acclimation to this range was not clearly related to the successional status of the species. Dark respiration was more sensitive to growth irradiance in the early- and mid-stage species than in the late-stage species. Although levels of dark respiration were clearly greater in leaves of early- and mid-stage species from the highest light levels, differences between successional groups were negligible at 1% PAR. Growth in filtered shade, typical of that beneath a closed canopy, resulted in lower photosynthetic capacities and quantum yields in those species which did respond. Although dark respiration rates were more sensitive to filtered shade in the early-stage than in the late-stage species, there was no evidence from other gas exchange characteristics to suggest that overall sensitivity to light quality (as characterised by the R/FR ratio) is greater in early successional-stage species.
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    URL: http://dx.doi.org/10.1007/BF00323788
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    Mineral nutrient deficiency increases the sensitivity of photosynthesis to sulphur dioxide in needles of a coniferous tree, Abies nordmanniana (1992)
    Springer
    Oecologia 90 (1992), S. 70-73 
    Details
    ISSN: 1432-1939
    Keywords: Abies ; Mineral deficiency ; Photosynthesis ; Sulphur dioxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Abies nordmanniana (Stev.) Spach was cultivated in rooting media either rich in nutrients (control) or low in magnesium (low Mg) or low in magnesium and nitrogen (low Mg-N), respectively. Intact, attached needles were exposed, in the light (460 μmol photons m-2 s-1), to an atmosphere containing 1 ppm SO2 for 5 h. Measurements of light- and CO2-saturated rates of photosynthetic O2 evolution, A max, were performed before and after SO2 treatments. In needles from well fertilized plants, A max was high (about 50 μmol m-2 s-1) and was not affected by SO2. Needles from low-Mg and low-Mg-N plants had lower photosynthetic rates and showed a marked decline in A max in response to the SO2 treatment. Stomatal conductance was similar in the three groups of plants during SO2 treatments.
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    Temperate rainforest lichens in New Zealand: high thallus water content can severely limit photosynthetic CO2 exchange (1993)
    Springer
    Oecologia 95 (1993), S. 303-313 
    Details
    ISSN: 1432-1939
    Keywords: Lichen ; Water content ; Photosynthesis ; Rainforest ; Diffusive resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract CO2 exchange rate in relation to thallus water content (WC, % of dry weight) was determined for 22 species of lichens, mainly members of the genera Pseudocyphellaria and Sticta, from a temperate rainforest, Urewere National Park, New Zealand. All data were obtained in the field, either using a standard technique in which the lichens were initially wetted (soaked or sprayed, then shaken) and allowed to slowly dry, or from periodic measurements on samples that were continuously exposed in their natural habitat. A wide range of WC was found, with species varying from 357 to 3360% for maximal WC in the field, and from 86 to 1300% for optimal WC for photosynthesis. Maximal WC for lichens, wetted by the standard technique, were almost always much less than the field maxima, due to the presence of water on the thalli. The relationships between CO2 exchange rate and WC could be divided into four response types based on the presence, and degree, of depression of photosynthesis at high WC. Type A lichens showed no depression, and Type B only a little at maximal WC. Type C had a very large depression and, at the highest WC, CO2 release could occur even in the light. Photosynthetic depression commenced soon after optimal WC was reached. Type D lichens showed a similar depression but the response curve had an inflection so that net photosynthesis was low but almost constant, and never negative, at higher WC. There was little apparent relationship between lichen genus or photobiont type and the response type. It was shown that high WC does limit photosynthetic CO2 uptake under natural conditions. Lichens, taken directly from the field and allowed to dry under controlled conditions, had net photosynthesis rates that were initially strongly inhibited but rose to an optimum, before declining at low WC. The limiting effects of high WC were clearly shown when, under similar light conditions, severe photosynthetic depression followed a brief, midday, rain storm. Over the whole measuring period the lichens were rarely at their optimal WC for photosynthesis, being mostly too wet or, occasionally, too dry. Photosynthetic performance by the lichens exposed in the field was similar to that expected from the relationship between the photosynthetic rate and WC established by the standard procedure.
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    CO2 environment, microclimate and photosynthetic characteristics of the moss Hylocomium splendens in a subarctic habitat (1992)
    Springer
    Oecologia 92 (1992), S. 23-29 
    Details
    ISSN: 1432-1939
    Keywords: CO2 environment ; Photosynthesis ; Microclimate ; Moss ; Hylocomium splendens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In order to document the natural CO2 environment of the moss Hylocomium splendens, and ascertain whether or not the moss was adapted to this, and its interactions with other microenvironmental factors, two studies were carried out. Firstly, the seasonal variations of CO2 concentration, photosynthetically active radiation (PAR), tissue water content and temperature were measured in the natural microenvironment of H. splendens in a subarctic forest during the summer period (July–September). Secondly, the photosynthetic responses of the species to controlled CO2 concentrations, PAR, temperature, and hydration were measured in the laboratory. CO2 concentrations around the upper parts of the plant, when PAR was above the compensation point (30 μmol m−2 s−1), were mostly between 400 and 450 ppm. They occasionally increased up to 1143 ppm for short periods. PAR flux densities below saturating light levels for photosynthesis (100 μmol m−2 s−1), occurred during 65% (July), 76% (August) and 96% (September) of the hours of the summer period. The temperature optimum of photosynthesis was 20° C: this temperature coincided with PAR above the compensation point during 5%, 6% and 0% of the time in July, August and September, respectively. Optimal hydration of tissues was infrequent. Hence PAR, temperature and water limit CO2 uptake for most of the growing season. Our data suggest that the higher than normal ambient CO2 concentration in the immediate environment of the plant counteracts some of the limitations in PAR supply that it experiences in its habitat. This species already experiences concentrations of atmospheric CO2 predicted to occur over the next 50 years.
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    Canopy structure and vertical patterns of photosynthesis and related leaf traits in a deciduous forest (1993)
    Springer
    Oecologia 96 (1993), S. 169-178 
    Details
    ISSN: 1432-1939
    Keywords: Acer saccharum ; Photosynthesis ; Forest canopy ; Sugar maple ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Canopy structure and light interception were measured in an 18-m tall, closed canopy deciduous forest of sugar maple (Acer saccharum) in southwestern Wisconsin, USA, and related to leaf structural characteristics, N content, and leaf photosynthetic capacity. Light attenuation in the forest occurred primarily in the upper and middle portions of the canopy. Forest stand leaf area index (LAI) and its distribution with respect to canopy height were estimated from canopy transmittance values independently verified with a combined leaf litterfall and point-intersect method. Leaf mass, N and A max per unit area (LMA, N/area and A max/area, respectively) all decreased continuously by over two-fold from the upper to lower canopy, and these traits were strongly correlated with cumulative leaf area above the leaf position in the canopy. In contrast, neither N concentration nor A max per unit mass varied significantly in relation to the vertical canopy gradient. Since leaf N concentration showed no consistent pattern with respect to canopy position, the observed vertical pattern in N/area is a direct consequence of vertical variation of LMA. N/area and LMA were strongly correlated with A max/area among different canopy positions (r2=0.81 and r2=0.66, respectively), indicating that vertical variation in area-based photosynthetic capacity can also be attributed to variation in LMA. A model of whole-canopy photosynthesis was used to show that observed or hypothetical canopy mass distributions toward higher LMA (and hence higher N/area) in the upper portions of the canopy tended to increase integrated daily canopy photosynthesis over other LMA distribution patterns. Empirical relationships between leaf and canopy-level characteristics may help resolve problems associated with scaling gas exchange measurements made at the leaf level to the individual tree crown and forest canopy-level.
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    URL: http://dx.doi.org/10.1007/BF00317729
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    Photosynthetic induction responses of two rainforest tree species in relation to light environment (1993)
    Springer
    Oecologia 96 (1993), S. 193-199 
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    ISSN: 1432-1939
    Keywords: Costa Rica ; Hemispherical photography ; Photosynthesis ; Rain forest ; Sunflecks
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthetic induction of in situ saplings of two Costa Rican rainforest tree species wre compared in relation to their light environment, using infrared gas analysis and hemispherical photography. The species studied were Dipteryx panamensis, a climax species found in bright microsites, and Cecropia obtusifolia, a pioneer species. In the morning, when leaves were most responsive, induction time necessary to reach 90% of the lightsaturated rate of photosynthesis was on average 16 min for Dipteryx and 10 min for Cecropia. However, induction times for both species increased in the afternoon resulting in shorter daily average induction times for Dipteryx than for Cecropia. Dipteryx also maintained higher levels of induction for a longer period under low light conditions than did Cecropia. The two species differed in the way they adjusted to light availability. Dipteryx saplings growing in shady sites had faster rates of induction than saplings growing in bright sites, with no difference in light-saturated photosynthetic rate. In contrast, Cecropia saplings growing in bright sites had higher light-saturated photosynthetic rates than saplings growing in shady sites, with no difference in rates of induction. Dipteryx appears to exploit temporal variation in light availability by refining the quickness of the induction response to the light environment, while Cecropia adjusts its scale of exploitation by realizing a higher lightsaturated photosynthetic rate in sites of higher light.
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    URL: http://dx.doi.org/10.1007/BF00317732
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    Photoinhibition as a control on photosynthesis and production of Sphagnum mosses (1993)
    Springer
    Oecologia 96 (1993), S. 200-207 
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    ISSN: 1432-1939
    Keywords: Photosynthesis ; Production ; Sphagnum moss ; Photoinhibition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of high light intensity on photosynthesis and growth of Sphagnum moss species from Alaskan arctic tundra was studied under field and laboratory conditions. Field experiments consisted of experimental shading of mosses at sites normally exposed to full ambient irradiance, and removal of the vascular plant canopy from above mosses in tundra water track habitats. Moss growth was then monitored in the experimental plots and in adjacent control areas for 50 days from late June to early August 1988. In shaded plots total moss growth was 2–3 times higher than that measured in control plots, while significant reductions in moss growth were found in canopy removal plots. The possibility that photoinhibition of photosynthesis might occur under high-light conditions and affect growth was studied under controlled laboratory conditions with mosses collected from the arctic study site, as well as from a temperate location in the Sierra Nevada, California. After 2 days of high-light treatment (800 μmol photons m−2 s−1) in a controlled environmental chamber, moss photosynthetic capacity was significantly lowered in both arctic and temperate samples, and did not recover during the 14-day experimental period. The observed decrease in photosynthetic capacity was correlated (r 2=0.735, P〈0.001) with a decrease in the ratio of variable to maximum chlorophyll fluorescence (F v/F m) in arctic and temperate mosses. This relationship indicates photoinhibition of photosynthesis in both arctic and temperate mosses at even moderately high light intensities. It is suggested that susceptibility to photoinhibition and failure to photoacclimate to higher light intensities in Sphagnum spp. may be related to low tissue nitrogen levels in these exclusively ombrotrophic plants. Photoinhibition of photosynthesis leading to lowered annual carbon gain in Sphagnum mosses may be an important factor affecting CO2 flux at the ecosystem level, given the abundance of these plants in Alaskan tussock tundra.
