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  • photosynthesis  (142)
  • Springer  (142)
  • American Meteorological Society
  • Institute of Physics
  • 1995-1999  (90)
  • 1990-1994  (52)
  • 1940-1944
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  • Springer  (142)
  • American Meteorological Society
  • Institute of Physics
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  • 1995-1999  (90)
  • 1990-1994  (52)
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  • 1
    Digitale Medien
    Digitale Medien
    Effect of nickel on certain physiological and biochemical behaviors of an acid tolerantChlorella vulgaris (1994)
    Springer
    BioMetals 7 (1994), S. 193-200 
    Details
    ISSN: 1572-8773
    Schlagwort(e): Chorella vulgaris ; acid tolerance ; ATPase ; nickel toxicity ; nutrient uptake ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract This study concerns the inhibitory effects of acid pH and nickel on growth, nutrient (NO3 - and NH4 +) uptake, carbon fixation, O2 evolution, electron transport chain and enzyme (nitrate reductase and ATPase) activities of acid tolerant and wild-type strains of Chlorella vulgaris. Though a general reduction in all these variables was noticed with decreasing pH, the tolerant strain was found to be metabolically more active than the wild-type. A reduced cation (NH4 +, Na+, K+ and Ca2+) uptake, coupled with a facilitated influx of anions (NH4 +, PO4 3- and HCO3 -), suggested the development of a positive membrane potential in acid tolerant Chlorella. Nevertheless, a tremendous increase in ATPase activity at decreasing pH revealed the involvement of superactive ATPase in exporting H+ ions and keeping the internal pH neutral. A difference in Na+ and K+ efflux of the two strains at decreasing pH suggests there is a difference in membrane permeability. The low toxicity of Ni in the acid tolerant strain may be due to the low Ni uptake brought about by a change in membrane potential as well as in permeability. Hence, the development of superactive ATPase and a change in both membrane potential and permeability not only offers protection against acidity, but also co-tolerance to metals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00140491
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  • 2
    Digitale Medien
    Digitale Medien
    The impact of elevated CO2 on growth and photosynthesis in Agrostis canina L. ssp. monteluccii adapted to contrasting atmospheric CO2 concentrations (1997)
    Springer
    Oecologia 110 (1997), S. 169-178 
    Details
    ISSN: 1432-1939
    Schlagwort(e): Key words Agrostis canina ; CO2 vents ; photosynthesis ; lignification ; growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  The aim of this study was to characterise growth and photosynthetic capacity in plants adapted to long-term contrasting atmospheric CO2 concentrations (C a). Seeds of Agrostis canina L. ssp. monteluccii were collected from a natural CO2 transect in central-western Italy and plants grown in controlled environment chambers at both ambient and elevated CO2 (350 and 700 μmol mol−1) in nutrient-rich soil. Seasonal mean C a at the source of the plant material ranged from 610 to 451 μmol CO2 mol−1, derived from C4 leaf stable carbon isotope discrimination (δ13C). Under chamber conditions, CO2 enrichment stimulated the growth of all populations. However, plants originating from elevated C a exhibited higher initial relative growth rates (RGRs) irrespective of chamber CO2 concentrations and a positive relationship was found between RGR and C a at the seed source. Seed weight was positively correlated with C a, but differences in seed weight were found to explain no more than 34% of the variation in RGRs at elevated CO2. Longer-term experiments (over 98 days) on two populations originating from the extremes of the transect (451 and 610 μmol CO2 mol−1) indicated that differences in growth between populations were maintained when plants were grown at both 350 and 700 μmol CO2 mol−1. Analysis of leaf material revealed an increase in the cell wall fraction (CWF) in plants grown at elevated CO2, with plants originating from high C a exhibiting constitutively lower levels but a variable response in terms of the degree of lignification. In vivo gas exchange measurements revealed no significant differences in light and CO2 saturated rates of photosynthesis and carboxylation efficiency between populations or with CO2 treatment. Moreover, SDS-PAGE/ LISA quantification of leaf ribulose bisphosphate carboxylase/oxygenase (Rubisco) showed no difference in Rubisco content between populations or CO2 treatments. These findings suggest that long-term adaptation to growth at elevated CO2 may be associated with a potential for increased growth, but this does not appear to be linked with differences in the intrinsic capacity for photosynthesis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004420050146
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  • 3
    Digitale Medien
    Digitale Medien
    Modification of carbonic anhydrase activity by antisense and over-expression constructs in transgenic tobacco (1994)
    Springer
    Plant molecular biology 25 (1994), S. 377-385 
    Details
    ISSN: 1573-5028
    Schlagwort(e): carbonic anhydrase ; antisense ; over-expression ; tobacco ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The activity and location of carbonic anhydrase has been modified by transformation of tobacco with antisense and over-expression constructs. Antisense expression resulted in the inhibition of up to 99% of carbonic anhydrase activity but had no significant impact on net CO2 assimilation. Stomatal conductance and susceptibility to water stress appeared to increase in response to the decline in carbonic anhydrase activity. An over-expression construct designed to increase cytosolic carbonic anhydrase abundance resulted in a significant increase in net activity, a small increase in stomatal conductance but little impact on CO2 assimilation. Chloroplastic carbonic anhydrase activity was enhanced by the expression of an additional construct which targeted the polypeptide to the organelle. The increase in chloroplastic carbonic anhydrase appeared to be accompanied by a concomitant increase in Rubisco activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00043867
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  • 4
    Digitale Medien
    Digitale Medien
    Over-production of the D1 protein of photosystem II reaction centre in the cyanobacterium Synechococcus sp. PCC 7942 (1994)
    Springer
    Plant molecular biology 26 (1994), S. 709-721 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; photosynthesis ; protein turnover ; psbA ; tac promoter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The unicellular cyanobacterium Synechococcus sp. PCC 7942 has three psbA genes encoding two different forms of the photosystem II reaction centre protein D1 (D1:1 and D1:2). The level of expression of these psbA genes and the synthesis of D1:1 and D1:2 are strongly regulated under varying light conditions. In order to better understand the regulatory mechanisms underlying these processes, we have constructed a strain of Synechococcus sp. PCC 7942 capable of over-producing psbA mRNA and D1 protein. In this study, we describe the over-expression of D1:1 using a tac-hybrid promoter in front of the psbAI gene in combination with lacI Q repressor system. Over-production of D1:1 was induced by growing cells for 12 h at 50 μmol photons m-2 s-1 in the presence of 40 or 80 μg/ml IPTG. The amount of psbAI mRNA and that of D1:1 protein in cells grown with IPTG was three times and two times higher, respectively. A higher concentration of IPTG (i.e., 150 μg/ml) did not further increase the production of the psbAI message or D1:1. The over-production of D1:1 caused a decrease in the level of D1:2 synthesised, resulting in most PSII reaction centres containing D1:1. However, the over-production of D1:1 had no effect on the pigment composition (chlorophyll a or phycocyanin/number of cells) or the light-saturated rate of photosynthesis. This and the fact that the total amounts of D1 and D2 proteins were not affected by IPTG suggest that the number of PSII centres within the membranes remained unchanged. From these results, we conclude that expression of psbAI can be regulated by using the tac promoter and lacI Q system. However, the accumulation of D1:1 protein into the membrane is regulated by the number of PSII centres.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00013756
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  • 5
    Digitale Medien
    Digitale Medien
    Over-production of the D1:2 protein makes Synechococcus cells more tolerant to photoinhibition of photosystem II (1996)
    Springer
    Plant molecular biology 30 (1996), S. 467-478 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene expression ; photosynthesis ; protein turnover ; psbA ; tac promoter ; D1 protein
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Over-expression of the psbAIII gene encoding for the D1 protein (form II; D1:2) of the photosystem II reaction centre in the Synechococcus sp. PCC 7942 was studied using a tac promoter and the lacI Q system. Over-expression was induced with 40 μg/ml IPTG in the growth medium for either 6 or 12 h at growth irradiance (50 μmol photons m-2 s-1). This treatment doubled the amount of psbAII/III mRNA and the D1:2 protein in membranes but decreased the amount of psbAI messages and the D1:1 protein. The total amount of both heterodimeric reaction centre proteins, D1 and D2, remained constant under growth light conditions, indicating that the number of PSII centres in the membranes was not affected, only the form of the D1 protein was changed from D1:1 to D1:2 in most centres. When the cells were photoinhibited either at 500 or 1000 μmol photons m-2 s-1, in the presence or absence of the protein synthesis inhibitor lincomycin, the D1:2 protein remained at a higher level in cells in which over-expression had been induced by IPTG. These cells were also less prone to photoinhibition of PSII. It is suggested that the tolerance of cells to photoinhibition increases when most PSII reaction centres contain the D1:2 protein at the beginning of high irradiance. This tolerance is further strengthened by maintaining psbAIII gene over-expression during the photoinhibitory treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00049325
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  • 6
    Digitale Medien
    Digitale Medien
    Effects of altered phosphoenolpyruvate carboxylase activities on transgenic C3 plant Solanum tuberosum (1996)
    Springer
    Plant molecular biology 32 (1996), S. 831-848 
    Details
    ISSN: 1573-5028
    Schlagwort(e): antisense ; Corynebacterium glutamicum ; Escherichia coli ; Flaveria trinervia ; overexpression ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phosphoenolpyruvate carboxylase (PEPC) genes from Corynebacterium glutamicum (cppc), Escherichia coli (eppc) or Flaveria trinervia (fppc) were transferred to Solanum tuberosum. Plant regenerants producing foreign PEPC were identified by Western blot analysis. Maximum PEPC activities measured in eppc and fppc plants grown in the greenhouse were doubled compared to control plants. For cppc a transgenic plant line could be selected which exhibited a fourfold increase in PEPC activity. In the presence of acetyl-CoA, a known activator of the procaryotic PEPC, a sixfold higher activity level was observed. In cppc plants grown in axenic culture PEPC activities were even higher. There was a 6-fold or 12-fold increase in the PEPC activities compared to the controls measured in the absence or presence of acetyl-CoA, respectively. Comparable results were obtained by transient expression in Nicotiana tabacum protoplasts. PEPC of C. glutamicum (PEPC C.g.) in S. tuberosum leaf extracts displays its characteristic K m(PEP) value. Plant growth was examined with plants showing high expression of PEPC and, moreover, with a plant cell line expressing and antisense S. tuberosum (anti-sppc) gene. In axenic culture the growth rate of a cppc plant cell line was appreciably diminished, whereas growth rates of an anti-sppc line were similar or slightly higher than in controls. Malate levels were increased in cppc plants and decreased in antisense plants. There were no significant differences in photosynthetic electron transport or steady state CO2 assimilation between control plants and transformants overexpressing PEPC C.g. or anti-sppc plants. However, a prolonged dark treatment resulted in a delayed induction of photosynthetic electron transport in plants with less PEPC. Rates of CO2 release in the dark determined after a 45 min illumination period at a high proton flux density were considerably enhanced in cppc plants and slightly diminished in anti-sppc plants. When CO2 assimilation rates were corrected for estimated rates of mitochondrial respiration in the light, the electron requirement for CO2 assimilation determined in low CO2 was slightly lower in transformants with higher PEPC, whereas transformants with decreased PEPC exhibited an appreciably elevated electron requirement. The CO2 compensation point remained unchanged in plants (cppc) with high PEPC activity, but might be increased in an antisense plant cell line. Stomatal opening was delayed in antisense plants, but was accelerated in plants overexpressing PEPC C.g. compared to the controls.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00020481
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  • 7
    Digitale Medien
    Digitale Medien
    Site-directed mutagenesis of the basic residues 321K to321 G in the CP 47 protein of photosystem II alters the chloride requirement for growth and oxygen-evolving activity in Synechocystis 6803 (1997)
    Springer
    Plant molecular biology 34 (1997), S. 455-463 
    Details
    ISSN: 1573-5028
    Schlagwort(e): photosystem II ; photosynthesis ; chlorophyll-binding protein ; Synechocystis ; oxygen evolution ; oligonucleotide-mediated mutagenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract CP 47, a component of photosystem II (PSII) in higher plants, algae and cyanobacteria, is encoded by the psbB gene. Site-specific mutagenesis has been used to alter a portion of the psbB gene encoding the large extrinsic loop E of CP 47 in the cyanobacterium Synechocystis 6803. Alteration of a lysine residue occurring at position 321 to glycine produced a strain with altered PSII activity. This strain grew at wild-type rates in complete BG-11 media (480 µM chloride). However, oxygen evolution rates for this mutant in complete media were only 60% of the observed wild-type rates. Quantum yield measurements at low light intensities indicated that the mutant had 66% of the fully functional PSII centers contained in the control strain. The mutant proved to be extremely sensitive to photoinactivation at high light intensities, exhibiting a 3-fold increase in the rate of photoinactivation. When this mutant was grown in media depleted of chloride (30 µM chloride), it lost the ability to grow photoautotrophically while the control strain exhibited a normal rate of growth. The effect of chloride depletion on the growth rate of the mutant was reversed by the addition of 480 µM bromide to the chloride-depleted BG-11 media. In the presence of glucose, the mutant and control strains grew at comparable rates in either chloride-containing or chloride-depleted media. Oxygen evolution rates for the mutant were further depressed (28% of control rates) under chloride-limiting conditions. Addition of bromide restored these rates to those observed under chloride-sufficient conditions. Measurements of the variable fluorescence yield indicated that the mutant assembled fewer functional centers in the absence of chloride. These results indicate that the mutation K321G in CP 47 affects PSII stability and/or assembly under conditions where chloride is limiting.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005826411702
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  • 8
    Digitale Medien
    Digitale Medien
    Random chemical mutagenesis of a specific psbDI region coding for a lumenal loop of the D2 protein of photosystem II in Synechocystis sp. PCC 6803 (1996)
    Springer
    Plant molecular biology 30 (1996), S. 243-254 
    Details
    ISSN: 1573-5028
    Schlagwort(e): Cyanobacteria ; photosynthesis ; random mutagenesis ; sodium bisulfite ; thylakoids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract To identify amino acid residues of the D2 protein that are critical for functional photosystem II (PS II), sodium bisulfite was utilized for in vitro random mutagenesis of the psbDI gene from Synechocystis sp. PCC 6803. Sodium bisulfite reacts specifically with cytosine in single-stranded regions of DNA and does not attack double-stranded DNA. Using a hybrid plasmid that was single-stranded in the region to be mutagenized and that was double-stranded elsewhere, mutations were targeted to a specific psbDI region coding for the lumenal A-B loop of the D2 protein. Several mutants were isolated with a total of 15 different amino acid changes in the loop. The majority of these mutations did not result in a loss of photoautotrophic growth or in significantly altered PS II function. However, mutation of Glu-69 to Lys, Ser-79 to Phe, and Ser-88 to Phe were found to influence photosystem II activity; the importance of the latter two residues for proper PS II function was unexpected. Cells carrying the double mutation S79F/S88F in D2 did not grow photoautotrophically and had no functionally active PS II centers. The single mutant S79F was also incapable of photoautrophic growth, but displayed reasonably stable oxygen evolution, while PS II function in the single mutant S88F appeared to be close to normal. Because of the more pronounced phenotype of the S79F/S88F strain as compared to the single mutants, both Ser residues appear to affect stable assembly and function of the PS II complex. The mechanism by which the S79F mutant loses photoautotrophic growth remains to be established. However, these results show the potential of targeted random mutagenesis to identify functionally important residues in selected regions of proteins.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00020111
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  • 9
    Digitale Medien
    Digitale Medien
    Yield, water use efficiency and nitrogen uptake in potato: influence of drought stress (1997)
    Springer
    Potato research 40 (1997), S. 19-34 
    Details
    ISSN: 1871-4528