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    URL: http://dx.doi.org/10.1007/BF00317733
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    Relative growth rate in relation to physiological and morphological traits for northern hardwood tree seedlings: species, light environment and ontogenetic considerations (1993)
    Springer
    Oecologia 96 (1993), S. 219-231 
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    ISSN: 1432-1939
    Keywords: Relative growth rate ; Leaf allocation ; Photosynthesis ; Respiration ; Ontogeny
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of ontogeny, light environment and species on relationships of relative growth rate (RGR) to physiological and morphological traits were examined for first-year northern hardwood tree seedlings. Three Betulaceae species (Betula papyrifera, Betula alleghaniensis and Ostrya virginiana) were grown in high and low light and Quercus rubra and Acer saccharum were grown only in high light. Plant traits were determined at four ages: 41, 62, 83 and 104 days after germination. In high light (610 μmol m−2 s−1 PPFD), across species and ages, RGR was positively related to the proportion of the plant in leaves (leaf weight ratio, LWR; leaf area ratio, LAR), in situ rates of average canopy net photosynthesis (A) per unit mass (Amass) and per unit area (Aarea), and rates of leaf, stem and root respiration. In low light (127 μmol m−2 s−1 PPFD), RGR was not correlated with Amass and Aarea whereas RGR was positively correlated with LAR, LWR, and rates of root and stem respiration. RGR was negatively correlated with leaf mass per area in both high and low light. Across light levels, relationships of CO2 exchange and morphological characteristics with RGR were generally weaker than within light environments. Moreover, relationships were weaker for plant parameters containing a leaf area component (leaf mass per area, LAR and Aarea), than those that were solely mass-based (respiration rates, LWR and Amass). Across light environments, parameters incorporating the proportion of the plant in leaves and rates of photosynthesis explained a greater amount of variation in RGR (e.g. LWR*Amass, R2=0.64) than did any single parameter related to whole-plant carbon gain. RGR generally declined with age and mass, which were used as scalars of ontogeny. LWR (and LAR) also declined for seven of the eight species-light treatments and A declined in four of the five species in high light. Decreasing LWR and A with ontogeny may have been partially responsible for decreasing RGR. Declines in RGR were not due to increased respiration resulting from an increase in the proportion of solely respiring tissue (roots and stems). In general, although LWR declined with ontogeny, specific rates of leaf, stem, and root respiration also decreased. The net result was that whole-plant respiration rates per unit leaf mass decreased for all eight treatments. Identifying the major determinants of variation in growth (e.g. LWR*Amass) across light environments, species and ontogeny contributes to the establishment of a framework for exploring limits to productivity and the nature of ecological success as measured by growth. The generality of these relationships both across the sources of variation we explored here and across other sources of variation in RGR needs further study.
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    URL: http://dx.doi.org/10.1007/BF00317735
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    Coordination theory of leaf nitrogen distribution in a canopy (1993)
    Springer
    Oecologia 93 (1993), S. 63-69 
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    ISSN: 1432-1939
    Keywords: Canopy structure ; Coordination ; Nitrogen allocation ; Optimization ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It has long been observed that leaf nitrogen concentrations decline with depth in closed canopies in a number of plant communities. This phenomenon is generally believed to be related to a changing radiation environment and it has been suggested by some researchers that plants allocate nitrogen in order to optimize total whole canopy photosynthesis. Although optimization theory has been successfully utilized to describe a variety of physiological and ecological phenomena, it has some shortcomings that are subject to criticism (e.g., time constraints, oversimplifications, lack of insights, etc.). In this paper we present an alternative to the optimization theory of plant canopy nitrogen distribution, which we term coordination theory. We hypothesize that plants allocate nitrogen to maintain a balance between two processes, each of which is dependent on leaf nitrogen content and each of which potentially limits photosynthesis. These two processes are defined as Wc, the Rubiscolimited rate of carboxylation, and Wj, the electron transport-limited rate of carboxylation. We suggest that plants allocate nitrogen differentially to, leaves in different canopy layers in such a way that Wc and Wj remain roughly balanced. In this scheme, the driving force for the allocation of nitrogen within a canopy is the difference between the leaf nitrogen content that is required to bring Wc and Wj into balance and the current nitrogen content. We show that the daily carbon assimilation of a canopy with a nitrogen distribution resulting from this internal coordination of Wc and Wj is very similar to that obtained using optimization theory.
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    URL: http://dx.doi.org/10.1007/BF00321192
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    Phenotypic plasticity in response to nitrate supply of an inherently fast-growing species from a fertile habitat and an inherently slow-growing species from an infertile habitat (1993)
    Springer
    Oecologia 96 (1993), S. 548-554 
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    ISSN: 1432-1939
    Keywords: Biomass allocation ; Nitrogen supply ; Phenotypic plasticity ; Photosynthesis ; Root distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aim of the present study was to investigate possible differences in plasticity between a potentially fast-growing and a potentially slow-growing grass species. To this end, Holcus lanatus (L.) and Deschampsia flexuosa (L.) Trin., associated with fertile and infertile habitats, respectively, were grown in sand at eight nitrate concentrations. When plants obtained a fresh weight of approximately 5 g, biomass allocation, specific leaf area, the rate of net photosynthesis, the organic nitrogen concentration of various plant parts and the root weight at different soil depths were determined. There were linear relationships between the morphological and physiological features studied and the In-transformed nitrate concentration supplied, except for the specific leaf area and root nitrogen concentration of H. lanatus, which did not respond to the nitrate concentration. The root biomass of H. lanatus was invariably distributed over the soil layers than that of D. flexuosa. However, D. flexuosa allocated more root biomass to lower soil depths with decreasing nitrate concentration, in contrast to H. lanatus, which did not respond. The relative response to nitrate supply, i.e. the value of a character at a certain nitrate level relative to the value of that character at the highest nitrate supply, was used as a measure for plasticity. For a number of parameters (leaf area ratio, root weight ratio, root nitrogen concentration, vertical root biomass distribution and rate of net photosynthesis per unit leaf weight) the potentially slow-growing D. flexuosa exhibited a higher phenotypic plasticity than the potentially fast-growing H. lanatus. These findings are in disagreement with current literature. Possible explanations for this discrepancy are discussed in terms of differences in experimental approach as well as fundamental differences in specific traits between fast- and slow-growing grasses.
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    URL: http://dx.doi.org/10.1007/BF00320512
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    Growth, biomass distribution and CO2 exchange of northern hardwood seedlings in high and low light: relationships with successional status and shade tolerance (1993)
    Springer
    Oecologia 94 (1993), S. 7-16 
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    ISSN: 1432-1939
    Keywords: Relative growth rate ; Photosynthesis ; Respiration ; Biomass distribution ; Shade tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The physiology, morphology and growth of first-year Betula papyrifera Marsh., Betula alleghaniensis Britton, Ostrya virginiana (Mill.) K. Koch, Acer saccharum Marsh., and Quercus rubra L. seedlings, which differ widely in reported successional affinity and shade tolerance, were compared in a controlled high-resource environment. Relative to late-successional, shade-tolerant Acer and Ostrya species, early-successional, shade-intolerant Betula species had high relative growth rates (RGR) and high rates of photosynthesis, nitrogen uptake and respiration when grown in high light. Fire-adapted Quercus rubra had intermediate photosynthetic rates, but had the lowest RGR and leaf area ratio and the highest root weight ratio of any species. Interspecific variation in RGR in high light was positively correlated with allocation to leaves and rates of photosynthesis and respiration, and negatively related to seed mass and leaf mass per unit area. Despite higher respiration rates, early-successional Betula papyrifera lost a lower percentage of daily photosynthetic CO2 gain to respiration than other species in high light. A subset comprised of the three Betulaceae family members was also grown in low light. As in high light, low-light grown Betula species had higher growth rates than tolerant Ostrya virainiana. The rapid growth habit of sarly-successional species in low light was associated with a higher proportion of biomass distributed to leaves, lower leaf mass per unit area, a lower proportion of biomass in roots, and a greater height per unit stem mass. Variation in these traits is discussed in terms of reported species ecologies in a resource availability context.
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    URL: http://dx.doi.org/10.1007/BF00317294
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    Mid-season gas exchange of an alpine grassland under elevated CO2 (1994)
    Springer
    Oecologia 98 (1994), S. 429-435 
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    ISSN: 1432-1939
    Keywords: Climate change ; Carbon dioxide ; Altitude ; Photosynthesis ; Water loss
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ecosystem net CO2 uptake, evapotranspiration (ET) and night-time CO2 efflux were measured in an alpine grassland dominated by Carex curvula, treated with doubled ambient partial pressure of CO2 via open-top chambers. One quarter of the plots were treated with mineral nutrients to simulate the effect of lowland nitrogen deposition rates. Depending upon fertilizer supply, ecosystem net CO2 uptake per ground area in full sunlight (NCEmax) was 41–81% higher in open-top chambers supplied with doubled ambient partial pressure (p a) of CO2 than in plots receiving ambient CO2. Short-term reversals of the CO2 level suggest that the extent of downward adjustment of canopy photosynthesis under elevated CO2 was 30–40%. ET tended to decline, while water use efficiency (WUE), expressed as the NCEmax:ET ratio, increased more than twofold under elevated CO2. Night-time ecosystem CO2 efflux did not respond to changes in CO2 p a. NCEmax and night-time CO2 efflux were more responsive to mineral fertilizer than the doubling of CO2. This suggests that in these alpine plant communities, atmospheric nutrient input may induce equal or greater effects on gas exchange than increased CO2.
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    URL: http://dx.doi.org/10.1007/BF00324233
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    Above- and below-ground environmental influences on leaf conductance ofCeanothus thyrsiflorus growing in a chaparral environment: drought response and the role of abscisic acid (1994)
    Springer
    Oecologia 99 (1994), S. 306-314 
    Details
    ISSN: 1432-1939
    Keywords: Abscisic acid ; Chaparral ; Ceanothus thyrsiflorus ; Conductance ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Small shrubs ofCeanothus thyrsiflorus were grown in 19-1 pots irrigated under natural conditions in a chaparral region of Southern California and then subjected to soil drying. Characteristics of leaf gas exchange, leaf water potential, and concentrations of the stress hormone abscisic acid in the xylem sap, ABAxyl, were determined at various stages of drought. Diurnal changes in conductance were strongly correlated with leaf net photosynthesis rate, which provides an effective, integrative predictor of above-ground climate effects on conductance. In drought conditions, ABAxyl concentration increased. Increases in the concentration range of 50–500 nmol/l appeared to induce stomatal closure, restricting water loss and carbon dioxide uptake. When the momentary water potential is related to ABAxyl, ABA appeared to increase significantly only after a threshold of approximately −1.5 MPa was exceeded. At less negative water potentials, large variation in ABAxyl in the 50–1000 nmol/l range occurred for all water-potential values, because ABAxyl remains relatively constant over diurnal courses as water potentials decrease and then recover. When the water potential became more negative than −1.5 MPa, ABAxyl concentrations occurred between approximately 500 and 10 000 nmol/l and even greater in isolated cases. An approximately linear relationship is recognizable between ABAxyl and momentary water potential in this range because in plants under drought conditions, ABAxyl increases during the course of the day as water potential decreases. Increases in ABAxyl in the high concentration range were associated with relatively minor additional restrictions in gas exchange, but they might contribute to improved water use efficiency and explain diurnal changes in the potential for stomatal opening that have been observed in Mediterranean sclerophyllous species. When we examined long-term seasonal change in the response of irrigated plants, changes in average daily temperature greater than 10°C occurred (also associated with shifts in relative humidity and radiation input), which apparently led to small changes in predawn water potential in the −0.1 to −0.7 MPa range. Increases in ABAxyl occurred that were in turn negatively correlated with daily maximum leaf conductance. Thus, chaparral shrubs under non-drought conditions seem to sense even small changes in environmental conditions, in our opinion most probably due to initial drying of the uppermost soil and synthesis of ABA in the shallow roots. The results support the hypothesis that information of photosynthesis rate and predawn water potential may be used as primary variables to predict canopy conductance of Mediterranean sclerophyll shrub vegetation.
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    URL: http://dx.doi.org/10.1007/BF00627743
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    Long term effects of naturally elevated CO2 on mediterranean grassland and forest trees (1994)
    Springer
    Oecologia 99 (1994), S. 343-351 
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    ISSN: 1432-1939
    Keywords: Carbohydrates ; Global change ; Natural CO2 springs ; Leaf nitrogen ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the carbon supply status in species-rich mediterranean plant communities growing in a bowl-shaped 1-ha “CO2 spring” area near Sienna, Italy. A geothermic “lime-kiln” has provided these communities, for as long as historical records are available, with pure CO2 that mixes with ambient air at canopy level to daytime means of 500–1000 ppm CO2. Immediately outside the spring area similar plant communities are growing on similar substrate, and in the same climate, but under ca. 355 ppm CO2. We found no evidence that plants in the CO2 spring area grow faster, flower earlier or become larger. However, we found very large differences in tissue quality among the 40 species studied inside and outside the spring area. Depending on weather conditions, the mean concentration of total non-structural carbohydrates (TNC, sugars and starch) in leaves of herbaceous plants was 38–47% higher in the spring area. Fast growing ruderals growing on garden soil inside and outside the spring area show the same response. Among trees, leaves of the deciduousQuercus pubscens contain twice as much TNC inside as outside the vent area, whereas evergreenQ. ilex leaves show no significant difference. TNC levels in branch wood paralleled leaf values. TNC in shade leaves was also higher. Elevated CO2 had no effect on the sugar fraction, therefore differences in TNC are due to starch accumulation. Leaf nitrogen concentration decreases under elevated CO2. These observations suggest that the commonly reported TNC accumulation and N depletion in leaves growing under elevated CO2 are not restricted to the artificial conditions of short-term CO2 enrichment experiments but persist over very long periods. Such an alteration of tissue composition can be expected to occur in other plant communities also if atmospheric CO2 levels continue to rise. Effects on food webs and nutrient cycling are likely.
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    Ecophysiological consequences of non-random leaf orientation in the prairie compass plant, Silphium laciniatum (1990)
    Springer
    Oecologia 82 (1990), S. 180-186 
    Details
    ISSN: 1432-1939
    Keywords: Compass plant ; Leaf inclination ; Leaf azimuth ; Photosynthesis ; Water use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The prairie compass plant (Silphium laciniatum L.) has vertical leaves that are characteristically oriented in a north-south plane (i.e., the flat surfaces of the lamina face east and west). We explored the consequences of this orientation by determining basic photosynthetic and water use characteristics in response to environmental factors and by determining total daily photosynthesis and water use of leaves held in different orientations. Average maximum CO2 exchange rate (CER) of leaves near Ames, IA was constant at 22 micromol m−2 s−1 from May through August and then declined. CER did not exhibit a distinct lightsaturation point. CER at photon flux densities near full sunlight was constant from 22 to 35°C leaf temperature but declined at higher temperatures. However, leaf temperatures rarely exceed 35°C during the growing season. There was no change in the pattern of response of CER to temperature over the growing season. We constrained leaves to face east-west (EW,=natural), to face north-south (NS), or to be horizontal (HOR) on eight days in 1986–1988. EW leaves had the highest light interception, leaf temperatures, CER, and transpiration early and late in the day, whereas HOR leaves had the highest values in the middle of the day. Integrations of CER and transpiration over the eight daytime periods showed EW and HOR leaves to have equivalent carbon gain, higher than that of NS leaves. HOR leaves had the highest daily transpiration. Daily water use efficiency (WUE, carbon gained/water lost) was always highest in EW leaves, with the HOR leaves having 16% lower WUE and NS leaves having 33% lower WUE. The natural orientation of compass plant leaves results in equivalent or higher carbon gain and in increased WUE when compared to leaves with other possible orientations; this is likely to have a selective advantage in a prairie environment.
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    Seasonal changes in shoot regrowth potential in Calamagrostis canadensis (1991)
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    Oecologia 85 (1991), S. 596-602 
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    ISSN: 1432-1939
    Keywords: Carbohydrate ; Regrowth ; Disturbance ; Grass ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A series of laboratory experiments was conducted to examine seasonal change in shoot regrowth potential following disturbance in Calamagrostis canadensis. On several dates during the 1988 and 1989 growing seasons, soil cores were collected from field sites dominated by this grass. Shoot regrowth from cores after clipping at the soil surface was monitored under dark or light laboratory conditions at 20°C. seasonal changes in field concentrations of total nonstructural carbohydrate and nitrogen in rhizomes largely accounted for the observed seasonal change in etiolated regrowth potential of shoots in laboratory experiments. In contrast, shoot regrowth potential in the light showed a very different seasonal pattern. The ratio of shoot biomass regrowth 20 d after clipping in the light versus dark treatment showed a gradual seasonal decrease from 12:1 in the early May experiment to near 1:1 in the September experiment. However, the rate of photosynthesis of regrowing shoots in the light was highest in experiments conducted late in the growing season. This may indicate a strong seasonal decrease in the proportion of current photosynthate of regrowing shoots that is allocated to new shoot growth. Alternatively, mobilization of rhizome carbohydrate reserves for shoot regrowth may have been inhibited during the re-establishment of photosynthesis in the light treatment. Either mechanism would explain why shoot regrowth in the light is poorly correlated with levels of belowground carbohydrate reserves, even under controlled laboratory conditions.
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    Autumnal leaf conductance and apparent photosynthesis by saplings and sprouts in a recently disturbed northern hardwood forest (1990)
    Springer
    Oecologia 84 (1990), S. 93-98 
    Details
    ISSN: 1432-1939
    Keywords: Forest disturbance ; Hubbard Brook ; Northern hardwood ecosystem ; Photosynthesis ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf surface conductance and apparent photosynthesis were measured during late summer and autumn on saplings and sprouts of pin cherry (Prunus pensylvanica), yellow birch (Betula alleghaniensis), American beech (Fagus grandifolia), and sugar maple (Acer saccharum) naturally revegetating a site in the northern hardwood forest 5 years following a commercial whole-tree harvest. Prior to the disturbance (i.e., the harvest) the site was codominated by American beech, sugar maple, and yellow birch, whereas after the disturbance pin cherry was the dominant species. Conductance and photosynthetic rate of pin cherry leaves were comparatively high while those of American beech and sugar maple were low. Pin cherry retained green, physiologically active leaves longer into autumn than American beech and sugar maple. The rates and seasonal duration of leaf gas exchange on the disturbed site were therefore greater than they would have been had the site not become dominated by pin cherry.
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    Genetic variation in and covariation between leaf gas exchange, morphology, and development in Polygonum arenastrum, an annual plant (1990)
    Springer
    Oecologia 85 (1990), S. 153-158 
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    ISSN: 1432-1939
    Keywords: Polygonum arenastrum ; Photosynthesis ; Water-use efficiency ; Development ; Morphology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We present evidence of genetic variation in and covariation between leaf-level gas exchange properties and leaf size among family lines of Polygonum arenastrum. This self-fertilizing annual had previously been shown to vary genetically in developmental phenology and in morphology (size of leaves, internodes, flowers and seeds) (Geber 1990). Significant family differences were found in photosynthetic carbon assimilation rate (A), lcaf conductance to water vapor (g), instantaneous water-use efficiency (WUE), and leaf carbon isotope discrimination (Δ). A strong positive genetic correlation between A and g suggested that there was stomatal limitation on A. In addition, higher g led to relatively greater increases in transpiration, E, than in assimilation, A, so that families with high rates of gas exchange had lower instantaneous WUE and/or higher carbon isotope discrimination values. Leaf size and gas exchange were genetically correlated. In earlier studies leaf size was found to be genetically correlated with developmental phenology (Geber 1990). The pattern that emerges is one in which small-leaved families (which also have small internodes, flowers, and seeds) tend to have high gas exchange rates, low WUE, rapid development to flowering and high early fecundity, but reduced life span and maximum (vegetative and reproductive) yield compared to large-leaved families. We suggest that this pattern may have arisen from selection for contrasting suites of characters adapted to environments differing in season length.