    Schlagwort(e): water stress ; photosynthesis ; stress index ; dry matter partitioning ; tuber quality ; Solanum tuberosum L.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary A lysimeter experiment was performed to study the optimal allocation of limited water supply in potatoes. Irrigation regimes equal to 40, 60 and 80% of maximum evapotranspiration (ET) were evenly applied over the crop cycle. Other treatments involved withholding 80 mm of irrigation, based on ET, beginning at each of three designated growth stages (tuber initiation, early and late tuber growth). An irrigated control treatment, restoring the entire ET, was included for comparison. Continuous drought stress reduced photosynthesis as irrigation volumes were reduced. Plant biomass and tuber yield decreased almost proportionally to water consumption, so that WUE was roughly constant. N uptake was highest in the control and in 80% ET treatment. Withholding water during tuberisation severely hindered plant physiological processes and penalized tuber yield. Reductions in photosynthesis, total biomass and yield were the greatest when drought was imposed during tuber initiation. The earliest stress resulted in the lowest WUE and N uptake. A new crop water stress index (SI) was proposed, which combines atmospheric demand for water and canopy temperature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02407559
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  • 10
    Digitale Medien
    Digitale Medien
    Drought-dependent responses of photosynthesis, transpiration and water use efficiency of Japanese cypress and Japanese red pine seedlings (1996)
    Springer
    Journal of forest research 1 (1996), S. 73-78 
    Details
    ISSN: 1610-7403
    Schlagwort(e): Chamaecyparis obtusa Endl. ; photosynthesis ; Pinus densiflora Sieb. et Zucc. ; stomatal conductance ; water stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This study was conducted to investigate the potential for modifying drought tolerance of Japanese cypress (Chamaecyparis obtusa Endl.) and Japanese red pine (Pinus densiflora Sieb. et Zucc.). Three-year-old seedlings were controlled for five-months at three different soil water potentials ({ie73-1}). Japanese cypress exposed to high {ie73-2} was able to maintain higher photosynthesis (Phn), transpiration (Tr) and stomatal conductance to H2O (gH2O) in comparison to low {ie73-3} pretreatments, however, there was no significant difference in Phn for Japanese red pine. Soil water potential at the threshold from the maximum to limited Phn was higher in high {ie73-4} pretreatments than in low {ie73-5} pretreatments. Net photosynthesis, Tr and gH2O decreased more rapidly in high {ie73-6} pretreatments than in low {ie73-7} pretreatments. Transpiration decreased more significantly than Phn, thus, resulted in increased water use efficiency. All these factors are likely to result in significant improvements in the drought tolerance. Japanese red pine seems more drought-tolerant than Japanese cypress. Japanese cypress is suitable to soil of −0.05 MPa water potential, and Japanese red pine is suitable to −0.16 MPa and even dryer soils.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02348307
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  • 11
    Digitale Medien
    Digitale Medien
    Simultaneous measurements of quantum yield and CO2 uptake for the assessment of non-assimilative electron flow in tree leaves (1996)
    Springer
    Journal of forest research 1 (1996), S. 79-85 
    Details
    ISSN: 1610-7403
    Schlagwort(e): chlorophyll fluorescence ; electron transport ; photorespiration ; photosynthesis ; quantum yield ; tree
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Using attached and detached leaves ofAcer palmatum Thunb. andRhaphiolepsis umbellata Makino, pulse-modulated chlorophyll fluorescence and CO2 exchange were measured. Quantum yield of photosynthesis was determined from the fluorescence parameter(Fm′−Fs)/Fm′, where (Fm′−Fs) was defined as the difference between steady state chlorophyll fluorescence (Fs) and maximum fluorescence (Fm′) elicited by a saturating light pulse. The rate of electron transport through photosystem II (total electron flow) was calculated from the product of quantum yield andA (PFD), whereA is the rate of absorbed photons as given by leaf absorptance, and PFD is the photon flux density at the leaf surface. The rate of electron transport dependant on CO2 uptake (assimilative electron flow) was calculated from the gross photosynthetic rate in a leaf. The difference between the rates of total and assimilative electron transport was denoted as the rate of non-assimilative electron transport which depends on photorespiration and oxygen reduction. Available data provided quantitative information on the rate of non-assimilative electron flow in intact leaves. When leaf photosynthesis ofA. palmatum was measured under sunlight, the rates of total and assimilative electron transport were determined to be approximately 900 and 150 μmol equiv. e/mg Chl·h, respectively. The difference (750 μmol equiv. e/mg Chl·h) was attributed to the activity of non-assimilative electron flow. The ratio of total to assimilative electron flow was found to increase gradually with rising in irradiance. The results suggest that non-assimilative electron flow occurred at much higher rate than assimilative electron flow at high irradiance. Implications of the results are briefly discussed in relation to photosynthesis limitation in tree leaves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02348308
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  • 12
    Digitale Medien
    Digitale Medien
    Iron deprivation in cyanobacteria (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 199-210 
    Details
    ISSN: 1573-5176
    Schlagwort(e): cyanobacteria ; iron deficiency ; photosynthesis ; siderophores ; flavodoxin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Iron is an essential component of electron transport in almost all living organisms. It is particularly important to phototrophs like cyanobacteria because 22–23 irons are required for a complete functional photosynthetic apparatus. Since the low solubility of Fe+++ above neutral pH in oxic ecosystems severely limits the biological availability of iron to aquatic microorganisms, cyanobacteria and other microbes have developed a number of responses to cope with iron deficiency. Cyanobacterial responses to iron stress include the synthesis of an efficient, siderophore-based system to scavenge iron and the substitution of ferredoxin with flavodoxin. An additional response in cyanobacteria involves the alteration of the light-harvesting apparatus that includes the appearance of a new, iron-stress-induced, photosystem II, chlorophyll-binding protein. Although cytochromec-553 has a potential non-iron-containing replacement in plastocyanin, a copper-containing protein, iron stress appears to favor the utilization of cytochromec-553 because siderophores also bind copper and form a complex that is excluded from the cell. This paper is intended primarily as a review of molecular and physiological responses of actively growing cyanobacterial cultures to conditions of iron stress, where iron is present but essentially insoluble, and to differentiate these responses from iron starvation, where the amount of iron in the system is not sufficient for cell growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02186073
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  • 13
    Digitale Medien
    Digitale Medien
    Molecular genetics of the cyanobacteriumSynechocystis sp. PCC 6803: Principles and possible biotechnology applications (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 263-273 
    Details
    ISSN: 1573-5176
    Schlagwort(e): molecular biology ; mutagenesis ; photosynthesis ; protein engineering ; respiration ; thylakoid membranes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The cyanobacteriumSynechocystis sp. PCC 6803 is readily amenable to targeted mutagenesis: Foreign DNA is taken up spontaneously, and after uptake DNA can be integrated into the organism's genome by homologous recombination. Using appropriate DNA constructs for transformation, specific genes in the organism can be interrupted, deleted, or replaced by modified gene copies. The organism can grow under a number of different conditions, ranging from photoautotrophic to fully heterotrophic modes, making genetic modifications that alter fundamental processes such as photosynthesis and/or respiration feasible. For example, deletion of photosystem I leads to an obligate (photo)heterotrophic strain in which photosystem II-generated electrons appear to be consumed by respiratory processes, whereas deletion of photosystem II leads to an obligate (photo)heterotrophic strain in which cyclic electron flow around photosystem I appears to remain active. A major advantage ofSynechocystis sp. PCC 6803 is that its entire genome has been sequenced (by S. Tabata and co-workers), opening many avenues to address basic and applied research problems. For example, genes can be introduced, modified or deleted, and hypotheses regarding the function of an open reading frame can be tested by deletion of this open reading frame. Methods to modify genes are numerous. In addition to site-directed mutagenesis, novel molecular genetic approaches including ‘targeted random mutagenesis’, combinatorial mutagenesis and introduction of hybrid genes have come of age and have proven to be very powerful tools in protein engineering. These approaches have been utilized primarily in this strain to study photosynthesis, but applications of this technology, including pathway engineering, alterations of substrate specificity of enzymes and introduction of tolerance to a variety of stresses, are equally feasible in relation to more applied aims. For optimal utilization of the potential of theSynechocystis sp. PCC 6803 system, however, an increased emphasis toward understanding the biochemistry and molecular physiology of cyanobacteria will also be critically important.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02178569
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  • 14
    Digitale Medien
    Digitale Medien
    In situ monitoring of chlorophyll fluorescence to assess the synergistic effect of low temperature and high irradiance stresses inSpirulina cultures grown outdoors in photobioreactors (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 283-291 
    Details
    ISSN: 1573-5176
    Schlagwort(e): fluorescence ; photoinhibition ; photosynthesis ; Spirulina ; photobioreactor ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A chlorophyll fluorescence technique was applied to anin situ study on the effects of low temperature and high light stresses onSpirulina cultures grown outdoors in controlled tubular photobioreactors at high (1.1 g L−1) and low (0.44 g L−1) biomass concentrations. Diurnal changes in PSII photochemistry (F v/F m) after 15 min of darkness, or in the light (dF/F′ m), and non-photochemical (qN) quenching were measured using a portable, pulse-amplitude-modulated fluorometer. The depression of theF v/F m ratio ofSpirulina cultures grown outdoors at 25°C (i.e. 10°C below optimum for growth) and 0.44 g L−1, reached 30% at the middle of the day. At the same time of the day thedF/F′ m ratio showed a reduction of up to 52%. The depression of bothF v/F m anddF/F′ m was lower in the cultures grown at 1.1 g L−1. Photoinhibition reduced the daily productivity of the culture grown at 0.44 g L−1 and 25°C by 33% with respect to that grown at 35°C. Changes in the growth yields of the cultures grown under different temperatures and growth rates correlate well with analogous changes in photon yield (dF/F′ m). Simple measurements of photochemical yield (F v/F m) can be used to test the physiological status ofSpirulina cultures. The results indicate that the saturating pulse fluorescence technique, when usedin situ, is a powerful tool for assessment of the photosynthetic characteristics of outdoor cultures ofSpirulina.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02178571
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  • 15
    Digitale Medien
    Digitale Medien
    Use of chlorophyll fluorescence to estimate the effect of photoinhibition in outdoor cultures ofSpirulina platensis (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 31-34 
    Details
    ISSN: 1573-5176
    Schlagwort(e): fluorescence ; photoinhibition ; photosynthesis ; Spirulina ; temperature
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chlorophyll fluorescence measurements were used to evaluate the effect of temperature on photoinhibition inSpirulina platensis cultures grown in tubular reactors outdoors. Cultures grown at 35 °C during the day time showed a lower reduction in the Fv/Fm ratio as compared to cultures grown at 25 °C. It is demonstrated that the lower temperature photoinhibited cells can undergo a complete recovery once transferred to low light and higher temperature. This recovery does not take place when 100 µg ml-1 chloramphenicol is added to cells. The recovery is light dependent and cells incubated in the dark at low temperature do not show a recovery in the Fv/Fm ratio. The data presented strongly support the hypothesis that photoinhibition takes place in outdoorSpirulina cultures. At the same time it is demonstrated that fluorescence measurements can be used as a fast reliable indication for photoinhibition in outdoor algal cultures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02185901
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  • 16
    Digitale Medien
    Digitale Medien
    Use of macroalgae for marine biomass production and CO2 remediation: a review (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 45-60 
    Details
    ISSN: 1573-5176
    Schlagwort(e): biofilter ; biofuels ; CO2 ; macroalgae ; marine biomass ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Biomass production from macroalgae has been viewed as important mainly because of the need for pollution abatement. Environmental considerations will increasingly determine product and process acceptability and drive the next generation of economic opportunity. Some countries, including Japan, are actively promoting "green" technologies that will be in demand worldwide in the coming decades. Should an international agreement on CO2-reduction be ratified, its effective use for energy production would be of high priority. This report shows that macroalgae have great potential for biomass production and CO2 bioremediation. Macroalgae have high productivity, as great or greater than the most productive land plants, and do not compete with terrestrial crops for farm land. The review focuses on recent data on productivity, photosynthesis, nutrient dynamics, optimization and economics. Biomass from macroalgae promises to provide environmentally and economically feasible alternatives to fossil fuels. Nevertheless, the techniques and technologies for growing macroalgae on a large-scale and for converting feedstocks to energy carriers must be more fully developed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02185904
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  • 17
    Digitale Medien
    Digitale Medien
    Selective effect of the herbicide DCMU on unicellular algae — a potential tool to maintain monoalgal mass culture ofNannochloropsis (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 415-419 
    Details
    ISSN: 1573-5176
    Schlagwort(e): herbicide ; DCMU ; photosynthesis ; monoalgal culture ; Chaetoceros ; Dunaliella ; Nannochloropsis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The selective effect of DCMU on photosynthetic activity and growth rate was examined in several marine unicellular algae:Nannochloropsis sp. (Eustigmatohyceae),Dunaliella salina (Chlorophyceae)Isochrysis galbana (Prymnesiophyceae) andChaetoceros sp. (Bacillariophyceae). DCMU at 10−7 M caused an immediate decrease in the photosynthetic rate ofDunaliella andIsochrysis (about 50% inhibition), whereas 10−6 M imposed 80% inhibition in the photosynthetic rate ofChaetoceros. InNannochloropsis the rate was affected only when DCMU concentration exceeded 10−6M. Cellular growth rate of all studied algae was affected by DCMU in a similar manner to photosynthesis. The differential effect of DCMU was further examined in mixed cultures in whichNannochloropsis was cultivated together with an additional species simulating a contamination situation of aNannochloropsis culture. When DCMU was added at concentrations higher than 10−7 M, the growth of the competing algae significantly decreased, whileNannochloropsis maintained a relatively high growth rate. Consequently, after a growth period of 4 to 7 days a clear domination ofNannochloropsis was observed. These results demonstrate that DCMU and probably other herbicides of similar characteristics can be used effectively as a selective tool to suppress contaminating unicellular algae in open ponds in order to maintain a monoculture ofNannochloropsis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02178586
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  • 18
    Digitale Medien
    Digitale Medien
    Role of light and photosynthesis on the acclimation process of the cyanobacteriumSpirulina platensis to salinity stress (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 119-124 
    Details
    ISSN: 1573-5176
    Schlagwort(e): Spirulina platensis ; cyanobacterium ; NaCl ; photoinhibition ; photosynthesis ; photosystem II ; salt stress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The response ofSpirulina platensis cells to salinity stress was studied. Once adapted to the higher osmoticum, photosynthetic parameters such as the maximum rate of photosynthesis under saturating irradiance (Pmax) and the initial slope of the P-I curve (α) are reduced by 15% and 25% in 0.5 M NaCl grown cells, respectively. Salt-adapted cells have a modified biochemical composition; reduced protein and chlorophyll content, and an increased level of carbohydrates. The reduction in the photosynthetic capacity of the salt-adaptedSpirulina cells reflects a lower ability to utilize light energy and results in an increase in the susceptibility of the stressed cells to photoinhibition. This conclusion is supported by the finding that cultures exposed to salt stress show not only a decrease in growth rate (μ), but lose the ability to respond to increased irradiance with an increase in growth. The use of variable fluorescence as a fast and reliable measurement to follow the changes in PSII of salt-stressesSpirulina cells enables following the early events of salinity shock. It indicates that as soon as the cells are exposed to salt, a protection mechanism is induced. This mechanism does not require any protein synthesis and may take place even in the dark, though at somewhat reduced effectiveness. The significance of the result in providing a better understanding of the interaction between two environmental stresses — light and salinity — and their application in the outdoor mass cultivation ofSpirulina are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02186314
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  • 19
    Digitale Medien
    Digitale Medien
    What kind of lamp for the cultivation of algae? (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 309-313 
    Details
    ISSN: 1573-5176
    Schlagwort(e): light source ; emission spectrum ; photosynthesis ; algae ; absorption ; efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A method for quantitative evaluation of light sources from the point of their suitability for algal cultivation is described. Two parameters are used for the evaluation: (1) amount of photons emitted in the spectral region absorbed by algae per consumed unit of electrical energy; (2) fraction of photons intercept by the algae that got effectively transformed into chemical energy. The value of parameter (2) depends on the emission spectrum of the light source, the absorption spectrum of the algae, quantum capacity of the algae and on conditions of cultivation. The method permits the assessment of the differences in algal productivity under light of various light sources with respect to other recent methods for comparison.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02181944
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  • 20
    Digitale Medien
    Digitale Medien
    Light acclimation and photoinhibition in threeSpirulina platensis (cyanobacteria) isolates (1996)
    Springer
    Journal of applied phycology 8 (1996), S. 35-40 
    Details
    ISSN: 1573-5176
    Schlagwort(e): cyanobacteria ; light intensity ; photoinhibition ; photosynthesis ; recovery ; Spirulina platensis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Three isolates ofSpirulina platensis (Norst) Geitler marked BP, P4P and Z19/2 were compared with respect to their response and acclimation capability to high photon flux densities (HPFD). Cultures exposed to HPFD (1500–3500 μmol photon m−2 s−1) exhibited a marked decrease in light-dependent O2 evolution rate. P4P was more sensitive to HPFD than the two other isolates. All three isolates recovered from photoinhibition when placed under low PFD. The BP isolate was able to recover also in the dark but to a lower extent and at a lower rate, while no recovery was observed in the other two isolates under dark conditions. No recovery was observed when protein synthesis was inhibited using chloramphenicol. Cultures grown at 200 μmol photon m−2 s−1 differed from cultures grown at 120 μmol photon m 2 s-1 by their lower maximal photosynthetic rate (P max ) and higher light saturation (I k ) value, while being more resistant to HPFD stress. The ability ofSpirulina isolates to acclimate and withstand HPFD may provide useful information for the selection of strains useful for outdoor mass cultivation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02186220
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  • 21
    Digitale Medien
    Digitale Medien
    Influence of tidal location on morphology, photosynthesis and pigments of the agarophyte, Gelidiella acerosa, from Northern Philippines (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 525-532 
    Details
    ISSN: 1573-5176
    Schlagwort(e): Gelidiella ; agarophyte ; photosynthesis ; P-I curve ; morphology ; tide ; pigment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The red seaweed agarophyte, Gelidiella acerosa (Forsskål) (Feldmann& Hamel) was collected from tidepools, high intertidal rocks. and shallow subtidal are as along a reef flat in Ilocos Norte, northern Philippines. The three populations were compared during the summer (dry) and rainy (wet) seasons to determine changes in morphology and photoacclimation capacity as possible use in mariculture. During summer months (February toApril) after exposure to environmental extremes (i.e. the highest percent of minus tides during daylight, high light regimes, desiccation, and solar bleaching), the populations differed in their morphologies and responses to increasing irradiance levels (P–I curve). Tidepool plants were the tallest, bushiest, and with increased diameter of cortical cells; while,high intertidal plants were the shortest, with sparse branching pattern and decreased diameter of cortical cells. Although their saturation irradiances indicated shade tolerance (Ik = 52 − 112 µmol photon m -2 s-1). their differential light saturation curves (P-I curves) suggested a capacity to acclimate to ambient light regimes. For example, plants from the high intertidal zone showed higher photosynthetic rates and saturation irradiances, slightly lower initial slopes of the P-I curves and levels of light harvesting accessory pigments, rphycoerhythrin (R-PE) and rphycocyanin (R-PC), after being exposed to higher light regimes. In contrast, plants from tidepools and shallow subtidal areas had lower photosynthetic rates and saturation irradiances, slightly steeper initial slopes of the P-I curves and levels of R-PE and R-PC, having been exposed to lower light regimes. During the rainy months (June to November) no significant responses in these parameters were recorded. Comparison of the P-I responses of vegetative and tetrasporic plants showed these to vary with season. The data suggest that when plants became reproductive their physiological fitness either was unchanged or slightly enhanced. These results indicate that all three populations of G. acerosa could be used as seed stock for mariculture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007968201873
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  • 22
    Digitale Medien
    Digitale Medien
    Improvement of photosynthesis in dense microalgal suspension by reduction of light harvesting pigments (1997)
    Springer
    Journal of applied phycology 9 (1997), S. 503-510 
    Details
    ISSN: 1573-5176
    Schlagwort(e): Chlorella pyrenoidosa ; dense algalsuspension ; light-harvesting pigment ; photosynthesis ; Synechocystis PCC 6714
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of light-harvesting pigments (LHP) inmicroalgal cells on photosynthetic activity in adense cell suspension were examined. The results suggest that a lower LHP content should result in higher photosynthetic productivity under high light intensity. The idea was first proposed by Lien and San Pietro in 1975 that photosynthesis could be improved by reducing the LHP content in microalgal cells, but this has not been demonstrated in detail. Experiments to evaluate the idea were conducted with Synechocystis PCC6714 and Chlorellapyrenoidosa. In the experiments with PCC 6714, photosynthesis of a phycocyanin-deficient mutant was compared with that of the wild type. In the experiments with C. pyrenoidosa, the LHP content was controlled by the light intensity in the algalculture. The maximum photosynthetic activity was 20–30% higher in the dense suspension of cells having a lower LHP content with both organisms. These results indicate that the idea of reducing the LHP contentcould be applicable to a wide variety of photosynthetic organisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007920025419
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  • 23
    Digitale Medien
    Digitale Medien
    The interactive effects of UV-B radiation and a herbicide on uptake and allocation of carbon in two strains of the green algaScenedesmus (1997)
    Springer
    Aquatic ecology 31 (1997), S. 261-272 
    Details
    ISSN: 1573-5125
    Schlagwort(e): sherbicide tolerance ; photosynthesis ; phytoplankton ; simetryn ; triazine ; herbicides ; ultraviolet radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We examined the effects of UV B radiation on14C-uptake rates and carbon assimilation into the major end-products of photosynthesis of the green algaScenedesmus in the presence and absence of the triazine herbicide simetryn. Experiments were conducted using both a herbicide-susceptible and herbicide-tolerant strains ofScenedesmus. Three different UV-B dose rates were used as well as a light control. The lowest dose rate was almost the same level as in subsurface of ponds and lakes, while the other two were slightly lower and higher than natural sunlight on the surface of ponds and lakes, respectively. Total uptake rates of14C were not reduced by the UV B irradiation alone even at the highest dose rate. However, in the presence of the herbicide, uptake rates were clearly reduced by the highest dose rate of UV-B concomitant with increasing herbicide concentrations in the herbicide-susceptible strain. On the other hand, the proportion of lipid fraction was slightly reduced by all the UV-B treatments in the herbicide-susceptible strain even in the absence of the herbicide. In the herbicide-tolerant strain, uptake rates were not affected by UV-B radiation or by the herbicide. These facts indicated that UV-B effects could be smaller than predicted. It may be important to examine combined effects of UV-B and other anthropogenic and/or natural stresses for assessing actual UV-B effects in the field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02493513
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  • 24
    Digitale Medien
    Digitale Medien
    Turbulence in mass algal cultures and the role of light/dark fluctuations (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 331-335 
    Details
    ISSN: 1573-5176
    Schlagwort(e): turbulence ; photosynthesis ; Chlorella ; light/dark cycles ; mass transfer rates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In mass algal cultures, some form of agitation is usually provided; among other effects, this moves the organisms though an optically dense profile and provides mixing. During this transport, medium frequency fluctuations in the light energy supply are perceived by the algae, which are of the order of 1 Hz and less. It has been suggested that turbulence with the resultant light/dark cycles of medium frequency enhances productivity. However, turbulence has two major influences in a well mixed system: it facilitates fluctuating light regimes and increases the transfer rates between the growth medium and the cultured organism. An estimation of productivity as oxygen liberation was measured under laminar and turbulent flow rates, and varying light/dark ratios. Increased turbulence, which increased exchange rates of nutrients and metabolites between the cells and their growth medium, together with increased light/dark frequencies, increased productivity and photosynthetic efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02181947
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  • 25
    Digitale Medien
    Digitale Medien
    Seasonal and spatial patterns in phytoplankton photosynthetic parameters in a tidal freshwater river (1997)
    Springer
    Hydrobiologia 364 (1997), S. 199-208 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Phytoplankton ; photosynthesis ; light ; temperature ; tidal freshwater ; irradiance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The photosynthetic response to irradiance wasquantified for phytoplankton from the tidalfreshwater Potomac River biweekly to monthly over aperiod of six years. Samples were collected from twoshallow embayments and portions of the deeper rivermainstem. Photosynthetic rate was measured in thelaboratory at in situ temperature over a range ofirradiance levels and photosynthetic parameters werecalculated using nonlinear regression.PB max,the maximum photosynthetic ratestandardized to chlorophyll a, increased withtemperature up to 25 °C with a Q10 of 2.02. Above 25 °C, PB max was essentiallyconstant with temperature. Lesser correlationbetween PB max and ambient irradiance couldbe explained by the correlation of irradiance withtemperature. α, the slope of the P–I curve atlow light, was correlated with both ambientirradiance and temperature. Highest α valueswere found in late summer when high temperature andintermediate ambient irradiance were observed. Spring and early summer were characterized by lowα. Despite low light penetration, Ik andα values were indicative of sun limitationpossibly due to intermittent high light levelsexperienced during mixing. Ik showed a clearseasonal trend directly related to days from summersolstice. Spatial patterns were minimal except thatIk was consistently lower in one shallowembayment than in the other two areas. Seasonalpatterns in photosynthetic parameters correspondedroughly to changes from a spring diatom populationto summer cyanobacterial assemblage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003107306421
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  • 26
    Digitale Medien
    Digitale Medien
    New method for toxicity assessment in marine and brackish environments using the macroalga Gracilaria tenuistipitata (Gracilariales, Rhodophyta) (1996)
    Springer
    Hydrobiologia 326-327 (1996), S. 317-325 
    Details
    ISSN: 1573-5117
    Schlagwort(e): biotest ; brackish ; Gracilaria ; growth inhibition ; marine ; photosynthesis ; Rhodophyta ; seaweed ; toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A growth inhibition test method was developed using the macroalga Gracilaria tenuistipitata as the test organism. This alga was chosen because of its high laboratory growth rates, commonly 30–40% d−1, which are reached in salinities between 5 and 40‰, and its epiphyte resistance. The toxicity of a number of substances, including heavy metals, herbicides and complex wastewaters towards the alga was assayed. Anti-fouling paints were tested with a modification of the method. EC50 values for heavy metals varied between 0.05 and 17 mg l−1 and for herbicides between 0.002 and 0.02 mg l−l. The sensitivity to the toxicant was generally higher at low salinity. Omitting nitrogen and phosphorus additions to the test medium increased the sensitivity and a semi-static performance was possible with maintained or increased sensitivity. Preliminary tests done with a computerised photosynthesis inhibition method produced promising results. In conclusion, this is a simple, sensitive and reproducible test method for assessing the toxicity of substances, wastewaters and anti-fouling paints in brackish and marine environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00047825
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  • 27
    Digitale Medien
    Digitale Medien
    Gas exchange responses of a mangrove species, Avicennia marina, to waterlogged and drained conditions (1997)
    Springer
    Hydrobiologia 352 (1997), S. 39-47 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Avicennia marina ; gas exchange ; mangroves ; photosynthesis ; waterlogging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This study was undertaken in summer on fully expanded leaves of Avicennia marina trees in the Beachwood Mangroves Nature Reserve, Durban,South Africa. Data sets were obtained over 5–7 days of relatively dry conditions and over two periods of 5 days during which the swamp was continuously inundated with dilute seawater (〈 150 mol m−3NaCl). Gas exchange responses were strongly influenced by photosynthetic photon flux density (PPFD), leaf temperature and leaf to air vapour pressure deficit (Δw). Carbon dioxide exchange was saturated at a PPFD of about 800 µmol m−2 s−1. Maximal CO2 exchange rates ranged from 8.5 to 9.9 µmol m−2 s−1 with no differences between drained and waterlogged conditions. Under drained conditions, leaf conductance,transpiration and internal CO2 concentrations were generally lower, and water use efficiencies higher, than during waterlogging. Continuous waterlogging for 5 days had no adverse effect on CO2 exchange. Xylem water potentials ranged from −1.32to −3.53 MPa during drained and from −1.02 to −2.65 Mpa during waterlogged conditions. These results are discussed in relation to anatomical and metabolic adaptations of A. marina to waterlogging stress.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003088803335
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  • 28
    Digitale Medien
    Digitale Medien
    Lumenal proteins involved in respiratory electron transport in the cyanobacterium Synechocystis sp. PCC6803 (1997)
    Springer
    Plant molecular biology 35 (1997), S. 407-416 
    Details
    ISSN: 1573-5028
    Schlagwort(e): cyanobacteria ; cytochrome oxidase ; electron transport ; photosynthesis ; respiration ; thylakoids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Cyanobacterial thylakoids catalyze both photosynthetic and respiratory activities. In a photosystem I-less Synechocystis sp. PCC 6803 strain, electrons generated by photosystem II appear to be utilized by cytochrome oxidase. To identify the lumenal electron carriers (plastocyanin and/or cytochromes c 553, c 550, and possibly c M) that are involved in transfer of photosystem II-generated electrons to the terminal oxidase, deletion constructs for genes coding for these components were introduced into a photosystem I-less Synechocystis sp. PCC 6803 strain, and electron flow out of photosystem II was monitored in resulting strains through chlorophyll fluorescence yields. Loss of cytochrome c 553 or plastocyanin, but not of cytochrome c 550, decreased the rate of electron flow out of photosystem II. Surprisingly, cytochrome c M could not be deleted in a photosystem I-less background strain, and also a double-deletion mutant lacking both plastocyanin and cytochromec 553 could not be obtained. Cytochrome c M has some homology with the cytochrome c-binding regions of the cytochromecaa3 -type cytochrome oxidase from Bacillus spp. and Thermus thermophilus. We suggest that cytochrome c M is a component of cytochrome oxidase in cyanobacteria that serves as redox intermediate between soluble electron carriers and the cytochromeaa3 complex, and that either plastocyanin or cytochrome c 553 can shuttle electrons from the cytochrome b6f complex to cytochrome c M.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005875124387
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  • 29
    Digitale Medien
    Digitale Medien
    Control of Photosystem II in spinach leaves by continuous light and by light pulses given in the dark (1996)
    Springer