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    URL: http://dx.doi.org/10.1007/BF00319396
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    Photosynthesis and water-use efficiency in pinyon-juniper communities along an elevation gradient in northern New Mexico (1993)
    Springer
    Oecologia 94 (1993), S. 95-101 
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    ISSN: 1432-1939
    Keywords: δ13C ; Nutrient-use efficiency ; Photosynthesis ; Pinyon-juniper ; Water-use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated plant ecophysiological response to fertilization of selected sites along an elevation gradient in a pinyon-juniper woodland. Plant density and species composition followed typical patterns for pinyon-juniper woodlands over this gradient, with a sparse juniper (Juniperus monosperma (Engelm.) Sarg.)-grassland community at the lowest elevation and gradually increasing total canopy cover and pinyon (Pinus edulis Engelm.) cover with elevation. Carbon isotope analysis showed that both tree species had higher water-use efficiency (WUE) at the lowest, and presumably driest, sites. Over most of the gradient, however, it appeared that changes in stand density compensated for changes in water availability. Contrary to initial hypotheses, the more drought-tolerant juniper did not demonstrate significantly greater WUE than pinyon, although it maintained positive carbon gain at lower predawn xylem pressure potentials than pinyon. In pinyon, both A max and WUE increased with increasing N concentration in tissues. Pinyon needles also demonstrated declining nitrogen-use efficiency with age. There was no relationship between tissue N and either A max or WUE measured at A max in juniper, although δ13C analysis indicated that WUE increased in juniper with increased N availability. Results from this study suggest that plasticity in plant physiological processes could result in nonlinear responses of organic matter production to climate change, and therefore must be accounted for in ecosystem models.
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    Photosynthesis in willows (Salix × dasyclados) grown at different CO2 concentrations and fertilization levels (1992)
    Springer
    Oecologia 91 (1992), S. 208-213 
    Details
    ISSN: 1432-1939
    Keywords: Photosynthesis ; CO2 concentration ; Nutrient status ; Light intensity ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Willows (Salix x dasyclados) were grown for 4 months in growth chambers at four nutrient and CO2 levels, and photosynthesis measurements were made during the latter half of this period. Photosynthesis became saturated at lower light intensities at low CO2 concentrations than at higher ones. The effect of CO2 concentration on photosynthesis was greater at higher temperatures. The willows grown at the highest CO2 concentration (1000 ppm) had a lower photosynthetic capacity than the others when measured at various concentrations. The effect of nutrient status on photosynthesis clearly increased with rising CO2 concentrations. Although photosynthetic acclimation took place to a certain extent at higher CO2 concentrations, photosynthesis still remained higher the higher the growth concentration was. At each CO2 level photosynthesis increased contemporaneously with leaf nitrogen content, but at each fertilization level a rise in CO2 concentration slightly increased photosynthesis and reduced the nitrogen content. The relative increase in photosynthesis achieved by a rise in CO2 was greater than the corresponding increase in biomass growth, whereas the effect of fertilization was greater on biomass growth than on the rate of photosynthesis in the same willows.
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    URL: http://dx.doi.org/10.1007/BF00317785
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    Gas exchange characteristics and nitrogen relations of two Mediterranean root hemiparasites:Bartsia trixago andParentucellia viscosa (1993)
    Springer
    Oecologia 95 (1993), S. 145-151 
    Details
    ISSN: 1432-1939
    Keywords: Photosynthesis ; Nitrogen ; Parasitic angiosperm ; Gas exchange ; Leaf conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plant height, light-saturated rates of photosynthesis (A max) and foliar nitrogen concentration (N 1) were measured forBartsia trixago under field conditions in Mallorca. All three variables were postively correlated, and were also positively related to the abundance of nitrogen-fixing legumes in the associated vegetation (putative host species).A max forB. trixago ranged from 7.7 to 18.8 μmol m-2 s-1; similar rates were measured for a second hemiparasiteParentucellia viscosa, and both species were within the range of rates measured for six putative hosts (10.6–19.2 μmol m-2 s-1). Fertilization of unattachedB. trixago plants with inorganic nitrogen (ammonium nitrate) elicited neither the growth nor the photosynthetic responses observed in plants considered to be parasitic on legumes and in receipt of an enriched organic nitrogen supply. Both hemiparasites had high diurnal leaf conductances (g s) (469–2291 mmol m-2 s-1) and were at the upper end of the range of those measured in putative hosts (409–879 mmol m-2 s-1). In contrast with the latter, high nocturnal rates ofg s were also recorded for the two hemiparasites (517–1862 mmol m-2 s-1). There was no clear relationship between eitherA max orN 1 and eitherg s, transpiration (E) or water use efficiency (A max/E) inB. trixago plants. The economics of water loss appear to be independent of both the supply of nitrogen from the host and autotrophic carbon fixation.
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    URL: http://dx.doi.org/10.1007/BF00649518
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    Photosynthetic characteristics of a giant alpine plant, Rheum nobile Hook. f. et Thoms. and of some other alpine species measured at 4300 m, in the Eastern Himalaya, Nepal (1993)
    Springer
    Oecologia 95 (1993), S. 194-201 
    Details
    ISSN: 1432-1939
    Keywords: Alpine plants ; Himalaya ; Monsoon ; Nitrogen ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The photosynthetic characteristics of a giant alpine plant, Rheum nobile Hook. f. et Thoms. and of some other alpine species were studied in situ at 4300 m, in the Eastern Himalaya, Nepal, during the summer monsoon season. Although rainy and overcast weather was predominant, the daytime photon flux density (400–700 nm) ranged from 300 to 500 μmol quanta m-2 s-1. Under such conditions, the temperature of leaves of R. nobile ranged from 10 to 14°C, and the rate of photosynthetic CO2 exchange ranged from 10 to 16 μmol CO2 m-2 s-1. The ratios of the maximum rate of photosynthetic CO2 fixation to leaf nitrogen content (defined as instantaneous nitrogen-use efficiency, NUE) for the Himalayan forbs that were examined in situ were similar to the NUE values reported for lowland herbaceous species examined under lowland conditions. In contrast to the common belief, theoretical calculations indicate that the decrease in the rate of photosynthesis due to low atmospheric pressure is small. These Himalayan forbs appeared to overcome this small disadvantage by increasing stomatal conductance. Suppression of photosynthesis caused by blockage of stomata by raindrops appeared to be avoided by either of two mechanisms: plants had large hypostomatous leaves that expanded horizontally or they had obliquely oriented amphistomatous leaves without bundle sheath extensions. All these observations indicate that the gas-exchange characteristics of alpine forbs in the Eastern Himalaya are adapted to the local wet and humid monsoon conditions and thus photosynthetic rates attained during the monsoon period are similar to those of lowland plants.
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    URL: http://dx.doi.org/10.1007/BF00323490
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    Photosynthetic and structural acclimation to light direction in vertical leaves of Silphium terebinthinaceum (1993)
    Springer
    Oecologia 95 (1993), S. 393-400 
    Details
    ISSN: 1432-1939
    Keywords: Functional symmetry ; Leaf anatomy ; Leaf orientation ; Light environment ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The azimuth of vertical leaves of Silphium terebinthinaceum profoundly influenced total daily irradiance as well as the proportion of direct versus diffuse light incident on the adaxial and abaxial leaf surface. These differences caused structural and physiological adjustments in leaves that affected photosynthetic performance. Leaves with the adaxial surface facing East received equal daily integrated irradiance on each surface, and these leaves had similar photosynthetic rates when irradiated on either the adaxial or abaxial surface. The adaxial surface of East-facing leaves was also the only surface to receive more direct than diffuse irradiance and this was the only leaf side which had a clearly defined columnar palisade layer. A potential cost of constructing East-facing leaves with symmetrical photosynthetic capcity was a 25% higher specific leaf mass and increased leaf thickness in comparison to asymmetrical South-facing leaves. The adaxial surface of South-facing leaves received approximately three times more daily integrated irradiance than the abaxial surface. When measured at saturating CO2 and irradiance, these leaves had 42% higher photosynthetic rates when irradiated on the adaxial surface than when irradiated on the abaxial surface. However, there was no difference in photosynthesis for these leaves when irradiated on either surface when measurements were made at ambient CO2. Stomatal distribution (mean adaxial/abaxial stomatal density = 0.61) was unaffected by leaf orientation. Thus, the potential for high photosynthetic rates of adaxial palisade cells in South-facing leaves at ambient CO2 concentrations may have been constrained by stomatal limitations to gas exchange. The distribution of soluble protein and chlorophyll within leaves suggests that palisade and spongy mesophyll cells acclimated to their local light environment. The protein/chlorophyll ratio was high in the palisade layers and decreased in the spongy mesophyll cells, presumably corresponding to the attentuation of light as it penetrates leaves. Unlike some species, the chlorophyll a/b ratio and the degree of thylakoid stacking was uniform throughout the thickness of the leaf. It appears that sun-shade acclimation among cell layers of Silphium terebinthinaceum leaves is accomplished without adjustment to the chlorophyll a/b ratio or to thylakoid membrane structure.
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    URL: http://dx.doi.org/10.1007/BF00320994
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    Importance of the gradient in photosynthetically active radiation in a vegetation stand for leaf nitrogen allocation in two monocotyledons (1993)
    Springer
    Oecologia 95 (1993), S. 416-424 
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    ISSN: 1432-1939
    Keywords: Brachypodium pinnatum ; Carex acutiformis ; Nitrogen allocation ; Photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carex acutiformis and Brachypodium pinnatum were grown with a uniform distribution of photosynthetic photon flux density (PFD) with height, and in a vertical PFD gradient similar to the PFD gradient in a leaf canopy. Distribution of organic leaf N and light-saturated rates of photosynthesis were determined. These parameters were also determined on plants growing in a natural vegetation stand. The effect of a PFD gradient was compared with the effect of a leaf canopy. In Brachypodium, plants growing in a vegetation stand had increasing leaf N with plant height. However, distribution of leaf N was not influenced by the PFD gradient treatment. The gradient of leaf N in plants growing in a leaf canopy was not due to differences within the long, mostly erect, leaves but to differences between leaves. In Carex, however, the PFD gradient caused a clear increase of leaf N with height in individual leaves and thus also in plants. The leaf N gradient was similar to that of plants growing in a leaf canopy. Leaf N distribution was not affected by nutrient availability in Carex. In most cases, photosynthesis was positively related to leaf N. Hence, lightsaturated rates of photosynthesis increased towards the top of the plants growing in leaf canopies in both species and, in Carex, also in the PFD gradient, thus contributing to increased N use efficiency for photosynthesis of the whole plant. It is concluded that in Carex the PFD gradient is the main environmental signal for leaf N allocation in response to shading in a leaf canopy, but one or more other signals must be involved in Brachypodium.
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    URL: http://dx.doi.org/10.1007/BF00320997
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    Increased photosynthesis and water potentials in Silphium integrifolium galled by cynipid wasps (1993)
    Springer
    Oecologia 93 (1993), S. 114-120 
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    ISSN: 1432-1939
    Keywords: Photosynthesis ; Water potential ; Gall insect ; Silphium integrifolium ; Plant-insect interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Interactions between drought, insect herbivory, photosynthesis, and water potential play a key role in determining how plants tolerate and defend against herbivory, yet the effects of insect herbivores on photosynthesis and water potential are seldom assessed. We present evidence that cynipid wasp galls formed by Antistrophus silphii on Silphium integrifolium increase photosynthesis (A), stomatal conductance (g), and xylem water potential (Ψ). Preliminary data showed that in drought-stressed plants galled shoots had 36% greater A, and 10% greater stem Ψ than ungalled shoots, while in well-watered plants leaf gas exchange was not affected by galls. We hypothesized that 1) galled shoots have higher Ψ, g, and A than ungalled shoots, but this differences diminishes if plant drought stress is reduced, and 2) galls can reduce decreases in A and g if water availability decreases. A field experiment testing the first hypothesis found that galls increased g and Ψ, but that differences between galled and ungalled shoots did not diminish after plants were heavily watered. A laboratory test of the second hypothesis using potted Silphium found that galled plants had smaller drops in A and g over a 4-day dry-down period. A vs g and A vs intercellular CO2 concentration relationships were consistent with the explanation that increased Ψ allows galls to increase A by reducing stomatal limitation of A, rather than by altering sink-source relationships or by removing low-Ψ limitations on non-stomatal components of A. Our working hypothesis is that galls increase Ψ and A by reducing the shoot: root ratio so that the plant is exploiting a greater soil volume per unit leaf area. We argue that increased A is an ineffective way for Silphium to compensate for negative effects of gall insect attack. Instead, increased Ψ and A may protect gall insects from variation in resource availability caused by periodic drought stress, potentially reducing negative effects of drought on plant quality and on gall insect populations.
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    URL: http://dx.doi.org/10.1007/BF00321200
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    Photosynthetic induction times in shade-tolerant species with long and short-lived leaves (1993)
    Springer
    Oecologia 93 (1993), S. 165-170 
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    ISSN: 1432-1939
    Keywords: Photosynthesis ; Induction ; Light flecks ; Leaf lifespan ; Rainforest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In the understory of a tropical rainforest, light flecks can contribute 10–80% of the total light flux. We investigated the capacity of eight shade-tolerant species to use light flecks by examining the time required for full induction of photosynthesis during an artificial light fleck. CO2 fixation rates were measured with a portable LiCor gas-exchange system for plants growing in the field on Barro Colorado Island, Panama. In all species induction to 50% of maximum CO2 fixation occurred quickly, from 1 to 3 min. In species with short leaf lifetimes (1 year), induction to 90% of maximum also occurred quickly, in 3–6 min. In contrast, the species with longer lived leaves (〉4 years) required 11–36 min for induction to 90% of maximum. Induction times for leaves from gap and understory plants of the same species were indistinguishable. Elevated CO2 did not eliminate the slow induction phase of long-lived leaves. This suggests that slow induction did not result from stomatal limitation. O2 evolution, measured on excised leaf disks, induced in 3–4 min in species with short-lived leaves, and 4–8 min in species with long-lived leaves. The rapid induction of O2 evolution indicates that the slower induction of CO2 fixation in long-lived leaves was not caused by a delay in the induction of electron transport. Activation of rubisco may be the major factor limiting response times in species with long-lived leaves. Species from Panama with short-lived leaves had remarkably rapid induction times that are comparable to those of algae or higher plant chloroplasts. We also found that understory forest plants induced two to seven times more quickly than did potted plants.
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    URL: http://dx.doi.org/10.1007/BF00317666
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    Photosynthesis-nitrogen relations in Amazonian tree species (1994)
    Springer
    Oecologia 97 (1994), S. 73-81 
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    ISSN: 1432-1939
    Keywords: Specific leaf area ; Rain forests ; Photosynthesis ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationships between leaf nitrogen (N), specific leaf area (SLA) (an inverse index of leaf “thickness” or “density”), and photosynthetic capacity (Amax) were studied in 23 Amazonian tree species to characterize scaling in these properties among natural populations of leaves of different ages and light microenvironments, and to examine how variation within species in N and SLA can influence the expression of the Amax-to-N relationship on mass versus area bases. The slope of the Amax-N relationship, change in A per change in N (μmol CO2 gN-1 s-1), was consistently greater, by as much as 300%, when both measures were expressed on mass rather than area bases. The x-intercept of this relationship (N-compensation point) was generally positive on a mass but not an area basis. In this paper we address the causes and implications of such differences. Significant linear relationships (p〈0.05) between mass-based leaf N (Nmass) and SLA were observed in 12 species and all 23 regressions had positive slopes. In 13 species, mass-based Amax (Amass) was positively related (p〈0.05) with SLA. These patterns reflect the concurrent decline in Nmass and SLA with increasing leaf age. Significant (p〈0.05) relationships between area-based leaf N (Narea) and SLA were observed in 18 species. In this case, all relationships had negative slopes. Taken collectively, and consistent in all species, as SLA decreased (leaves become “thicker”) across increasing leaf age and light gradients, Nmass also decreased, but proportionally more slowly, such that Narea increased. Due to the linear dependence of Amass on Nmass and a negative 4-intercept, “thicker” leaves (low SLA) therefore tend, on average, to have lower Nmass and Amass but higher Narea than “thinner” leaves. This tendency towards decreasing Amass with increasing Narea, resulting in a lower slope of the Amax-N relationship on an area than mass basis in 16 of 17 species where both were significant. For the sole species exception (higher area than mass-based slope) variation in Narea was related to variation in Nmass and not in SLA, and thus, these data are also consistent with this explanation. The relations between N, SLA and Amax explain how the rate of change in Amax per change in N can vary three-fold depending on whether a mass or area mode of expression is used.
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    URL: http://dx.doi.org/10.1007/BF00317910
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    Relationship of aluminium and calcium to net CO2 exchange among diverse Scots pine provenances under pollution stress in Poland (1994)
    Springer
    Oecologia 97 (1994), S. 82-92 
    Details
    ISSN: 1432-1939
    Keywords: Photosynthesis ; Respiration ; Pinus sylvestris ; Pinus nigra ; Betula pubescens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Light-saturated net photosynthesis (Asat), dark respiration (RD), and foliar nutrient content of eight European Scots pine (Pinus sylvestris L.) provenances were measured at experimental sites in western Poland. Two-year-old seedlings were planted in 1984 at two sites with similar soils in areas of contrasting air pollution. One site was near a point source of SO2 and other pollutants, and another 12 km to the southeast in an area free of acute air pollution was treated as a control. The eight provenances were from a large north-tosouth latitudinal range (60 to 43° N). At the heavily polluted site Scots pine trees exhibited lower growth rates and crown dieback and deformation. Soil pH, Ca and Mg were at least 10 times lower, and Al 10 times higher at the polluted than the control site. In 1991, concentrations of Al, P, Ca, S, Mn, Fe, and Zn in oneyear old Scots pine foliage were higher and Mg lower at the polluted than control site. At both sites foliar Mg levels were within the range considered deficient (≤0.6 mg g-1), and at the polluted site, Al concentrations were very high (670 to 880 μg g-1). In all provenances, RD of one-year-old needles was higher (by 22% on average) and Asat was lower (by 37% on average) at the polluted than the control site. The ratio of Asat: RD was half as great in all provenances at the polluted (4 to 6) than control site (8 to 11). Provenances of southern origin had greater increases in RD and water-use efficiency at the polluted site than other provenances. Within the polluted site alone, or across both sites, Asat in Scots pine was negatively correlated to the Al: Ca ratio (p〈0.001, r=−0.93). Across sites RD increased with needle N and Al (multiple regression, p〈0.001). The data suggest that at the polluted site there is excessive soil Al and deficient Mg availability, low needle Mg and high Al concentrations and high Al: Ca ratios, and that these have resulted in reduced photosynthetic capacity and increased respiration.
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    URL: http://dx.doi.org/10.1007/BF00317911
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    Photosynthesis-nitrogen relations in Amazonian tree species (1994)
    Springer
    Oecologia 97 (1994), S. 62-72 
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    ISSN: 1432-1939
    Keywords: Amazon ; Rain forests ; Leaf life-span ; Photosynthesis ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Among species, photosynthetic capacity (Amax) is usually related to leaf nitrogen content (N), but variation in the species-specific relationship is not well understood. To address this issue, we studied Amax-N relationships in 23 species in adjacent Amazonian communities differentially limited by nitrogen (N), phosphorus (P), and/or other mineral nutrients. Five species were studied in each of three late successional forest types (Tierra Firme, Caatinga and Bana) and eight species were studied on disturbed sites (cultivated and early secondary successional Tierra Firme plots). Amax expressed on a mass basis (Amass) was correlated (p〈0.05) with Nmass in 17 of 23 species, and Amax on an area basis (Aarea) was correlated (p〈0.05) with Narea in 21 of 23 species. The slopes of Amax-N relationships were greater and intercepts lower for disturbance adapted early successional species than for late successional species. On a mass basis, the Amax-N slope averaged ≈15 μmol CO2 [g N]-1 s-1 for 7 early secondary successional species and ≈4 μmol CO2 [g N]-1 s-1 for 15 late successional species, respectively. Species from disturbed sites had shorter leaf life-span and greater specific leaf area (SLA) than late successional species. Across all 23 species, the slope of the Amass-Nmass relationship was related (p〈0.001) positively to SLA (r2=0.70) and negatively to leaf life-span (r2=0.78) and temporal niche during secondary succession (years since cutting-and-burning, r2=0.90). Thus, disturbance adapted early successional species display a set of traits (short leaf life-span, high SLA and Amax and a steep slope of Amax-N) conducive to resource acquisition and rapid growth in their high resource regeneration niches. The significance and form of the Amax-N relationship were associated with the relative nutrient limitations in the three late successional communities. At species and community levels, Amax was more highly dependent on N in the N-limited Caatinga than in the P-and N-limited Bana and least in the P-and Ca-limited Tierra Firme on oxisol-and differences among these three communities in their massbased Amax-N slope reflects this pattern (6.0, 2.4, and 0.7 μmol CO2 [g N]-1 s-1, respectively). Among all 23 species, the estimated leaf Nmass needed to reach compensation (net photosynthesis ≈ zero) was positively related to the Amass-Nmass slope and to dark respiration rates and negatively related to leaf life-span. Variation among species in the Amax-N slope was well correlated with potential photosynthetic N use efficiency, Amax per unit leaf N. The dependence of Amax on N and the form of the relationship vary among Amazonian species and communities, consistent with both relative availabilities of N, P, and other mineral nutrients, and with intrinsic ecophysiological characteristics of species adapted to habitats of varying resource availability.