    Photosynthesis research 50 (1996), S. 181-191 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll fluorescence ; energy dissipation ; light scattering ; photosynthesis ; state transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The light-induced induction of components of non-photochemical quenching of chlorophyll fluorescence which are distinguished by different rates of dark relaxation (qNf, rapidly relaxing and qNs, slowly relaxing or not relaxing at all in the presence brief saturating light pulses which interrupt darkness at low frequencies) was studied in leaves of spinach. After dark adaptation of the leaves, a fast relaxing component developed in low light only after a lag phase. Quenching increased towards a maximum with increasing photon flux density. This ‘fast’ component of quenching was identified as energy-dependent quenching qE. It required formation of an appreciable transthylakoid ΔpH and was insignificant when darkened spinach leaves received 1 s pulses of light every 30 s even though zeaxanthin was formed from violaxanthin under these conditions. Another quenching component termed qNs developed in low light without a lag phase. It was not dependent on a transthylakoid pH gradient, decayed exponentially with a long half time of relaxation and was about 20% of total quenching irrespective of light intensity. When darkened leaves were flashed at frequencies higher than 0.004 Hz with 1 s light pulses, this quenching also appeared. Its extent was very considerable, and it did not require formation of zeaxanthin. Relaxation was accelerated by far-red light, and this acceleration was abolished by NaF. We suggest that qNs is the result of a so-called state transition, in which LHC II moves after its phosphorylation from fluorescent PS II to nonfluorescent PS I. This state transition was capable of decreasing in darkened leaves the potential maximum quantum efficiency of electron flow through Photosystem II by about 20%.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014888
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  • 30
    Digitale Medien
    Digitale Medien
    Cobalt induced changes in photosystem activity in Synechocystis PCC 6803: Alterations in energy distribution and stoichiometry (1996)
    Springer
    Photosynthesis research 50 (1996), S. 243-256 
    Details
    ISSN: 1573-5079
    Schlagwort(e): cyanobacteria ; electron transport ; fluorescence ; photosynthesis ; spillover ; state changes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Adaptive responses to excess (supraoptimal) level of cobalt supplied to the growth medium were studied in the cyanobacterium Synechocystis PCC 6803. Growth of cells in the medium containing 10 μM CoCl2 led to a large stimulation (50%) in O2-evolution and an overall increase (∼30%) in the photosynthetic electron transport rates. Analysis of variable Chl a fluorescence yield of PS II and immuno-detection of Photosystem II (PS II) reaction-center protein D1, showed a small increase (15–20%) in the number of PS II units in cobalt-grown cells. Cobalt-grown cells, therefore, had a slightly elevated PS II/PS I ratio compared to control. We observed alteration in the extent of energy distribution between the two photosystems in the eobalt grown cells. Energy was preferentially distributed in favour of PS II accompanied by a reduction in the extent of energy transfer from PS II to PS I in cobalt-grown cells. These cells also showed a smaller PS I absorption cross-section and a smaller size of intersystem electron pool than the control cells. Thus, our results suggest that supplementation of 10 μM CoCl2, to the normal growth medium causes multiple changes involving small increase in PS II to PS I ratio, enhanced funneling of energy to PS II and an increase in PS I electron transport, decrease PS I cross section and reduction in intersystem pool size. The cumulative effects of these alterations cause stimulation in electron transport and O2 evolution.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00033123
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  • 31
    Digitale Medien
    Digitale Medien
    Can stomatal closure caused by xylem ABA explain the inhibition of leaf photosynthesis under soil drying? (1997)
    Springer
    Photosynthesis research 51 (1997), S. 149-159 
    Details
    ISSN: 1573-5079
    Schlagwort(e): abscisic acid ; t Acacia confusa ; t Leucaenaleucocephala ; photosynthesis ; soil drying ; stomatal conductance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Effects of leaf water deficit and increase in endogenous ABA on photosynthesis of two tropical trees, t Acacia confusa and t Leucaena leucocephala, were investigated with two soil-drying methods, i.e. half or whole root system was subjected to soil drying. Half-root drying was achieved by allowing upper layer of soil column to dry and lower layer of soil column to remain watered. Half-root drying had little effect on leaf water potential, but when compared to the well-watered control, both methods of soil drying substantially increased the ABA concentration in xylem and reduced leaf conductance in both species. There was a significant relationship between leaf conductance and xylem ABA concentrations in both species, which was comparable to the same relationship that was generated by feeding ABA to excised twigs. The rate of photosynthesis was inhibited substantially in both soil-drying treatments and in both species, but photochchemical efficiency, measured as a ratio of variable fluorescence to a peak fluorescence emission of a dark-adapted leaf (Fv/Fm), was not reduced except in the whole root-dried t L. leucocephala plants where leaf water potential was reduced to –2.5 MPa. In all the cases where photosynthesis was inhibited, there was a concomitant reduction in both leaf conductance and calculated internal CO2 concentration. After two days of rewatering, leaf water potential and xylem ABA concentration rapidly returned to pre-treatment levels, but leaf conductance and photosynthesis of both whole-root and half root dried t L. leucocephala remained inhibited substantially. Rewatering led to a full recovery of both stomatal conductance and photosynthesis in soil-dried t A. confusa, although its photosynthesis of whole-root dried plants did not recover fully but such difference was not significant statistically. These results suggest that drought-induced decline of photosynthesis was mainly a result of the stomatal factor caused by the increase of ABA concentration in the xylem sap. Non-stomatal factors, e.g. reduced photochemical activity and/or carbon metabolic activity, were species-specific and were brought about only at very low water potential.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005797410190
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  • 32
    Digitale Medien
    Digitale Medien
    Regulation of photosynthesis in developing leaves of soybean chlorophyll-deficient mutants (1997)
    Springer
    Photosynthesis research 51 (1997), S. 185-192 
    Details
    ISSN: 1573-5079
    Schlagwort(e): CAB ; cytochrome f ; photosynthesis ; Rubisco ; Rubisco activase ; senescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In this report we examine the factors that regulate photosynthesis during leaf ontogeny in y3y3 and Y11y11, two chlorophyll-deficient mutants of soybean. Photosynthetic rates were similar during wild type and Y11y11 leaf development, but the senescence decline in photosynthesis was accelerated in y3y3. Photosynthetic rates fell more rapidly than chlorophyll concentrations during senescence in wild type leaves, indicating that light harvesting is not strongly limiting for photosynthesis during this phase of leaf development. Chlorophyll concentrations in Y11y11, though significantly lower than normal, were able to support normal photosynthetic rates throughout leaf ontogeny. Chlorophyll a/b ratios were constant during leaf development in the wild type, but in the mutants they progressively increased (y3y3) or decreased (Y11y11). In all three sets of plants, photosynthetic rates were directly proportional to Rubisco contents and activities, suggesting that Rubisco plays a dominant role in regulating photosynthesis throughout leaf ontogeny in these plants. The expression of some photosynthetic proteins, such as Rubisco activase, was coordinately regulated with that of Rubisco in all three genotypes, i.e. an early increase, coincident with leaf expansion, followed by a senescence decline in the fully-expanded leaf. On the other hand, the light harvesting chlorophyll a/b-binding proteins of PS II (the CAB proteins), while they showed a profile similar to that of Rubisco in the wild type and y3y3, progressively increased in amount during Y11y11 leaf development. We conclude that Y11y11 may be defective in the accumulation of a component required for LHC II assembly or function, while y3y3 has more global effects and may be a regulatory factor that controls the duration of senescence.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005824706653
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  • 33
    Digitale Medien
    Digitale Medien
    Responses of three bottomland species with different flood tolerance capabilities to various flooding regimes (1996)
    Springer
    Wetlands ecology and management 4 (1996), S. 245-256 
    Details
    ISSN: 1572-9834
    Schlagwort(e): Anaerobiosis ; baldcypress ; cherrybark oak ; nuttall oak ; photosynthesis ; productivity ; soil redox potential ; stomatal conductance ; waterlogging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Seedlings of baldcypress (Taxodium distichum), nuttall oak (Quercus nuttalli), and cherrybark oak (Quercus falcata var.pagodaefolia) were subjected to four flooding treatments: control, continuously flooded, intermittently flooded, and partially flooded for 70 days in a greenhouse. The treatments imposed various durations and intensities of soil redox potential (Eh) conditions representing a range encountered by plants in their habitats. Morphological changes and gas exchange responses to the treatments differed among the study species. Rapid development of adventitious root and hypertrophied lenticels were observed in baldcypress and nuttall oak under all flooded treatments. Cherrybark oak had the highest percentage reduction in net photosynthesis ranging from 65–87%, whereas reductions in nuttall oak ranged between 35–68% and in baldcypress between 6–21% in response to various treatments. Recovery of gas exchange was noted in baldcypress but no significant recovery was found in oaks. The recovery in baldcypress contributed to the continued growth and biomass accumulation under various treatments. Little evidence of consistent changes in biomass allocation patterns in response to the treatments was found in baldcypress but total biomass decreased significantly under the continuously flooded treatment. In oaks, total biomass decreased significantly in all flooded treatments. The present findings demonstrated that physiological functions are adversely affected by low soil Eh conditions and the extent of such effects are dependent on the intensity and duration of soil reduction as well as the species' capability to respond to such conditions rapidly. Management plans concerned with regeneration of bottomland forested ecosystems should consider the species flood response capabilities at seedling stages as well as the timing, durations, and intensities of soil reduction at the specific site.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02150538
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  • 34
    Digitale Medien
    Digitale Medien
    Genetic variation in pigeon pea (Cajanus cajan (L.) Mill sp.) in response to successive cycles of water stress (1994)
    Springer
    Plant and soil 158 (1994), S. 193-201 
    Details
    ISSN: 1573-5036
    Schlagwort(e): photosynthesis ; osmotic adjustment ; stomatal conductance ; relative water content ; water potential ; water relations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Four pigeon pea [Cajanus cajan (L.) Mill sp.] cultivars were studied during two cycles of development of water stress and recovery. During these two cycles the genetic variation in vegetative development, leaf water potential, relative water content, photosynthesis, and stomatal conductance was followed. Plants were grown in a greenhouse and irrigated every seventh day. On two occasions (30 days and 80 days from sowing) water was withheld for 13 days in one group of plants and 16 days in another. Control plants were irrigated as usual. The four cultivars differed in their response to drought, with ICPL 215 being the most tolerant cultivar. In the plants exposed to the 13-day water stress, the first stress cycle resulted in preconditioning of plants such that higher values for carbon dioxide exchange rate and relative water content were observed in the second stress cycle. The longer stress period (16 days) resulted in some damage to the photosynthetic capacity and in a slow recovery rate in both cycles. During the second drought cycle the plants retained a water content above the critical value, possibly due to osmotic adjustment. It seems that water status parameters, especially relative water content, may serve as indicators of drought tolerance in pigeon pea varieties and may be useful in breeding programs for cultivation of pigeon pea under semiarid conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00009494
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  • 35
    Digitale Medien
    Digitale Medien
    Model studies of chlorophyll fluorescence reabsorption at chloroplast level under different exciting conditions (1994)
    Springer
    Photosynthesis research 40 (1994), S. 67-74 
    Details
    ISSN: 1573-5079
    Schlagwort(e): light conditions ; theoretical model ; barley leaf ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A theoretical model is presented describing the distortion of chlorophyll fluorescence spectra of a chloroplast or a group of chloroplasts by the effect of fluorescence reabsorption. Model calculations using the experimental data show that the primary reabsorption effect occurs already within one chloroplast and the spectral distortion depends significantly on the excitation regime of the chloroplast. A theoretical dependence of the distortion function, defined as a change in the F(685)/F(735) fluorescence band ratio, on the mean chlorophyll concentration in a chloroplast is predicted for different light excitation regimes. The distortion of measured chlorophyll fluorescence spectra at 77 K of chloroplast suspension adsorbed on filter papers of two strongly different diffusive reflectivities and at different mean chlorophyll concentrations are discussed with the help of the presented theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019046
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  • 36
    Digitale Medien
    Digitale Medien
    UV-B damage and protection at the molecular level in plants (1994)
    Springer
    Photosynthesis research 39 (1994), S. 475-489 
    Details
    ISSN: 1573-5079
    Schlagwort(e): DNA repair ; flavonoids ; gene expression ; oxidative stress ; photosynthesis ; promoter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Influx of solar UV-B radiation (280–320 nm) will probably increase in the future due to depletion of stratospheric ozone. In plants, there are several targets for the deleterious UV-B radiation, especially the chloroplast. This review summarizes the early effects and responses of low doses of UV-B at the molecular level. The DNA molecules of the plant cells are damaged by UV due to the formation of different photoproducts, such as pyrimidine dimers, which in turn can be combatted by specialized photoreactivating enzyme systems. In the chloroplast, the integrity of the thylakoid membrane seems to be much more sensitive than the activities of the photosynthetic components bound within. However, the decrease of mRNA transcripts for the photosynthetic complexes and other chloroplast proteins are among very early events of UV-B damage, as well as protein synthesis. Other genes, encoding defence-related enzymes, e.g., of the flavonoid biosynthetic pathway, are rapidly up-regulated after commencement of UV-B exposure. Some of the cis-acting nucleotide elements and trans-acting protein factors needed to regulate the UV-induced expression of the parsley chalcone synthase gene are known.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014600
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  • 37
    Digitale Medien
    Digitale Medien
    Photosynthetic electrogenic events in native membranes ofChloroflexus aurantiacus. Flash-induced charge displacements within the reaction center-cytochromec 554 complex (1994)
    Springer
    Photosynthesis research 41 (1994), S. 135-143 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; electrometry ; membrane potential ; electron transfer ; charge displacement ; electrostatic ; Chloroflexus aurantiacus ; Rhodopseudomonas viridis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The thermophilic phototrophChloroflexus aurantiacus possesses a photosynthetic reaction center (RC) containing a pair of menaquinones as primary (QA) and secondary (QB) electron acceptors and a bacteriochlorophyll dimer (P) as a primary donor. A tetraheme cytochromec 554 with two high(H)- and two low(L)-potential hemes operates as an immediate electron donor for P. The following equilibrium Em,7 values were determined by ESR for the hemes in whole membrane preparations: 280 mV (H1), 150 mV (H2), 95 mV (L1) and 0 mV (L2) (Van Vliet et al. (1991) Eur. J. Biochem. 199: 317–323). Partial electrogenic reactions induced by a laser flash inChl. aurantiacus chromatophores adsorbed to a phospholipid-impregnated collodion film were studied electrometrically at pH 8.3. The photoelectric response included a fast phase of ΔΨ generation (τ 〈 10 ns, phase A). It was ascribed to the charge separation between P+ and QA − as its amplitude decreased both at high and low Eh values (Em,high=360±10 mV, estimated Em,low∼\s-160 mV) in good agreement with Em values for P/P+ and QA/QA − redox couples. A slower kinetic component appeared upon reduction of the cytochromec 554 hemes (phase C). With H1 reduced before the flash the amplitude of phase C was equal to 15–20% of that of phase A and its rise time was 1.2–1.3 μs: we attribute this phase to the electrogenic electron transfer from H1 to P+. Pre-reduction of H2 decreased the τ value to about 700–800 ns and increased the amplitude of phase C to 30–35% of that of phase A. Pre-reduction of L1 further accelerated phase C (up to τ of 500 ns) and induced a reverse electrogenic phase with τ of 12 μs and amplitude equal to 10% of phase A. Upon pre-reduction of L2 the rise time of phase C was decreased to about 300 ns and its amplitude decreased by 30%. The acceleration in the onset of phase C is explained by the acceleration of the rate-limiting H1 ⇒ P electrogenic reaction after reduction of the other hemes due to their electrostatic influence; a P-H1-(L1-L2)-H2 alignment of redox centers with an approximately rhombic arrangement of the cytochromec 554 hemes is proposed. The observed reverse phase is ascribed to the post-flash charge redistribution between the hemes. Redox titration of the amplitude of phase C yielded the Em,8.3 values of H1, H2 and L2 hemes: 340±10 mV for H1, 160±20 mV for H2 and −40±40 mV for L2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184153
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  • 38
    Digitale Medien
    Digitale Medien
    Pigment interactions in chlorosomes of various green bacteria (1994)
    Springer
    Photosynthesis research 41 (1994), S. 175-180 
    Details
    ISSN: 1573-5079
    Schlagwort(e): Chlorobium ; Chloroflexus ; chlorophyll ; light-harvesting ; photosynthesis ; resonance Raman
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Resonance Raman experiments were performed on different green bacteria. With blue excitation, i.e. under Soret resonance or preresonance conditions, resonance Raman contributions were essentially arising from the chlorosome pigments. By comparing these spectra and those of isolated chlorosomes, it is possible to evaluate how the latter retain their native structure during the isolation procedures. The structure of bacteriochlorophyll oligomers in chlorosomes was interspecifically compared, in bacteriochlorophyllc- and bacteriochlorophylle- synthesising bacteria. It appears that interactions assumed by the 9-keto carbonyl group are identical inChlorobium limicola, Chlorobium tepidum, andChlorobium phaeobacteroides. In the latter strain, the 3-formyl carbonyl group of bacteriochlorophylle is kept free from intermolecular interactions. By contrast, resonance Raman spectra unambiguously indicate that the structure of bacteriochlorophyll oligomers is slightly different in chlorosomes fromChloroflexus auranticus, either isolated or in the whole bacteria.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184158
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  • 39
    Digitale Medien
    Digitale Medien
    The formation and characterization of the in vitro polymeric aggregates of bacteriochlorophyllc homologs fromChlorobium limicola in aqueous suspension in the presence of monogalactosyl diglyceride (1994)
    Springer
    Photosynthesis research 41 (1994), S. 235-243 
    Details
    ISSN: 1573-5079
    Schlagwort(e): bacteriochlorophyll ; chlorosomeChlorobium limicola ; green bacteria ; photosynthesis ; monogalactosyl diglyceride
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Artificial aggregates of bacteriochlorophyllc (BChlc) were formed in an aqueous medium in the presence of a lipid, monogalactosyl diglyceride (MGDG), and the optical properties of those aggregates were studied by absorption and circular dichroism (CD) mainly. Four BChlc homologs, ([E,E]BChlc F, [P,E]BChlc F, [E,M]BChlc F and [I,E]BChlc F), were isolated from the green photosynthetic bacteriumChlorobium limicola strain 6230. Above 0.0004%, MGDG induced a red-shift of the absorption maxima of BChlc aggregates. At 0.003% MGDG BChlc aggregates showed absorption maxima in the range of 724 to 745 (±3) nm with a shift of 12 to 24 (±3) nm depending on the homolog species. Four kinds of BChlc-MGDG aggregates showed characteristic CD spectra. [E,M]BChlc F gave rise to a CD spectrum similar to that of chlorosomes, while the other three gave spectra of opposite sign. These aggregates are sensitive to 1-hexanol treatment; in a saturating amount (0.85%) of 1-hexanol, all the homologs gave a monomer-like absorption spectrum peaking at 670nm. At an intermediate concentration (0.5%), [E,M]BChlc F showed an enhanced CD intensity, as observed in native chlorosomes. Resonance Raman spectra of the monomer-like BChlc samples indicated that the keto vibrational band at ca. 1640 cm−1 was considerably weakened by the 0.85% 1-hexanol treatment, however the 1680 cm−1 band characteristic of a free keto group did not appear. These results indicate that the artificial aggregates formed by purified BChlc homologs and MGDG are good models for studying chlorosomes structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184164
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  • 40
    Digitale Medien
    Digitale Medien
    Sensitivity of the relative Fpl level of chlorophyll fluorescence induction in leaves to the heat stress (1994)
    Springer
    Photosynthesis research 39 (1994), S. 201-204 
    Details
    ISSN: 1573-5079
    Schlagwort(e): automatic determination ; fluorescence parameters ; fluorometer ; induction curve ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The (Fpl-Fo)/Fv value of the fluorescence induction curve is shown to be a more suitable parameter to detect a wider range of heat stress damage to thylakoid membranes as compared to quantities t 1/2 (time of fluorescence rise from Fo to (Fo+Fm)/2 level) and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaWaa0aaaeaacq% aHepaDaaaaaa!39D5!\[\overline \tau \] (the fluorescence induction time defined as the area above the induction curve normalized to Fv=1). A method for exact and automatic Fpl determination is presented. A break point in the quality and behaviour of the fluorescence induction curve of barley leaves incubated at 49°C was reached at the moment (about 240 s) when the transformation of PS II active (QB-reducing) to PS II inactive (QB-non-reducing) centres was completed. The meaning of the standard Fv and Fv/Fm parameter was then changed. The method of Fpl determination described here may help to increase the analytical value of the standard chlorophyll fluorometers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029387
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  • 41
    Digitale Medien
    Digitale Medien
    The role of iron in phytoplankton photosynthesis, and the potential for iron-limitation of primary productivity in the sea (1994)
    Springer
    Photosynthesis research 39 (1994), S. 275-301 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorosis ; diagnostic ; flavodoxin ; iron-limitation ; photosynthesis ; phytoplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Iron supply has been suggested to influence phytoplankton biomass, growth rate and species composition, as well as primary productivity in both high and low NO3 − surface waters. Recent investigations in the equatorial Pacific suggest that no single factor regulates primary productivity. Rather, an interplay of bottom-up (i.e., ecophysiological) and top-down (i.e., ecological) factors appear to control species composition and growth rates. One goal of biological oceanography is to isolate the effects of single factors from this multiplicity of interactions, and to identify the factors with a disproportionate impact. Unfortunately, our tools, with several notable exceptions, have been largely inadequate to the task. In particular, the standard technique of nutrient addition bioassays cannot be undertaken without introducing artifacts. These so-called ‘bottle effects’ include reducing turbulence, isolating the enclosed sample from nutrient resupply and grazing, trapping the isolated sample at a fixed position within the water column and thus removing it from vertical movement through a light gradient, and exposing the sample to potentially stimulatory or inhibitory substances on the enclosure walls. The problem faced by all users of enrichment experiments is to separate the effects of controlled nutrient additions from uncontrolled changes in other environmental and ecological factors. To overcome these limitations, oceanographers have sought physiological or molecular indices to diagnose nutrient limitation in natural samples. These indices are often based on reductions in the abundance of photosynthetic and other catalysts, or on changes in the efficiency of these catalysts. Reductions in photosynthetic efficiency often accompany nutrient limitation either because of accumulation of damage, or impairment of the ability to synthesize fully functional macromolecular assemblages. Many catalysts involved in electron transfer and reductive biosyntheses contain iron, and the abundances of most of these catalysts decline under iron-limited conditions. Reductions of ferredoxin or cytochrome f content, nitrate assimilation rates, and dinitrogen fixation rates are amongst the diagnostics that have been used to infer iron limitation in some marine systems. An alternative approach to diagnosing iron-limitation uses molecules whose abundance increases in response to iron-limitation. These include cell surface iron-transport proteins, and the electron transfer protein flavodoxin which replaces the Fe-S protein ferredoxin in many Fe-deficient algae and cyanobacteria.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014588
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  • 42
    Digitale Medien
    Digitale Medien
    Molecular topology of the Photosystem II chlorophyll a binding protein, CP 43: Topology of a thylakoid membrane protein (1994)
    Springer
    Photosynthesis research 40 (1994), S. 11-19 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; membrane protein ; protein structure ; light harvesting
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have used antibodies generated against synthetic peptides to determine the topology of the 43 kD chlorophyll a binding protein (CP 43) of Photosystem II. Based on the pattern of proteolytic fragments detected (on western blots) by peptide specific antibodies, a six transmembrane span topological model, with the amino and carboxyl termini located on the stromal membrane surface, is predicted. This structure is similar to that predicted for CP 47, a PS II chlorophyll a binding protein (Bricker T (1990) Photosynth Res 24: 1–13). The model is discussed in reference to the possible location of chlorophyll binding sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019041
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  • 43
    Digitale Medien
    Digitale Medien
    The Wageningen Rhizolab — a facility to study soil-root-shoot-atmosphere interactions in crops (1994)
    Springer
    Plant and soil 161 (1994), S. 275-287 
    Details
    ISSN: 1573-5036
    Schlagwort(e): crop growth ; gas exchange ; minirhizotrons ; nutrients ; photosynthesis ; respiration ; rhizotron ; root observation ; root growth ; water balance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A research facility is described for the integrated study of soil-root-shoot-atmosphere relationships in crops. The Wageningen Rhizolab has been in use since 1990, and consists of two rows, each with eight below-ground compartments aligned along a corridor. A rain shelter automatically covers the experimental area at the start of rainfall. Compartments are 125 cm × 125 cm and 200 cm deep. Each compartment has a separate drip irrigation system. Crop canopy photosynthesis, respiration, and transpiration can be measured simultaneously and continuously on four out of eight compartments at a time. Each compartment can be filled with a selected soil material (repacked soil) and is accessible from the corridor over its full depth. Multiple sensors for measuring soil moisture status, electrical conductivity, temperature, soil respiration, trace gases and oxygen are installed in spatial patterns in accordance with the requirements of the experiments. Sensors are connected to control and data-acquisition devices. Likewise, provisions have been made to sample manually the soil solution and soil atmosphere. Root observation tubes (minirhizotrons) are installed horizontally at depth intervals ranging from 5 cm (upper soil layers) to 25 cm (below 1 m). The facility is at present in use to study growth and development of vegetation (crops) in relation to drought, nutrient status, soil-borne diseases, and underground root competition. One important application is the study of elevated CO2 concentration and climate change and the way they affect crops and their carbon economy. Growth and development of field grown vegetables and winter cover crops are also evaluated. The common aspect of those studies is to gain a better understanding of crop growth under varying environmental conditions, and to collect datasets that may help to improve mechanistic crop growth simulation models that can address suboptimal growth conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00046399
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  • 44
    Digitale Medien
    Digitale Medien
    Measurement and modelling of photosynthetic response of pearl millet to soil phosphorus addition (1996)
    Springer
    Plant and soil 184 (1996), S. 67-73 
    Details
    ISSN: 1573-5036
    Schlagwort(e): pearl millet ; Pennisetum glaucum (L.) R. Br. ; phosphorus ; photosynthesis ; modelling
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract There have been no studies of the effects of soil P deficiency on pearl millet (Pennisetum glaucum (L.) R. Br.) photosynthesis, despite the fact that P deficiency is the major constraint to pearl millet production in most regions of West Africa. Because current photosynthesis-based crop simulation models do not explicitly take into account P deficiency effects on leaf photosynthesis, they cannot predict millet growth without extensive calibration. We studied the effects of soil addition on leaf P content, photosynthetic rate (A), and whole-plant dry matter production (DM) of non-water-stressed, 28 d pearl millet plants grown in pots containing 6.00 kg of a P-deficient soil. As soil P addition increased from 0 to 155.2 mg P kg−1 soil, leaf P content increased from 0.65 to 7.0 g kg−1. Both A and DM had maximal values near 51.7 mg P kg−1 soil, which corresponded to a leaf P content of 3.2 g kg−1. Within this range of soil P addition, the slope of A plotted against stomatal conductance (gs) tripled, and mean leaf internal CO2 concentration ([CO2]i) decreased from 260 to 92 μL L−1, thus indicating that P deficiency limited A through metabolic dysfunction rather than stomatal regulation. Light response curves of A, which changed markedly with P leaf content, were modelled as a single substrate, Michaelis-Menten reaction, using quantum flux as the substrate for each level of soil P addition. An Eadie-Hofstee plot of light response data revealed that both KM, which is mathematically equivalent to quantum efficiency, and Vmax, which is the light-saturated rate of photosynthesis, increased sharply from leaf P contents of 0.6 to 3 g kg−1, with peak values between 4 and 5 g P kg−1. Polynomial equations relating KM and Vmax, to leaf P content offered a simple and attractive way of modelling photosynthetic light response for plants of different P status, but this approach is somewhat complicated by the decrease of leaf P content with ontogeny.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029275
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  • 45
    Digitale Medien
    Digitale Medien
    Abscisic acid concentrations are correlated with leaf area reductions in two salt-stressed rapid-cycling Brassica species (1996)
    Springer
    Plant and soil 179 (1996), S. 25-33 
    Details
    ISSN: 1573-5036
    Schlagwort(e): abscisic acid ; Brassica napus ; Brassica carinata ; callus ; photosynthesis ; plant growth ; salinity ; salt tolerance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The greater sensitivity of B. carinata to salinity in comparison to B. napus has been linked to a greater reduction in net assimilation rate. Apparently this is not due to ion toxicity; the cause is unknown. In this report, we test the hypothesis that increases in abscisic acid (ABA) are involved in the reduction of growth by salinity. Salinity (8 dS m−1) caused an increase of ABA concentrations in the shoot, root and callus of both species. ABA concentrations were lower in the salt-tolerant species, B. napus, than the salt-sensitive species, B. carinata, both in the whole plant and callus. Leaf expansion for both species was equally sensitive to ABA; salt stress did not significantly alter sensitivity to applied ABA. The growth inhibition increased in a hyperbolic manner with an increase in endogenous ABA concentration. These results indicate that ABA in salt-stressed plants may play a role in the inhibition of growth. The photosynthesis of salt-sensitive species, B. carinata, was also decreased by salinity, corresponding to the reduction in growth. The decreased photosynthesis does not appear to be the cause of the growth reduction, because photosynthesis was not inhibited by short-term exposure to salinity and photosynthesis was poorly correlated with endogenous ABA concentrations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00011639
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  • 46
    Digitale Medien
    Digitale Medien
    Biomass accumulation and allocation in soybean associated with genotypic differences in tolerance of nitrogen fixation to water deficits (1997)
    Springer
    Plant and soil 196 (1997), S. 101-113 
    Details
    ISSN: 1573-5036
    Schlagwort(e): drought ; Glycine max ; photosynthesis ; water use efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Nitrogen fixation in soybean (Glycine max [L.] Merr.) is more sensitive to water deficits than many physiological processes and may therefore limit yield under nonirrigated conditions. Tolerance of nitrogen fixation to water deficits has been observed in the cultivar Jackson, however, the physiological basis for this is unclear. It was hypothesized that genotypes that could continue biomass production on limited soil water would prolong nitrogen fixation by continued photosynthate allocation to nodules. An initial greenhouse experiment compared biomass and N accumulation in six genotypes over an 8 d water deficit. Low stress intensity minimized genotypic expression of water-deficit tolerance; nevertheless, Jackson was clearly one of the most tolerant genotypes. In a second experiment, Jackson was compared to SCE82-303 at more severe stress levels. Biomass and N accumulation continued during water deficits for Jackson but ceased in SCE82-303. Individual nodule mass tended to increase during water deficits in Jackson and tended to decrease in SCE82-303, indicating greater allocation of photosynthate to Jackson's nodules in response to water deficits. Biomass accumulation of Jackson was contrasted with the USDA plant introduction (PI) 416937, which also has demonstrated tolerance to water deficits. For water-deficit treatments, total biomass accumulation was negligible for PI416937, but biomass accumulation continued at approximately 64% of the control treatment for Jackson. Transpirational losses for Jackson and PI416937 were approximately the same for the water-deficit treatment, indicating that Jackson had higher water use efficiency (WUE). Isotopic discrimination of 13C relative to12 C also indicated that Jackson had superior WUE during water deficits. Carbon-14 allocation in Jackson was compared to KS4895, a cultivar that was identified as sensitive to water deficits in an initial experiment. The comparison of water-deficit treatments of Jackson with KS4895 indicated that Jackson exported significantly greater amounts of14 C from labeled leaves and allocated approximately four times greater amounts of 14C per g of nodule. Results indicated that Jackson's sustained biomass production during water deficits resulted in the continued allocation of photosynthate to nodules and prolonged nitrogenase activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004289609466