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    Shoot growth dynamics and photosynthetic response to increased nitrogen availability in the alpine willow Salix glauca (1994)
    Springer
    Oecologia 97 (1994), S. 93-99 
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    ISSN: 1432-1939
    Keywords: Alpine ecosystem ; Biomass allocation ; Nitrogen-use efficiency ; Photosynthesis ; Salix glauca
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants subjected to increases in the supply of resource(s) limiting growth may allocate more of those resources to existing leaves, increasing photosynthetic capacity, and/or to production of more leaves, increasing whole-plant photosynthesis. The responses of three populations of the alpine willow, Salix glauca, growing along an alpine topographic sequence representing a gradient in soil moisture and organic matter, and thus potential N supply, to N amendments, were measured over two growing seasons, to elucidate patterns of leaf versus shoot photosynthetic responses. Leaf-(foliar N, photosynthesis rates, photosynthetic N-use efficiency) and shoot-(leaf area per shoot, number of leaves per shoot, stem weight, N resorption efficiency) level measurements were made to examine the spatial and temporal variation in these potential responses to increased N availability. The predominant response of the willows to N fertilization was at the shoot-level, by production of greater leaf area per shoot. Greater leaf area occurred due to production of larger leaves in both years of the experiment and to production of more leaves during the second year of fertilization treatment. Significant leaflevel photosynthetic response occurred only during the first year of treatment, and only in the dry meadow population. Variation in photosynthesis rates was related more to variation in stomatal conductance than to foliar N concentration. Stomatal conductance in turn was significantly related to N fertilization. Differences among the populations in photosynthesis, foliar N, leaf production, and responses to N fertilization indicate N availability may be lowest in the dry meadow population, and highest in the ridge population. This result is contrary to the hypothesis that a gradient of plant available N corresponds with a snowpack/topographic gradient.
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    Morning vs afternoon sun patches in experimental forest gaps: consequences of temporal incongruency of resources to birch regeneration (1993)
    Springer
    Oecologia 94 (1993), S. 235-243 
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    ISSN: 1432-1939
    Keywords: Betula ; Photosynthesis ; Seedling regeneration ; Timing of resource availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated whether the timing of high light availability as sun patches within forest gaps, independent of total or peak photosynthetic photon flux (PPF), influences the physiology and growth of four coexisting birch species (Betula alleghaniensis, B. lenta, B. papyrifera, and B. populifolia). Birch seedlings were grown for two years along either the east or west sides of experimental gap structures and at two moisture levels. Seedlings positioned in the west received sun patches earlier in the day than those in the east, and environmental conditions for carbon gain were generally more favorable during the earlier sunpatches in the west; air and leaf temperatures were lower, and relative humidity higher, relative to conditions during sun patches in the cats, simulating patterns observed in natural forest gaps. Seedlings positioned along the west edges of gaps fixed more carbon earlier in the day than those in the east, and in many cases, peak net photosynthetic rates were greater for west positioned seedlings. In year two, leaf-level integrated daily carbon gain was greater for west- than eastpositioned plants, and for the most pioneer species, B. populifolia, differences between west and east seedlings were greatest at lower soil moisture levels. Despite some small effects on leaf gas exchange, the timing of high light availability, and its temporal congruence with other factors critical to carbon gain, had no significant effects on first or second year seedling biomass. The responses of birch seedlings to controlled variations in the timing of high light availability were generally much smaller than birch seedling responses to variations in other components of daily light regimes such as total integrated and peak PPF.
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    URL: http://dx.doi.org/10.1007/BF00341322
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    Performance of two Picea abies (L.) Karst. stands at different stages of decline (1990)
    Springer
    Oecologia 82 (1990), S. 158-161 
    Details
    ISSN: 1432-1939
    Keywords: Air pollution ; Acid rain ; Photosynthesis ; Nutrition ; Picea abies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Photosynthetic rates and nutrient contents of spruce needles were measured in a region with high levels of air pollution in NE Bavaria, Germany (FRG), and compared to spruce grown under clean air conditions at Craigieburn, in the South Island of New Zealand (NZ). The absolute rates of CO2 uptake, the slope of the CO2 response curve at 240 μl l−1 internal CO2 concentration, and the change of photosynthetic rates with needle age at ambient and saturated CO2 concentrations were virtually identical at both measuring sites. These results confirm an earlier conclusion, that there is no long-term effect of atmospheric pollutants directly on photosynthetic CO2 uptake rates with persistent exposure at the FRG site to high levels of anthropogenic air pollution. Photosynthetic capacity at saturating CO2 concentration was three times higher in the NZ spruce. Needles with high photosynthetic capacity in NZ had lower nitrogen and higher calcium concentrations per unit dry weight but higher concentrations of nitrogen, phosphorus, potassium, magnesium and calcium per unit leaf area, and twice the specific leaf weight.
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    Factors influencing carbon fixation and water use by mediterranean sclerophyll shrubs during summer drought (1990)
    Springer
    Oecologia 82 (1990), S. 381-393 
    Details
    ISSN: 1432-1939
    Keywords: Photosynthesis ; Stomata ; Model ; Rootshoot interaction ; Sclerophyllous plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mediterranean sclerophyll shrubs respond to seasonal drought by adjusting the amount of leaf area exposed and by reducing gas exchange via stomatal closure mechanisms. The degree to which each of these modifications can influence plant carbon and water balances under typical mediterranean-type climate conditions is examined. Leaf area changes are assessed in the context of a canopy structure and light microclimate model. Shifts in physiological response are examined with a mechanistically-based model of C3 leaf gas exchange that simulates progressive reduction of maximum photosynthesis and transpiration rates and increasingly strong midday stomatal closure over the course of drought. The results demonstrate that midday stomatal closure may effectively contribute to drought avoidance, increase water use efficiency, and strongly alter physiological efficiency in the conversion of intercepted light energy to photoproducts. Physiological adjustments lead to larger reductions in water use than occur when comparing leaf area index 3.5 to 1.5, extremes found for natural stands of sclerophyll shrubs in the California chaparral. Reductions in leaf area have the strongest effect on resource capture and use during non-water-stressed periods and the least effect under extreme drought conditions, while shifts in physiological response lead to large savings of water and efficient water use under extreme stress. An important model parameter termed GFAC (proportionality factor expressing the relation of conductance [g] to net photosynthesis rate) is utilized, which changes in response to the integrated water stress experimence of shrubs and alters the degree to which stomata may open for a given rate of carbon fixation. We attempt to interpret this parameter in terms of physiological mechanisms known to modify control of leaf gas exchange during drought. The analysis helps visualize means by which canopy gas exchange behavior may be coupled to physiological changes occurring in the root environment during soil drying.
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    Leaf lifespan as a determinant of leaf structure and function among 23 amazonian tree species (1991)
    Springer
    Oecologia 86 (1991), S. 16-24 
    Details
    ISSN: 1432-1939
    Keywords: Leaf lifespan ; Amazon ; Photosynthesis ; Specific leaf area ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The relationships between resource availability, plant succession, and species' life history traits are often considered key to understanding variation among species and communities. Leaf lifespan is one trait important in this regard. We observed that leaf lifespan varies 30-fold among 23 species from natural and disturbed communities within a 1-km radius in the northern Amazon basin, near San Carlos de Rio Negro, Venezuela. Moreover, leaf lifespan was highly correlated with a number of important leaf structural and functional characterisues. Stomatal conductance to water vapor (g) and both mass and area-based net photosynthesis decreased with increasing leaf lifespan (r2=0.74, 0.91 and 0.75, respectively). Specific leaf area (SLA) also decreased with increasing leaf lifespan (r2=0.78), while leaf toughness increased (r2=0.62). Correlations between leaf lifespan and leaf nitrogen and phosphorus concentrations were moderate on a weight basis and not significant on an area basis. On an absolute basis, changes in SLA, net photosynthesis and leaf chemistry were large as leaf lifespan varied from 1.5 to 12 months, but such changes were small as leaf lifespan increased from 1 to 5 years. Mass-based net photosynthesis (A/mass) was highly correlated with SLA (r2=0.90) and mass-based leaf nitrogen (N/mass) (r2=0.85), but area-based net photosynthesis (A/area) was not well correlated with any index of leaf structure or chemistry including N/area. Overall, these results indicate that species allocate resources towards a high photosynthetic assimilation rate for a brief time, or provide resistant physical structure that results in a lower rate of carbon assimilation over a longer time, but not both.
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    URL: http://dx.doi.org/10.1007/BF00317383
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  • 89
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    Influence of sunflecks on the δ 13 C of Adenocaulon bicolor plants occurring in contrasting forest understory microsites (1991)
    Springer
    Oecologia 86 (1991), S. 457-462 
    Details
    ISSN: 1432-1939
    Keywords: Carbon isotopes ; Photosynthesis ; Gas exchange ; Sun/shade adaptation ; Stomatal conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaf characteristics and carbon isotope ratios (δ13C) of Adenocaulon bicolor were examined in the understory of a redwood forest along a gradient of microsites that differed in the amount of direct (sunfleck) photon flux density. Comparisons were made between plants that had been shaded from sunflecks with shadow bands but still received diffuse light, and adjacent plants that received both sunflecks and diffuse light. The δ13C of the shaded plants were 1.2‰ lower than predicted from the intercellular CO2 pressure (pi), probably because of recycling of respired CO2 in the understory. Plants receiving sunflecks had higher δ13C values because assimilation during sunflecks occurred at a lower pi than assimilation in diffuse light. The amount that their δ13C was higher was positively correlated with predicted direct photon flux density received by a plant. Leaf weight per unit area increased with increasing PFD. Although plants receiving sunflecks had greater leaf weights per unit area and photosynthetic capacities than those under shadow bands, there was no apparent acclimation of photosynthetic capacity to the differences in PFD among the microsites.