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  • 47
    Digitale Medien
    Digitale Medien
    Does boron play only a structural role in the growing tissues of higher plants? (1997)
    Springer
    Plant and soil 196 (1997), S. 211-215 
    Details
    ISSN: 1573-5036
    Schlagwort(e): boron ; deficiency ; function ; membrane ; mobility ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In species in which boron (B) mobility is limited, B deficiency only occurs in growing plant organs. As a consequence of the highly localized patterns of plant growth and the general immobility of B it has been extremely difficult to determine the primary function of B in plants. In species in which B is phloem mobile, the removal of B from the growth medium results in the depletion of B present in mature leaves. Thus, it is possible to develop mature leaves with increasingly severe levels of B depletion, thereby overcoming the complications of experiments based on growing tissues. Utilizing this approach we demonstrate here that B depletion of mature plum (Prunus salicina) leaves did not result in any discernible change in leaf appearance, membrane integrity or photosynthetic capacity even though B concentrations were reduced to 6-8 µg/g dwt, which is less than 30% of the reported tissue B requirement. Boron depletion, however, results in a severe disruption of plant growth and metabolism in young growing tissues. This experimental evidence and theoretical considerations suggest that the primary and possibly sole function of B, is as a structural component of growing tissues.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004245823080
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  • 48
    Digitale Medien
    Digitale Medien
    Effects of nitrogen supply on the acclimation of photosynthesis to elevated CO2 (1994)
    Springer
    Photosynthesis research 39 (1994), S. 389-400 
    Details
    ISSN: 1573-5079
    Schlagwort(e): elevated CO2 ; nitrogen supply ; photosynthesis ; acclimation ; growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A common observation in plants grown in elevated CO2 concentration is that the rate of photosynthesis is lower than expected from the dependence of photosynthesis upon CO2 concentration in single leaves of plants grown at present CO2 concentration. Furthermore, it has been suggested that this apparent down regulation of photosynthesis may be larger in leaves of plants at low nitrogen supply than at higher nitrogen supply. However, the available data are rather limited and contradictory. In this paper, particular attention is drawn to the way in which whole plant growth response to N supply constitutes a variable sink strength for carbohydrate usage and how this may affect photosynthesis. The need for further studies of the acclimation of photosynthesis at elevated CO2 in leaves of plants whose N supply has resulted in well-defined growth rate and sink activity is emphasised, and brief consideration is made of how this might be achieved.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014593
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  • 49
    Digitale Medien
    Digitale Medien
    Effect of genome and ploidy on photosynthesis of wheat (1997)
    Springer
    Euphytica 94 (1997), S. 303-309 
    Details
    ISSN: 1573-5060
    Schlagwort(e): photosynthesis ; hexaploid wheat ; A genome ; D genome ; polyploidy ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We assessed (1) the effects of addition and doses of the D genome from different sources and (2) the addition of either the A genome or the D genome on the photosynthesis of synthesized hexaploid wheats. On average, the increased doses of the D genome reduced photosynthesis, but the depression was dependent on the source of the D genome. Two accessions of Aegilops squarrosa had depressed photosynthetic rates, but not another accession of Ae. squarrosa. The D genome of cv. Thatcher did not contribute to depress photosynthetic rate. Triticum monococcum had considerably higher photosynthetic rates than Ae. squarrosa. However, addition of the A genome from T. monococcum did not increase the photosynthetic rates of hexaploids. Chlorophyll a : b ratio, functional photosystem II and the core complex of photosystem II did not account for the variation in photosynthetic rate among the genotypes studied. In our experiment, photosynthesis of polyploids was not dependent on photosynthesis rates of the donor genomes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1002936019332
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  • 50
    Digitale Medien
    Digitale Medien
    Oceanic picophytoplankton having a high abundance of chlorophyll b in the major light harvesting chlorophyll protein complex (1997)
    Springer
    Photosynthesis research 53 (1997), S. 121-127 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll a/b light-harvesting complex ; major LHCP ; oceanic picophytoplankton ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chl a-containing, very small unicellular, eukaryotic phytoplankton (picophytoplankton) often become the dominant organisms near the bottom of the euphotic zone in the ocean, where light is limited, not only in intensity (about 0.5% of the surface irradiance), but also in quality (dominant in blue to green wavelengths). We have isolated picophytoplankton from subsurface waters (from 75 to 150 m in depth) of the Kuroshio area near Japan. EM observations showed that a single chloroplast occupies a large part of the cytoplasm. Some of the isolates have a flagellum. The major photosynthetic pigments found in these isolates were chlorophyll a and b. The light-harvesting chlorophyll a/b complex (LHCP) was isolated from three clones of picophytoplankton, one flagellated form (NIBB8001) and two coccoid forms (94B8100A and 94B5100C) . More than 50% of the total chlorophylls were recovered in the major LHCP fraction. A common feature of the major LHCPs isolated from the three picophytoplankton clones was a high abundance of chlorophyll b: the ratios of chlorophyll a to b were about 0.8, 0.7 and 0.6 for the clones NIBB8001, 94B8100A and 94B5100C, respectively. These values were very low compared with those in chlorophyll a/b-binding LHCIIs in higher plants and in the major chlorophyll a/b-binding LHCPs in microalgae (higher than 1.0). The major LHCP apoproteins of NIBB8001 and 94B5100C contained one major polypeptide; the apparent molecular masses analyzed with SDS-PAGE were about 22 kDa and 27 kDa, respectively. The major LHCP apoprotein of 94B8100A had two major polypeptides having apparent molecular masses of about 23 and 25 kDa. None of the thylakoid proteins cross-reacted with an antibody raised against the LHC IIα apoprotein of spinach. It is suggested that the high abundance of chlorophyll b in picophytoplankton, together with a large chloroplast in a small cell, enable them to utilize the reduced light in their habitat.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005857903821
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  • 51
    Digitale Medien
    Digitale Medien
    Chromophore assignment in phycoerythrocyanin from Mastigocladus laminosus (1997)
    Springer
    Photosynthesis research 54 (1997), S. 25-34 
    Details
    ISSN: 1573-5079
    Schlagwort(e): cyanobacteria ; energy transfer ; Fischerella PCC 7603 ; photosynthesis ; phycobiliprotein ; phycoerythrocyanin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The component spectra (maxima of absorption, circular and linear dichroism) of individual chromophores have been assigned for phycoerythrocyanin (PEC) trimer, monomer(s), and its subunits (α-PEC and β-PEC) by titration with p-chloromercury-benzene-sulfonate (PCMS), linear dichroism and photochemical transformations, as well as by deconvolution using a ‘bilin’ line-shape spectrum based on the α-84 phycoviolobilin-chromophore in the α-subunit. The level ordering PVB-α-84 → PCB-β-155 → PCB-β-84 is the same irrespective of aggregation. Two different monomers (αβ) were observed. In 4 M urea, the spectra are appropriately weighted sums of the subunit spectra, whereas in the monomer obtained in 1 M KSCN, both β-chromophores are red-shifted by 4–5 nm. Formation of trimer (αβ)_3gives considerable spectral changes: (1) the absorption is narrowed, which has been rationalized by excitonic coupling between neighbouring monomers, (2) the short wavelength part in the CD spectrum is missing and (3) a fourth band (+) at 528 in the LD spectrum appears. A deconvolution of the trimeric aggregation state using only the ‘bilin’ line-shape model is not possible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005877531271
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  • 52
    Digitale Medien
    Digitale Medien
    Characterisation of cytochrome c6from Chlorella fusca (1997)
    Springer
    Photosynthesis research 54 (1997), S. 107-114 
    Details
    ISSN: 1573-5079
    Schlagwort(e): CD ; Chlorella ; cytochrome c6 ; EPR ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A c-type monohaem, cytochrome c6was isolated from a soluble extract of the green alga Chlorella fusca. The isolated protein shows an apparent molecular mass of 10 kDa by SDS-PAGE, but behaves as a dimer of 20.3 kDa in gel-filtration; the isoelectric point is 3.6. The N-terminal sequence shows high identity with other green algae cytochromes c6. The mid-point redox potential is about +350 mV between pH 5 and 9. The ferric and ferrous forms, and their pH equilibria, have been studied using visible, CD and EPR spectroscopies. The visible spectrum of the reduced cytochrome c6is typical of a c-type haem protein, with maxima at 274 nm, 318 nm (δ-peak), 416 nm (γ-peak), 522 nm (β-peak), 552–553 nm (α-peak). A 690 nm band, characteristic of a haem Met-His axial coordination of the haem group, is present in the oxidized form. At high pH values (≥ 8), cytochrome c6undergoes an alkaline transition, with a pKa of 8.7. Between pH 3 and 9 the EPR spectrum is dominated by two rhombic species, with g-values at 3.32, 2.05, 1.05 and 2.96, 2.30, 1.43, which interconvert with a pKaof 4. CD spectrum of Chlorella fusca cytochrome c6shows that the proteins must be mainly built up by α-helices. Even though there are similarities between Chlorella fusca cytochrome c6and that isolated from Monoraphidium braunii, no cross-reactivity with the antibodies raised against the Chlorella fusca cytochrome has been detected for the protein from Monoraphidium braunii.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005955201482
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  • 53
    Digitale Medien
    Digitale Medien
    The effects of elevated light on Photosystem II function: A thermoluminescence study (1997)
    Springer
    Photosynthesis research 54 (1997), S. 169-183 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll fluorescence quenching ; photoinhibition ; photoprotection ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have used the technique of thermoluminescence (TL) to investigate high-light-induced chlorophyll fluorescence quenching phenomena in barley leaves, and have shown it to be a powerful tool in such investigations. TL measurements were taken from wild-type and chlorina f2 barley leaves which had been dark-adapted or exposed to 20 min illumination of varying irradiance or given varying periods of recovery following strong irradiance. We have found strong evidence that there is a sustained trans-thylakoid ΔpH in leaves following illumination, and that this ΔpH gives rise to quenching of chlorophyll fluorescence which has previously been identified as a slowly-relaxing component of antenna-related protective energy dissipation; we have identified a state of the PS II reaction centre resulting from high light treatments which is apparently able to perform normal charge separation and electron transport but which is ‘non-photochemically’ quenched, in that the application of a light pulse of high irradiance cannot cause the formation of a high fluorescent state; and we have provided evidence that a transient state of the PS II reaction centre is formed during recovery from such high light treatments, in which electron transport from QAto QBis apparently impaired.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005969312448
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  • 54
    Digitale Medien
    Digitale Medien
    The modification of phytosterol profiles and in vitro photosynthetic electron transport of Galium aparine L. (cleavers) treated with the fungicide, epoxiconazole (1997)
    Springer
    Plant growth regulation 22 (1997), S. 93-100 
    Details
    ISSN: 1573-5087
    Schlagwort(e): epoxiconazole ; Galium aparine L. ; photosynthesis ; phytosterols ; thylakoid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Foliar application of the triazole fungicide, epoxiconazole, retarded the growth of Galium aparine L. (cleavers). GC-MS and GC analysis clearly indicated that phytosterol biosynthesis in stem and leaflet tissue was significantly affected by this treatment. For example, in leaflet tissues, 125 g ai ha-1 (field rate) caused reductions in campesterol and sitosterol of 81percnt; and 75percnt; respectively. C14-methyl phytosterols such as 14agr;-methylergost-8-enol, obtusifoliol and dihydroobtusifoliol were detected in treated tissues indicating that epoxiconazole inhibits the cytochrome P-450 dependent obtusifoliol 14agr;-demethylase. In addition, ratios of campesterol to sitosterol were reduced. Stigmasterol was not detected in control or treated tissues. Preliminary determination of photosynthetic characteristics of isolated thylakoids from treated plants indicated that electron transport and oxygen evolution were impaired by epoxiconazole and these effects were dose-related. Ten days after treatment, oxygen evolution from thylakoids (determined as electron flow from water to ferricyanide) isolated from control plants was 24.2 micro;mol mg-1 chl h-1, whilst treatment with 125 g and 250 g ai ha-1 reduced this rate to 15.2 micro;mol and 8.2 micro;mol mg-1 chl h-1 an inhibition of 37 and 67percnt; respectively. These results suggest that epoxiconazole influences thylakoid integrity and function in addition to phytosterol biosynthesis in G. aparine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005885312748
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  • 55
    Digitale Medien
    Digitale Medien
    The dependance of root growth potential on light level, photosynthetic rate, and root starch content in jack pine seedlings (1997)
    Springer
    New forests 13 (1997), S. 105-119 
    Details
    ISSN: 1573-5095
    Schlagwort(e): field performance potential ; photosynthesis ; Pinus banksiana ; root initiation ; root starch ; seedling testing ; total nonstructural carbohydrates
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Number of new roots (root growth potential or RGP), new root length, photosynthesis, total nonstructural carbohydrate content of needles and roots, terminal bud condition, and shoot elongation were measured on jack pine container seedlings for 4 weeks at weekly intervals under greenhouse conditions of 100%, 20%, and 10% sunlight to simulate competition-induced, lower light levels in the field. Both lower light levels significantly reduced photosynthetic rate, RGP, new root length, total nonstructural carbohydrate (especially starch) content of needles and roots, speed of terminal bud flush, and shoot growth. Both light level and photosynthetic rate were positively correlated with RGP and new root length, indicating that jack pine seedlings may use current photosynthate as an energy source to support new root growth. RGP and new root length were also both negatively correlated with root starch content suggesting that jack pine seedlings may also use stored carbohydrates as a potential carbon source for root initiation and initial root growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006517820981
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  • 56
    Digitale Medien
    Digitale Medien
    The influence of ammonia on the growth and photosynthesis of Ruppia drepanensis Tineo from Doñana National Park (SW Spain) (1994)
    Springer
    Hydrobiologia 275-276 (1994), S. 219-231 
    Details
    ISSN: 1573-5117
    Schlagwort(e): Ruppia drepanensis ; ammonia toxicity ; temperature effects ; photosynthesis ; growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In a laboratory experiment, Ruppia drepanensis Tineo seedlings from a brackish marsh in Southern Spain were grown at 20 and 30 °C, at three different nitrogen levels. These levels were obtained by the addition of a slow release fertilizer (23% NH4NO3 by weight) to a sediment mixture of sand and clay (3:1). Several morphometric parameters were recorded during the first five weeks of the experiment, and photosynthesis and respiration were measured after 7 weeks of growth. Results showed a significant reduction of growth and development with increasing nitrogen and temperature levels. Dark respiration increased strongly at high nitrogen levels. At the same time, net photosynthesis at 250 and 500 µE m-2 s-1, Pm, Km and LCP were not affected by either factor. We attribute these phenomena to ammonia toxicity, since relatively high total ammonia (NH3 + NHf4 p+) levels were found in the interstitial water.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00026713
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  • 57