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    URL: http://dx.doi.org/10.1007/BF00318310
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  • 90
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    The carboxylase activity of Rubisco and the photosynthetic performance in aquatic plants (1991)
    Springer
    Oecologia 87 (1991), S. 429-434 
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    ISSN: 1432-1939
    Keywords: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) ; Photosynthesis ; Macrophytes ; Aquatic ; Marine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Activated carboxylase activities of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), as well as photosynthetic rates were measured for 42 species of freshwater and marine macrophytes. While the carboxylase activity varied greatly among the species investigated (0.2–12.5 μmol CO2 mg−1 chlorophyll min−1), the submersed freshwater plants showed significantly lower activities than emergent, floating leaved or secondary submersed forms. The variability in photosynthetic rates correlated with the carboxylase activity only for the marine macroalgae, and their photosynthesis to carboxylase activity ratios were close to 1. These plants also had a consistently high inorganic carbon transport capability, and it is suggested that ribulose-1,5-bisphosphate carboxylase/oxygenase activity is an important internal factor regulating the photosynthetic capacity within this plant group where, apparently, the internal CO2 concentration is high and photorespiration is suppressed. Among the freshwater forms, it appears that their much lower inorganic carbon transport ability, rather than their carboxylase activity, limits the photosynthetic process.
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    URL: http://dx.doi.org/10.1007/BF00634602
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  • 91
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    Effects of scale insect herbivory and shading on net gas exchange and growth of a subtropical tree species (Guaiacum sanctum L.) (1990)
    Springer
    Oecologia 84 (1990), S. 468-473 
    Details
    ISSN: 1432-1939
    Keywords: Toumeyella sp. ; Insect-plant interaction ; Photosynthesis ; Chlorophyll ; Nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The scale insect, Toumeyella sp., feeds exclusively on the subtropical hammock tree lignum vitae (Guaiacum sanctum L.). The combined effects of scale herbivory and shading on leaf gas exchange characteristics and growth of lignum vitae trees were studied using a factorial design. Trees grown in full sun or in 75% shade were manually infested with scale or left noninfested. Beginning 4 weeks after infestation, net CO2 assimilation, stomatal conductance, transpiration, internal partial pressure of CO2, and water-use efficiency were determined on single-leaves at 4-week intervals for trees in each treatment. At the end of the experiment, net CO2 assimilation was determined for whole plants. Total leaf area, leaf, stem, and root dry weights, and leaf chlorophyll and nitrogen concentrations were also determined. Scale infested trees generally had lower net CO2 assimilation, stomatal conductance, and transpiration rates as well as less leaf area, and root, stem, and leaf dry weights than noninfested trees. Twenty four weeks after the shade treatment was imposed, sun-grown trees had approximately twice the leaf area of shade-grown trees. Shade-grown trees compensated for the reduced leaf area by increasing their photosynthetic efficiency. This resulted in no difference in light saturated net CO2 assimilation on a whole plant basis between sun-grown and shade-grown trees. Chlorophyll and nitrogen concentrations per unit leaf area were greater in leaves of shade-grown trees than in leaves of sun-grown trees. Shading and herbivory by Toumeyella sp. each resulted in decreased growth of Guaiacum sanctum. Scale insect herbivory did not result in greater detrimental effects on leaf gas exchange characteristics for shade-grown than for sun-grown trees. Herbivory by Toumeyella resulted in a greater decrease in tree growth for sun-grown than for shade-grown trees.
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    URL: http://dx.doi.org/10.1007/BF00328162
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  • 92
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    Effect of soil temperature on stem sap flow, shoot gas exchange and water potential of Picea engelmannii (Parry) during snowmelt (1990)
    Springer
    Oecologia 84 (1990), S. 474-481 
    Details
    ISSN: 1432-1939
    Keywords: Diurnal ; Shoot conductance ; Photosynthesis ; Root ; Stem capacitance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The effect of cold soils on stem sap flow, shoot gas exchange and water potential of Picea engelmannii (Parry) was investigated during the snowmelt period in the Medicine Bow Mountains, Wyoming, USA. Shoot net photosynthetic rates were higher in young trees (1.5–1.8 m in height) growing in cold soils (〈3.5° C) associated with snowpack, than trees in warm soils until about 1500 h. Higher shoot photosynthetic rates of trees in cold soils continued after snow was removed and could not be completely explained by higher visible irradiance over highly reflective snow. Following soil warming higher photosynthetic rates were evident in these trees for five days. High nutrient availability associated with snowmelt may improve shoot nutrient status leading to higher gas-exchange rates during snowmelt. Shoot conductance to water vapor was higher in trees in cold soil until midday, when declining shoot conductance led to lower intercellular CO2 concentrations. Midday through afternoon shoot water potentials of trees in cold soils were similar or higher than those of trees in warm soils and the lower afternoon shoot conductances in cold soils were not the result of lower bulk shoot water potentials. Decline in net photosynthesis of trees in cold soils at 1500 h paralleled increases in intercellular CO2 concentrations, implying a nonstomatal limitation of photosynthesis. This scenario occurred consistently in mid-afternoon following higher morning and midday photosynthesis in cold soils, suggesting a carbohydrate feedback inhibition of photosynthesis. Diurnal patterns in stem sap flow of all trees (cold and warm soils) reflected patterns of shoot conductance, although changes in stem sap flow lagged 1–3 h behind shoot conductance apparently due to stem water storage. Total daily stem sap flow was similar in trees in cold and warm soils, although diel patterns differed. The morning surge and night-time drop in sap flow commenced 1–2 h earlier in trees in cold soils. Overnight stem sap flow was lower in trees in cold soils, possibly due to higher resistance to root water uptake in cold soils, which may explain lower predawn shoot water potentials. However, midday shoot water potentials of trees in cold soils equalled or exceeded those of trees in warm soils. Higher resistance to root water uptake in P. engelmannii in cold soils was apparently overshadowed by transpirational forces and significant shoot water deficits did not develop.
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    URL: http://dx.doi.org/10.1007/BF00328163
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  • 93
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    Diurnal variation and interrelations of ecophysiological parameters in three peatland woody species under different weather and soil moisture conditions (1991)
    Springer
    Oecologia 88 (1991), S. 317-324 
    Details
    ISSN: 1432-1939
    Keywords: Diurnal patterns ; Photosynthesis ; Water relations ; Flooding stress ; Peatlands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The diurnal patterns of twig xylem water potential, net photosynthesis rate, water use efficiency of photosynthesis, and stomatal and mesophyll conductance to CO2 in tamarack, black spruce and swamp birch growing in a natural peatland in central Alberta, Canada, were examined. The relationships of photosynthesis to other ccophysiological parameters were investigated. Data were collected on three days with different weather and soil moisture conditions in the 1988 growing season. Day 1 was clear and warm and the ground water table was 7 cm above the average peat surface. Day 2 was clear and hot. Day 3 was cloudy but warm. On day 2 and day 3, the water tables were in the normal range for that season. Major findings were: 1) Soil flooding depressed photosynthesis in tamarack and black spruce. 2) Swamp birch was better adapted to flooding than tamarack or black spruce. 3) The trees experienced water stress in the afternoons of the two days with lower water table. 4) Changes in photosynthesis of the three species were primarily affected by changes in mesophyll conductance (gm) and the response of photosynthesis to changes in gm was similar for all three species.
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    URL: http://dx.doi.org/10.1007/BF00317573
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  • 94
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    Why some fruits are green when they are ripe: carbon balance in fleshy fruits (1991)
    Springer
    Oecologia 88 (1991), S. 371-377 
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    ISSN: 1432-1939
    Keywords: Fruit color ; Photosynthesis ; Carbon balance, fruit ; Seed dispersal ; Tropical forests
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Fruits that are green upon ripening (“green-ripe”) tend to be dispersed by a limited range of frugivores, whereas those that are brightly colored (“bright-ripe”) are dispersed by a wide range of birds and mammals. Because green fruits are probably less conspicuous than other colors of fruits, their pigmentation cannot be attributed to the attraction of seed dispersers. Instead, we hypothesize that a major benefit of green pigmentation is the ability to photosynthesize when ripe. Photosynthesis by fruits may lower their costs of production, and could result in fruits with greater nutrient reward. We present data on physical, chemical, and photosynthetic characteristics of ripe fleshy fruit of variable colors for 28 plant species at the La Selva Biological Station, Costa Rica. In addition to color and morphological characteristics of pulp and seeds, we report soluble solids content (refractive index), and photosynthetic/respiratory carbon-dioxide balance of ripe fruits. Carbon balance was much more dependent upon ambient light levels in green-ripe fruits than in bright-ripe fruit. In particular, data from light response curves indicated that green-ripe fruits may go into positive carbon balance at high light levels (above 300 μmol/m2/s). Rather than finding a positive relationship between soluble solids content and green fruit, as we predicted based on photosynthetic capacity, our data indicate that greater respiration rates of green-ripe fruits may result in carbon losses at low light levels. Our results were consistent with previously described morphological differences between the two color classes, with green-ripe fruits displaying significantly greater wet pulp mass, wet seed mass, and total fruit mass. Our data suggest that photosynthesis due to the retention of chlorophyll in ripe fleshy fruit may offset respiratory costs for plants with large or otherwise costly fruit, but this advantage should be evident only under high-light conditions.
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    URL: http://dx.doi.org/10.1007/BF00317581
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  • 95
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    Photosynthesis in relation to leaf nitrogen and phosphorus content in Zimbabwean trees (1991)
    Springer
    Oecologia 88 (1991), S. 378-382 
    Details
    ISSN: 1432-1939
    Keywords: Photosynthesis ; Leaf nitrogen ; Leaf phosphorus ; Trees ; Zimbabwe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary CO2 assimilation in relation to light intensity and the relationship between leaf nitrogen and phosphorus concentrations and CO2 assimilation in 14 species of ecologically important Zimbabwean trees were examined. Eight of the species are members of the Fabaceae (Leguminosae). In the majority of Zimbabwean climax woodlands, the dominant trees are non-nodulating members of the sub-family Caesalpinioideae. The species examined have higher light saturation points (〉700 μmol m−2 s−1) than woody species from temperate areas; one species, Acacia nigrescens, did not reach saturation at photon fluxes greater than 1500 μmol m−2 sec−1. Higher leaf nitrogen content was found to correlate positively with higher CO2 assimilation rates (r=0.85; P≦0.0003); there was no correlation between leaf phosphorus content and CO2 uptake rates. There were no significant differences between sites in terms of leaf nitrogen or phosphorus content, but the mean photosynthetic rate at one of the sites (Chizedzi) was lower. Taxa from the nodulating legumes were found to have higher leaf nitrogen contents (309.1±SD 22 mmol m−2) than those of the non-nodulating species (239±33); the lowest nitrogen contents were found in nonleguminous trees (179±42), with the exception of Ziziphus mucronata. This species may form an association with an N2-fixing actinomycete.