    Digitale Medien
    Digitale Medien
    Chlorophyll fluorescence as an indicator of frost hardiness in white spruce seedlings from different latitudes (1996)
    Springer
    New forests 11 (1996), S. 233-253 
    Details
    ISSN: 1573-5095
    Schlagwort(e): variable chlorophyll fluorescence ; frost hardiness ; freezing damage ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This study examined the utility of variable chlorophyll fluorescence (Fvar) to detect freezing damage in white spruce seedlings of four seedlots. Logistic regression analysis done for freezing tests in September showed that visible needle damage from freezing could be estimated by the Fvar attributes Fo/IABS(r2=0.94), Fp(r2=0.98), Fv/Fm (r2=0.99), and F1(r2=0.86). The regression curves indicated that for all four fluorescence attributes, inflection points occurred between 10 and 20% visible needle damage. The lack of a relationship between fluorescence attributes and visible seedling needle damage in October through December is because the minimum temperature (−18 and −24°C respectively) applied was insufficient to cause needle damage. Freezing-induced changes to Fvar attributes can be detected which also result in photosynthetic rate decreases when no visible needle damage, and even electrolyte conductivity changes are evident. Fvar attribute differences due to freezing can be resolved to the seedlot level. The Fvar curve feature manifested 5 seconds after dark-adapted seedlings have been exposed to light (F5s) will estimate (r2=0.76) photosynthetic rate after freezing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00036784
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  • 58
    Digitale Medien
    Digitale Medien
    Environmental control of phytoplankton productivity in turbulent turbid systems (1994)
    Springer
    Hydrobiologia 289 (1994), S. 65-72 
    Details
    ISSN: 1573-5117
    Schlagwort(e): photosynthesis ; selective environments ; resuspension ; disturbance ; rivers ; shallow lakes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Factors affecting phytoplankton productivity are analysed in turbid systems, such as shallow lakes and rivers. When resuspension from the sediment or loading from the catchment significantly increases inorganic (non-algal) turbidity and hence light attenuation potentials for high production are not realised. Energy available for phytoplankton growth is strongly regulated by underwater light availability which depends on the critical mixing depth, fluctuating light intensities and algal circulation patterns. Higher production rates in shallow waters are often compensated by greater algal respiration due to higher water temperatures when compared to deeper lakes. Total daily integral production of turbulent, turbid environments can be predicted from a combination of easily measured variables such as maximum photosynthetic rates, algal biomass, surface irradiance and some measure of underwater light attenuation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00007409
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  • 59
    Digitale Medien
    Digitale Medien
    The mechanism of the degradation of psaB gene product, one of the photosynthetic reaction center subunits of Photosystem I, upon photoinhibition (1997)
    Springer
    Photosynthesis research 53 (1997), S. 55-63 
    Details
    ISSN: 1573-5079
    Schlagwort(e): hydroxyl radical ; light stress ; photosynthesis ; serine protease ; protein turnover ; reactive oxygen species
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The psaB gene product (PsaB protein), one of the reaction center subunits of Photosystem I (PS I), was specifically degraded by light illumination of spinach thylakoid membranes. The degradation of the protein yielded N-terminal fragments of molecular mass 51 kDa and 45 kDa. The formation of the 51 kDa fragment was i) partially suppressed by the addition of phenylmethylsulfonyl fluoride or 3,4-dichloroisocoumarin, which are inhibitors of serine proteases, and ii) enhanced in the presence of hydrogen peroxide during photoinhibitory treatment, but iii) not detected following hydrogen peroxide treatment in the dark. These results suggest that the hydroxyl radical produced at the reduced iron-sulfur centers in PS I triggers the conformational change of the PS I complex, which allows access of a serine-type protease to PsaB. This results in the formation of the 51 kDa N-terminal fragment, presumably by cleavage on the loop exposed to the stromal side, between putative helices 8 and 9. On the other hand, the formation of the 45 kDa fragment, which was enhanced in the presence of methyl viologen but did not accompany the photoinhibition of PS I, was not affected by the addition of hydrogen peroxide or protease inhibitors. Another fragment of 18 kDa was identified as a C-terminal counterpart of the 45 kDa fragment. N-terminal sequence analysis of the 18 kDa fragment revealed that the cleavage occurred between Ala500 and Val501 on the loop exposed to the lumenal side, between putative helices 7 and 8 of the PsaB protein.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005852330671
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  • 60
    Digitale Medien
    Digitale Medien
    Effects of homobrassinolide application on plant metabolism and grain yield under irrigated and moisture-stress conditions of two wheat varieties (1994)
    Springer
    Plant growth regulation 14 (1994), S. 173-181 
    Details
    ISSN: 1573-5087
    Schlagwort(e): homobrassinolide ; irrigated ; membrane stability ; moisture-stress ; nitrate reductase activity ; photosynthesis ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Homobrassinolide (BR) was applied either as a seed treatment or foliar spray to two contrasting wheat varieties, viz. C306 (drought tolerant) and HD2329 (drought susceptible), to examine its effects on plant metabolism and grain yield under irrigated and moisture-stress/rainfed conditions. BR application resulted in increased relative water content, nitrate reductase activity, chlorophyll content and photosynthesis under both conditions. BR application also improved membrane stability (lower injury). These beneficial effects resulted in higher leaf area, biomass production, grain yield and yield related parameters in the treated plants. All the treatments were significantly better than the untreated control. Generally, 0.05 ppm either as a seed treatment or foliar spray was more effective than the 0.01 ppm treatment. The drought-tolerant genotype C306 showed more response to BR application under moisture-stress/rainfed condition than HD 2329. Increased water uptake, membrane stability and higher carbon dioxide and nitrogen assimilation rates under stress seemed to be related to homobrassinolide-induced drought tolerance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00025220
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  • 61
    Digitale Medien
    Digitale Medien
    Development and ecological importance of phytoplankton in a large lowland river (River Meuse, Belgium) (1994)
    Springer
    Hydrobiologia 289 (1994), S. 139-155 
    Details
    ISSN: 1573-5117
    Schlagwort(e): potamoplankton ; regulated river ; transport of carbon and nutrients ; photosynthesis ; respiration ; dynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The ecological importance of the River Meuse phytoplankton with regard to carbon and nutrient transport has been examined in two reaches of the Belgian course of the river. Field measurements of total particulate organic carbon (POC), particulate organic nitrogen (PON) and particulate phosphorus (PP) show that the large autochtonous production of organic matter strongly affects the carbon and nutrient budget of the aquatic system. During the growing season, phytoplankton accounts for nearly 60% of the POC and dominates the PON. Calculations of the carbon and oxygen budget in the upper reach of the Belgian Meuse demonstrates that the ecosystem is autotrophic, i.e. that autochtonous FPOM (fine particulate organic matter) production is the major carbon input. This suggests that in large lowland rivers, primary production (P) may exceed community respiration (R), i.e. P:R〉1, whereas they are assumed to be heterotrophic (P:R〈1) in the River Continuum concept. The question of maintenance of phytoplankton in turbid mixed water columns is also addressed, and the case of the River Meuse is treated on the basis of studies of photosynthesis and respiration (ETS measurements). The results suggest that the potamoplankton may show some low-light acclimation, through an increase of chlorophyll a relative to biomass, when it comes to deep downstream reaches, and that algal respiration rate may be reduced. A simulation of the longitudinal development of the algal biomass shows the different phases of algal growth and decline along the river and brings support to the ‘importation hypothesis’ for explaining maintenance of potamoplankton in the downstream reaches.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00007415
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  • 62
    Digitale Medien
    Digitale Medien
    An active Mehler-peroxidase reaction sequence can prevent cyclic PS I electron transport in the presence of dioxygen in intact spinach chloroplasts (1994)
    Springer
    Photosynthesis research 41 (1994), S. 429-437 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; ascorbate peroxidase ; Mehler reaction ; cyclic PS I ; chlorophyll fluorescence ; 9-aminoacridine fluorescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Simultaneous measurements of 9-aminoacridine (9-AA) fluorescence quenching, O2-uptake and chlorophyll fluorescence of intact spinach chloroplasts were carried out to assess the relationship between the transthylakoidal ΔpH and linear electron flux passing through Photosystem II. Three different types of O2-dependent electron flow were investigated: (1) Catalysed by methyl viologen; (2) in the absence of a catalyst and presence of an active ascorbate peroxidase (Mehler-peroxidase reaction); (3) in the absence of a catalyst and with the ascorbate peroxidase being inhibited by KCN (Mehler reaction). The aim of this study was to assess the relative contribution of ΔpH-formation which is not associated with electron flow through Photosystem II and, which should reflect Photosystem I cyclic flow under the different conditions. The relationship between the extent of 9-AA fluorescence quenching and O2-uptake rate was found to be almost linear when methyl viologen was present. In the absence of methyl viologen (Mehler reaction) an increase of 9-AA fluorescence quenching to a value of 20% at low light intensities was associated with considerably less O2-uptake than in the presence of methyl viologen, indicating the involvement of cyclic flow. These findings are in agreement with a preceding study of Kobayashi and Heber (1994). However, when no KCN was added, such that the complete Mehler-peroxidase reaction sequence was operative, the relationship between 9-AA fluorescence quenching and the flux through PS II, as measured via the chlorophyll fluorescence parameter ΔF/Fm′ × PAR, was identical to that observed in the presence of methyl viologen. Under the assumption that methyl viologen prevents cyclic flow, it is concluded that there is no significant contribution of cyclic electron flow to ΔpH-generation in intact spinach chloroplasts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183045
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  • 63
    Digitale Medien
    Digitale Medien
    Thermoluminescence investigations on the site of action of o-phthalaldehyde in photosynthetic electron transport (1996)
    Springer
    Photosynthesis research 48 (1996), S. 213-220 
    Details
    ISSN: 1573-5079
    Schlagwort(e): Arnold ; chemical modification ; electron transfers ; oxygen evolution ; o-phthalaldehyde ; photosynthesis ; photosystems ; thermoluminescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Glow curves from spinach leaf discs infiltrated with o-phthalaldehyde (OPA) show significant similarity to those obtained by DCMU treatment which is known to block the electron flow from QA, the stable acceptor of Photosystem II (PS II). In both the cases, the thermoluminescence (TL) peak II (Q band) was intensified significantly, whereas peaks III and IV (B band) were suppressed. Total TL yield of the glow curve remained constant even when the leaf discs were infiltrated with high concentrations of OPA (4 mM) or with DCMU (100 μM), indicating that even at these high concentrations no significant change in the number of species undergoing charge recombination in PS II occurred. However, studies with thylakoids revealed significant differences in the action of OPA and DCMU on PS II. Although OPA, at a certain concentration and time of incubation, reduced the B band intensity by about 50–70%, and completely abolished the detectable oxygen evolution, it still retained the TL flash yield pattern, and, thus, S state turnover. OPA is known to inhibit the oxidoreductase activity of in vitro Cyt b6/f (Bhagwat et al. (1993) Arch Biochem Biophys 304: 38–44). However, in the OPA treated thylakoids the extent of inhibition of O2 evolution was not reduced even in the presence of oxidized tetramethyl-p-phenylenediamine which accepts electrons from plastoquinol and feeds then directly to Photosystem I. This suggests that OPA inhibition is at a site prior to plastoquinone pool in the electron transport chain, in agreement with it being between QA and QB. However, an unusual feature of OPA inhibition is that even though all oxygen evolution was completely suppressed, a significant fraction of PS II centers were functional and turned over with the same periodicity of four in the absence of any added electron donor, an observation which appears to be similar to that reported by Wydrzynski (Wydrzynski et al. (1985) Biochim Biophys Acta 809: 125–136) with lauroylcholine chloride, a lipid analogue compound. The detailed chemistry of OPA inhibition remains to be studied. Since we dedicate this paper to William A. Arnold, discoverer of delayed light and TL in photosynthesis, we have also included in the Introduction, a brief history of how TL work was initiated at BARC (Bombay, India).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00041011
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  • 64
    Digitale Medien
    Digitale Medien
    Influence of photoheterotrophy on the expression of chlorophyll a/b-binding proteins in the green alga Pyrobotrys stellata (1996)
    Springer
    Photosynthesis research 49 (1996), S. 49-56 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll a/b-binding (CAB) protein ; cyclic electron flow ; gene-expression ; light-harvesing complex (LHC) ; photosynthesis ; Pyrobotrys (Chlamydobotrys) stellata
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two genes (lhca5 and lhcb1) from the unicellular, green alga Pyrobotrys (formerly Chlamydobotrys) stellata were isolated, coding for Chlorophyll a/b-binding proteins that putatively represent constituents of the light-harvesting complexes connected with Photosystem I and Photosystem II, respectively. Expression of both genes on the mRNA-level is markedly inhibited by CO2-depletion. The lhca5 transcript-level was reduced to about 25%, and the lhcb1-expression was completely blocked 9 h after removal of CO2 from the growth medium. Simultaneous addition of acetate, which can substitute for CO2 as a carbon source during photoheterotrophic growth of P. stellata, did not compensate for the diminishing effect of CO2-depletion on lhcb1. However, the amount of lhca5 transcript was comparable to that during photoautotrophic growth. These results are interpreted in terms of the specific metabolic demands of photoheterotrophic growth in P. stellata. Cyclic electron-transfer along Photosystem I must be sustained for ATP-production. Linear electron transport fed by Photosystem II and concomitant production of NADPH for CO2-reduction is no longer required. The sequences reported in this article have been deposited at the EMBL data library under the accession numbers X69434 (CSCAB1) and X71965 (CSCAB2MR).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029427
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  • 65
    Digitale Medien
    Digitale Medien
    Characterization of the csmD and csmE genes from Chlorobium tepidum. The CsmA, CsmC, CsmD, and CsmE proteins are components of the chlorosome envelope (1996)
    Springer
    Photosynthesis research 50 (1996), S. 41-59 
    Details
    ISSN: 1573-5079
    Schlagwort(e): green sulfur bacterium ; Chlorobium tepidum ; chlorosomes ; DNA sequence ; protein overproduction ; primer extension mapping ; light-harvesting antenna ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The csmD and csmE genes, encoding two proteins of the chlorosome envelope, have been cloned and sequenced from the green sulfur bacterium Chlorobium tepidum. The csmD gene predicts a hydrophobic protein of 113 amino acids with a molecular mass of 11.1 kDa. The csmE gene was identified immediately upstream from csmD; the csmE gene predicts a protein of 82 amino acids (9.0 kDa) which is 49% identical to CsmA (Chung et al. (1994) Photosynthesis Res 41: 261–275). The CsmE protein is post-translationally processed, most likely in a manner similar to CsmA. The csmE and csmD genes are cotranscribed as a dicistronic mRNA but can also be cotranscribed with an open reading frame upstream from csmE that predicts a protein with sequence similarity to the CheY and SpoOF subclass of regulatory proteins. The CsmA, CsmC, CsmD, and CsmE proteins were overproduced in Escherichia coli, purified, and used to raise polyclonal antibodies in rabbits. Protease susceptibility mapping and agglutination experiments using these antibodies indicate that all four proteins are exposed at the surface of isolated chlorosomes and hence are probably components of the chlorosome envelope. Additionally, antigalactose antibodies were used to confirm that the galactosyl moiety of monogalactosyl diglycerol is exposed at the chlorosome surface; this is consistent with the notion that these lipids are components of the chlorosome envelope.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00018220
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  • 66
    Digitale Medien
    Digitale Medien
    Carbohydrate and carbon metabolite accumulation responses in leaves of ozone tolerant and ozone susceptible spinach plants after acute ozone exposure (1996)
    Springer
    Photosynthesis research 50 (1996), S. 103-115 
    Details
    ISSN: 1573-5079