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    URL: http://dx.doi.org/10.1007/BF00317582
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  • 96
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    Photosynthetic symmetry of sun and shade leaves of different orientations (1991)
    Springer
    Oecologia 87 (1991), S. 51-57 
    Details
    ISSN: 1432-1939
    Keywords: Leaf anatomy ; Photosynthesis ; Functional symmetry ; Leaf orientation ; Optical properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The photosynthetic responses to light of leaves irradiated on the adaxial or abaxial surfaces, were measured for plants with contrasting leaf orientations. For vertical-leaf species of open habitats (Eryngium yuccifolium and Silphium terebinthinaceum), photosynthetic rates were identical when irradiated on either surface. However, for horizontal-leaf species of open habitats (Ambrosia trifida and Solidago canadensis), light-saturated rates of photosynthesis for adaxial irradiation were 19 to 37% higher than rates for abaxial irradiation. Leaves of understory plants (Asarum canadense and Hydrophyllum canadense) were functionally symmetrical although they had horizontal orientation. Photosynthetic rates were measured at saturating CO2, thus differences in the response to incident irradiance presumably resulted from complex interactions of light and leaf optical properties rather than from stomatal effects. Differences in absorptance (400–700 nm) among leaf surfaces were evident for horizontal-leaf species but the primary determinant of functional symmetry was leaf anatomy. Functionally symmetrical leaves had upper and lower palisade layers of equal thickness (vertical leaves of open habitats) or were composed primarily of a single layer of photosynthetic cells (horizontal leaves of understory habitats). Photosynthetic symmetry of vertical-leaf species may be an adaptation to maximize daily integrated carbon gain and water-use efficiency, whereas asymmetry of horizontal-leaf species may be an adaptation to maximize daily integrated carbon gain and photosynthetic nutrient-use efficiency.
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    URL: http://dx.doi.org/10.1007/BF00323779
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  • 97
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    Carotenoid composition and photon-use efficiency of photosynthesis inGossypium hirsutum L. grown under conditions of slightly suboptimum leaf temperatures and high levels of irradiance (1991)
    Springer
    Oecologia 87 (1991), S. 349-356 
    Details
    ISSN: 1432-1939
    Keywords: Chlorophyll fluorescence ; Cotton ; Photoinhibition ; Photosynthesis ; Xanthophyll cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cotton (Gossypium hirsutum L. var. DP 61) was grown at different temperatures during 12-h light periods, with either 1800–2000 μmol photons m−2 s−1 (high photon flux density, PFD) or 1000–1100 μmol m−2 s−1 (medium PFD) incident on the plants. Night temperature was 25°C in all experiments. Growth was less when leaf temperatures were below 30°C during illumination, the effect being greater in plants grown with high PFD (Winter and Königer 1991). Leaf pigment composition and the photon-use efficiency of photosynthesis were analysed to assess whether plants grown with high PFD and suboptimal temperatures experienced a higher degree of high irradiance stress during development than those grown with medium PFD. The chlorophyll content per unit area was 3–4 times less, and the content of total carotenoids about 2 times less, with the proportion of the three xanthophylls zeaxanthin + antheraxanthin + violaxanthin being greater in leaves grown at 20–21°C than in leaves grown at 33–34°C. In leaves from plants grown at 21°C and 1800–2000 μmol photons m−2 s−1, zeaxanthin accounted for as much as 34% of total carotenoids in the middle of the photoperiod, the highest level recorded in this study. This finding is consistent with a protective role of zeaxanthin under conditions of excess light. At the lower temperatures, the photochemical efficiency of photosystem II, measured as the ratio of variable to maximum fluorescence yield (F V/F M) after 12-h dark adaptation, was 0.76 in medium PFD plants and 0.75 in high PFD plants compared with 0.83 and 0.79, respectively, at the higher temperatures. The photon-use efficiency of O2 evolution (ϕ) based on absorbed light between 630 and 700nm, decreased with decrease in temperature from 0.102 to 0.07 under conditions of high PFD, but remained above 0.1 at medium PFD. Owing to compensatory reactions in these long-term growth experiments, sustained differences inF V/F M and ϕ were much less pronounced than the differences in chlorophyll content and dry matter, particularly in plants which had developed at high PFD and low temperature. In fact, in these plants, which exhibited pronounced photobleaching, a largely functional photosynthetic apparatus was still maintained in cells adjacent to the lower leaf surfaces. This was indicated by measurements of photon use efficiencies of photosynthetic O2 evolution with leaves illuminated first at the upper, and then at the lower surface.
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    URL: http://dx.doi.org/10.1007/BF00634590
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  • 98
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    Is long-lived foliage in Picea mariana an adaptation to nutrient-poor conditions? (1992)
    Springer
    Oecologia 91 (1992), S. 184-191 
    Details
    ISSN: 1432-1939
    Keywords: Foliar nutrient retranslocation ; Needle age ; Photosynthesis ; Nitrogen ; Phosphorus ; Respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study evaluated the contribution of different ages of foliage to the nutrient and carbon balance of black spruce (Picea mariana (Mill.) B.S.P.) from a nutrient-poor peatland in Alberta. Seasonal patterns of foliar nitrogen and phosphorus concentration and content were examined in six needle cohorts up to 10 years old. Trees were treated to simulate excess nutrient deficiency (removal of all one-year-old foliage), nutrient excess (fertilized with 250, 50, 100 kg ha−1 NPK split application in June and July), or left as controls. Gas exchange (net assimilation-Na, stomatal conductance-gs, mesophyll conductance-gm, water-use efficiency-WUE, dark respiration-RS) was measured on six different needle cohorts in several control trees in 1989 and 1990. Nitrogen and phosphorus concentration decreased with needle age. Foliar nutrient concentration fell from April to June and then was stable until September except for the fertilized trees where it increased. There was no evidence of greater than normal retranslocation of nutrients from older needles for defoliated trees or greater than normal nutrient loading in older needles of fertilized trees. NA, gs, gm, WUE, and RS were similar for all needles up to six or eight years old, these older needles having NA of 65% of current needles and similar RS. The results do not support to conclusion that older needles of black spruce are retained as an adaptation to nutrient stress. It does not appear that older needles serve as a nutrient storage site in conditions of excess nutrient availability or a greater than normal nutrient source during times of excess nutrient deficiency. It appears that the maintenance of long-livedfoliage in black spruce does not provide for greater flexibility in tree nutrient allocation. Their contribution to the carbon balance of the tree seems to be sufficient to explain their retention.
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    URL: http://dx.doi.org/10.1007/BF00317782
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  • 99
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    Early-spring gas exchange and uptake of deuterium-labelled water in the poikilohydric fernPolypodium virginianum (1993)
    Springer
    Oecologia 95 (1993), S. 9-13 
    Details
    ISSN: 1432-1939
    Keywords: Fern physiology ; Deuterium ; Water uptake ; Photosynthesis ; Leaf conductance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was carried out to determine if the desiccation-tolerant fernPolypodium virgimanum L. ecologically resembles lower plants by absorbing atmospheric water through its fronds and actively growing in early spring when the soil along cliff edges is still frozen. Three times between February and April, 1991,P. virginianum clonal mats were treated with deuterium-labelled water. Following each application, fronds were collected over several days and analyzed for the presence of deuterium. Two treatment groups plus a control were used: fronds were sprayed directly while covering the soil, or the roots were watered while protecting the fronds. The control mats were left untreated. Soil, air, and frond temperatures, plus photosynthesis and frond conductance were monitored throughout the study period. At subfreezing temperatures in February, no labelled water was taken up from the soil and no photosynthesis took place. Small amounts of label were absorbed from the soil in March during freeze-thaw cycles when rates of photosynthesis and stomatal conductance were both low. Large amounts of label were taken up from the soil in April when the soil was fully thawed and gas exchange was at normal seasonal levels. Label was not absorbed directly through the fronds when the plants were actively growing. Despite the desiccation tolerance ofP. virginianum, the timing and patterns of its water uptake and gas exchange in early spring resemble those found in higher vascular plants, not poikilohydric lower plants.
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  • 100
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    Water relations, gas exchange, and growth of resprouts and mature plant shoots of Arbutus unedo L. and Quercus ilex L. (1994)
    Springer
    Oecologia 98 (1994), S. 201-211 
    Details
    ISSN: 1432-1939
    Keywords: Growth ; Photosynthesis ; Resprouts ; Water relations ; Sclerophyll shrubs and trees
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Resprout and mature plant shoot growth, leaf water status and gas exchange behavior, tissue nutrient content, flowering, and production were studied for co-occurring shallow-rooted (Arbutus unedo L.) and deeprooted (Quercus ilex L.) Mediterranean tree species at the Collserola Natural Park in Northeast Spain Resprouts showed higher growth rates than mature plant shoots. During fall, no differences in eco-physiological performance of leaves were found, but mobilization of carbohydrates from burls strongly stimulated growth of fall resprouts compared to spring resprouts, despite low exposed leaf area of the fall shoots. During summer drought, resprouts exhibited improved water status and carbon fixation compared to mature plant shoots. Shoot growth of Q. ilex was apparently extended due to deep rooting so that initial slower growth during spring and early summer as compared to A. unedo was compensated. Tissue nutrient contents varied only slightly and are postulated to be of minor importance in controlling rate of shoot growth, perhaps due to the relatively fertile soil of the site. Fall flowering appeared to inhibit fall shoot growth in A. unedo, but did not occur in Q. ilex. The results demonstrate that comparative examinations utilizing vegetation elements with differing morphological and physiological adaptations can be used to analyze relatively complex phenomena related to resprouting behavior. The studies provide an important multi-dimensional background framework for further studies of resprouting in the European Mediterranean region.
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    URL: http://dx.doi.org/10.1007/BF00341473
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