    Schlagwort(e): glucose ; hexose phosphates ; ozone ; photosynthesis ; respiratory substrates ; starch ; sucrose
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The objective of this study was to determine whether exposure of plants to ozone (O3) increased the foliar levels of glucose, glucose sources, e.g., sucrose and starch, and glucose-6-phosphate (G6P), because in leaf cells, glucose is the precursor of the antioxidant, L-ascorbate, and glucose-6-phosphate is a source of NADPH needed to support antioxidant capacity. A further objective was to establish whether the response of increased levels of glucose, sucrose, starch and G6P in leaves could be correlated with a greater degree of plant tolerance to O3. Four commercially available Spinacia oleracea varieties were screened for tolerance or susceptibility to detrimental effects of O3 employing one 6.5 hour acute exposure to 25O nL O3 L-1 air during the light. One day after the termination of ozonation (29 d post emergence), leaves of the plants were monitored both for damage and for gas exchange characteristics. Cultivar Winter Bloomsdale (cv Winter) leaves were least damaged on a quantitative grading scale. The leaves of cv Nordic, the most susceptible, were approximately 2.5 times more damaged. Photosynthesis (Pn) rates in the ozonated mature leaves of cv Winter were 48.9% less, and in cv Nordic, 66.2% less than in comparable leaves of their non-ozonated controls. Stomatal conductance of leaves of ozonated plants was found not to be a factor in the lower Pn rates in the ozonated plants. At some time points in the light, leaves of ozonated cv Winter plants had significantly higher levels of glucose, sucrose, starch, G6P, G1P, pyruvate and malate than did leaves of ozonated cv Nordic plants. It was concluded that leaves of cv Winter displayed a higher tolerance to ozone mediated stress than those of cv Nordic, in part because they had higher levels of glucose and G6P that could be mobilized during diminished photosynthesis to generate antioxidants (e.g., ascorbate) and reductants (e.g., NADPH). Elevated levels of both pyruvate and malate in the leaves of ozonated cv Winter suggested an increased availability of respiratory substrates to support higher respiratory capacity needed for repair, growth, and maintenance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014882
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  • 67
    Digitale Medien
    Digitale Medien
    Characteristics of photosynthetic carbon metabolism of spikelets in rice (1997)
    Springer
    Photosynthesis research 52 (1997), S. 75-82 
    Details
    ISSN: 1573-5079
    Schlagwort(e): lemma ; light-enhanced dark CO2 fixation ; palea ; panicle ; photosynthesis ; pyruvate ; Pi dikinase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In lemmas and paleae of rice, the amount of pyruvate, Pi dikinase (PPDK) protein increased dramatically 6 d after anthesis and this change was consistent with that in the activity of PPDK. Since lemmas and paleae at this stage also showed high activities of the other marker enzymes of C4 pathway including phosphot enolpyruvate carboxylase (Imaizumi et al. (1990) Plant Cell Physiol 31: 835–843), photosynthetic carbon metabolism with lemmas at this stage were characterized. In a 14C pulse-12C chase study by photosynthetic CO2 fixation, about 35% and 25% of 14C fixed in lemmas were incorporated initially into 3-phosphoglycerate (3-PGA) and C4 acids, respectively. This suggests that lemmas participate mainly in C3-type photosynthetic metabolism, but that lemmas may also participate in the metabolism of C4 acids to some extent. To clarify this possibility, large amounts of 14C-labeled C4 acids were synthesized in vivo by a light-enhanced dark CO2 fixation (LED) method and the fate of 14C in C4 acids in the light was investigated. The percentage distribution of 14C in C-4 position of malate was about 90% and 83% after 10 s of photosynthetic 14CO2 fixation and 110 s of LED, respectively. Some of the 14C incorporated into C4 acids was transferred into 3-PGA and sugar phosphates. The possibility of direct fixation of CO2 by phosphot enolpyruvate carboxylase and metabolic pathway of CO2 released by decarboxylation of malate produced were discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005887931498
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  • 68
    Digitale Medien
    Digitale Medien
    Photosynthetic plasticity in Potamogeton pectinatus L. from Argentina: strategies to survive adverse light conditions (1996)
    Springer
    Hydrobiologia 340 (1996), S. 1-5 
    Details
    ISSN: 1573-5117
    Schlagwort(e): light climate manipulation ; Potamogeton pectinatus ; photosynthesis ; turbidity ; weed management
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Argentine Potamogeton pectinatus L. was grown in The Netherlands under laboratory conditions at four light intensities (50, 100, 150 and 200 µE m−2 s−1), and photosynthetic performance was evaluated after about 1, 2 and 3 months of growth. At these moments, chlorophyll-a and -b and tissue N and P content were also determined. During the growing period, plant lengths and number of secondary shoots were measured. In the field in Argentina, photosynthetic performance of P. pectinatus was also measured at different light intensities created by artificial shading at various times during the growing season. Field and laboratory photosynthetic results were in good agreement. P. pectinatus showed a significant plasticityin its photosynthesis, rather than in morphology. A fairly constant maximum photosynthetic rate with reduced light enabled the plants to maintain netproduction rates rather unaffected at low light intensities. Still, it can be predicted that increasing turbidity from 1–2 m−1 at present to 3 m−1 could lead to a strongly light-limited growth which should reduce the present weed problem considerably. Such a turbidity increase might be achieved by the introduction of a fairly dense bottom-feeding fish population like Common carp (Cyprinus carpio L.).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00012725
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  • 69
    Digitale Medien
    Digitale Medien
    Growth at high CO2 affects the chloroplast number but not the photosynthetic efficiency of photoautotrophicMarchantia polymorpha culture cells (1997)
    Springer
    Plant cell, tissue and organ culture 48 (1997), S. 103-110 
    Details
    ISSN: 1573-5044
    Schlagwort(e): bryophytes ; cell culture ; chlorophyll content ; LHC II ; photosynthesis ; Rubisco
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photoautotrophic suspension cells of Marchantia polymorpha were grown at gas phase CO2 concentrations of 0.4% and 2.0%. At the higher CO2 concentration the chloroplast shape appeared to be modified and the cells had about 70% more chloroplasts per cell. Differences in chlorophyll content per cell were much less pronounced, indicating a reduction in chlorophyll content per chloroplast. Also the cell size was affected by the CO2 concentration, and our data suggest that it was about 37% lower in high CO2 grown cells than in low CO2 grown cells. The capacity and the efficiency of photosynthetic oxygen evolution on a chlorophyll basis and the photosystem II chlorophyll fluorescence parameters were almost identical in both cell types. Immunodection showed that also the ratio of light harvesting complex II antenna proteins and ribulose 1,5 bisphosphate carboxylase/oxygenase were unaltered. These data indicate that the chloroplast density within photoautotrophic culture cells may be regulated independently of their photosynthetic efficiency.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005893311140
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  • 70
    Digitale Medien
    Digitale Medien
    Effects of two sesquiterpene lactones isolated fromArtemisia annua on physiology ofLemna minor (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 969-978 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Artemisinin ; arteannuic acid ; photosynthesis ; respiration ; chlorophyll ; Lemna minor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The effects of artemisinin and arteannuic acid extracted fromArtemisia annua on the physiology ofLemna minor were evaluated. Changes in frond production, growth, dry weight, and chlorophyll content ofL. minor were determined. Photosynthesis and respiration were evaluated with a differential respirometer. Artemisinin (5 µM) inhibitedL. minor frond production and dry weight 82 and 83%, relative to methanol controls. Chlorophyll content was reduced 44% by artemisinin (2.5 µM). Arteannuic acid (10 µM) was less active, inhibiting frond production 61% and reducing chlorophyll content 66% at 5 µM. Artemisinin (1 µM) reducedL. minor photosynthesis 30% and 2.5 µM reduced respiration 39%. Arteannuic acid had no significant effect on photosynthesis or respiration at the levels tested.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02059591
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  • 71
    Digitale Medien
    Digitale Medien
    Photosynthetic electron transport and anaerobic metabolism in purple non-sulfur phototrophic bacteria (1994)
    Springer
    Antonie van Leeuwenhoek 66 (1994), S. 151-164 
    Details
    ISSN: 1572-9699
    Schlagwort(e): purple non-sulfur bacteria ; Rhodobacter ; photosynthesis ; CO2 fixation ; anaerobic respiration ; gene expression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Purple non-sulfur phototrophic bacteria, exemplifed byRhodobacter capsulatus andRhodobacter sphaeroides, exhibit a remarkable versatility in their anaerobic metabolism. In these bacteria the photosynthetic apparatus, enzymes involved in CO2 fixation and pathways of anaerobic respiration are all induced upon a reduction in oxygen tension. Recently, there have been significant advances in the understanding of molecular properties of the photosynthetic apparatus and the control of the expression of genes involved in photosynthesis and CO2 fixation. In addition, anaerobic respiratory pathways have been characterised and their interaction with photosynthetic electron transport has been described. This review will survey these advances and will discuss the ways in which photosynthetic electron transport and oxidation-reduction processes are integrated during photoautotrophic and photoheterotrophic growth.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00871637
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  • 72
    Digitale Medien
    Digitale Medien
    Protein structure, electron transfer and evolution of prokaryotic photosynthetic reaction centers (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 311-329 
    Details
    ISSN: 1572-9699
    Schlagwort(e): photosynthesis ; chlorophyll ; bacteriochlorophyll ; reaction center ; electron transfer ; evolution
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic reaction centers from a variety of organisms have been isolated and characterized. The groups of prokaryotic photosynthetic organisms include the purple bacteria, the filamentous green bacteria, the green sulfur bacteria and the heliobacteria as anoxygenic representatives as well as the cyanobacteria and prochlorophytes as oxygenic representatives. This review focuses on structural and functional comparisons of the various groups of photosynthetic reaction centers and considers possible evolutionary scenarios to explain the diversity of existing photosynthetic organisms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00872216
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  • 73
    Digitale Medien
    Digitale Medien
    Mepiquat chloride (PIX)-induced changes in photosynthesis and growth of cotton (1996)
    Springer
    Plant growth regulation 20 (1996), S. 179-183 
    Details
    ISSN: 1573-5087
    Schlagwort(e): cotton ; growth ; mepiquat chloride ; photosynthesis ; PIX ; RuBP carboxylase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Mepiquat chloride (N, N-dimethylpiperidinium chloride), well known as PIX, is a potential systemic plant growth regulator. The effects of PIX on plant height, stem elongation, leaf area, net photosynthetic rates, chlorophyll content, sucrose and starch levels, and RuBP carboxylase activity in cotton (Gossypium hirsutum L. cv. DES 119) plants were measured. PIX was sprayed (0, 7.65, 15.3, 30.6 or 61.2 g active ingredient ha−1) on the plants at first square (25 days after emergence) and measurements were made at frequent intervals. Plant height was clearly reduced by PIX. The total length of vegetative branches and fruiting branches was 40% and 50% less than the control. Total leaf area in PIX treated plants was 16% less than the control. Net photosynthetic rates were 25% less in PIX-treated leaves. PIX treated leaves had more chlorophyll content. The activity of RuBP carboxylase was decreased in PIX treated plants. Starch accumulation was noticed in PIX treated leaves while sucrose content was not changed. The data reported here suggest that reduced growth responses induced by PIX results in partial loss of photosynthetic capacity in cotton at least up to 20 days after application of the growth regulator.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00043305
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  • 74
    Digitale Medien
    Digitale Medien
    Developmental changes in carboxylase activities in in vitro cultured coconut zygotic embryos: comparison with corresponding activities in seedlings (1997)
    Springer
    Plant cell, tissue and organ culture 49 (1997), S. 227-231 
    Details
    ISSN: 1573-5044
    Schlagwort(e): carbon metabolism ; CO2 fixation ; embryo culture ; PEPC ; photosynthesis ; RubisCO
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Phosphoenolpyruvate Carboxylase (PEPC; EC: 4.1.1.31) and Ribulose 1,5-bisphosphate Carboxylase/Oxygenase (RubisCO; EC: 4.1.1.39) enzyme specific activities were measured during the in vitro development of coconut (Cocos nucifera L.) zygotic mature embryos into plantlets and compared with those of palms produced by conventional seed germination. At the time of initiation of germination, high PEPC and low RubisCO activities were measured in both cultured and conventionally germinated embryos, thus indicating an anaplerotic CO2 fixation. During both in vitro and in planta development, RubisCO progressively took over and became the main route for inorganic carbon fixation. The in vitro-grown coconut plantlets showed a faster decrease in their PEPC:RubisCO ratio than the seedlings, suggesting that an earlier transition from a heterotrophic to an autotrophic mode of carbon fixation takes place in the in vitro-derived material. Just before acclimatization, the RubisCO activity in in vitro-derived plantlets (2.83 µmol CO2h−1mg−1 TSP) was lower than that in seedlings (6.98 µmol CO2h−1mg−1 TSP) of the same age. Nevertheless, after acclimatization, RubisCO activities were comparable in both in vitro and in planta germinated material
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005856212846
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  • 75
    Digitale Medien
    Digitale Medien
    Development of photoautotrophy and photoinhibition of Gardenia jasminoides plantlets during micropropagation (1996)
    Springer
    Plant cell, tissue and organ culture 45 (1996), S. 1-16 
    Details
    ISSN: 1573-5044
    Schlagwort(e): chlorophyll fluorescence ; leaf anatomy ; photosynthesis ; root induction ; shoot multiplication ; stable carbon isotope composition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This paper reports on the fast fluorescence responses of Gardenia jasminoides Ellis plantlets, at two successive stages (shoot multiplication and root induction) of culture in vitro. We test whether plantlets in vitro suffer photoinhibition during culture and whether the degree of photoautotrophy of these mixotrophic plantlets has any effect on the extent of photoinhibitory impairment. In this regard the effects of different sucrose levels in the medium and PPFD during growth on the development of photoautotrophy and the extent of photoinhibition were evaluated. Plantlets were grown under low, intermediate, and high (50, 100, and 300 μmol m-2 s-1) PPFD, and at 3 different sucrose concentrations (0.5, 1.5, and 3.0%, w/v) in the medium, during shoot multiplication. During root induction the same growth conditions were assayed except for the high PPFD. The development of photoautotrophy was assessed via the difference between the stable carbon isotope composition of sucrose used as heterotrophic carbon source and that of leaflets grown in vitro. Plantlets from root induction showed more developed photoautotrophy than those from shoot multiplication. For both stages the low-sucrose medium stimulated the photoautotrophy of plantlets in vitro. In addition, intermediate PPFD induced photoautotrophy during shoot multiplication. For plantlets of both culture stages at the lowest PPFD no photoinhibition occurred irrespective of the sucrose concentration in media. However, during the shoot multiplication stage chlorophyll fluorescence measurements showed a decrease in F v /F m and in t 1/2 as growing PPFD increased, indicating photoinhibitory damage. The decline of F v /F m was caused mostly by an increase in F o , indicating the inactivation of PSII reaction centers. However plantlets growing under low sucrose showed reduced susceptibility to photoinhibition. During root induction, only plantlets cultured with high sucrose showed a decrease in F v /F m as PPFD increased, although t 1/2 remained unchanged. In this case, the decline of F v /F m was mostly due to a decrease in F m , which indicates increased photoprotection rather than occurrence of photodamage. Therefore, growth in low-sucrose media had a protective effect on the resistance of PSII to light stress. In addition, plantlets were more resistant to photoinhibition during root induction than during shoot multiplication. Results suggest that increased photoautotrophy of plantlets reduces susceptibility to photoinhibition during gardenia culture in vitro.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00043422
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  • 76
    Digitale Medien
    Digitale Medien
    Genetic variation for resistance to low-temperature photoinhibition of photosynthesis in maize (Zea mays L.) (1994)
    Springer
    Euphytica 80 (1994), S. 85-93 
    Details
    ISSN: 1573-5060
    Schlagwort(e): maize ; Zea mays ; photoinhibition ; photosynthesis ; low-temperature adaptation ; breeding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Sixty-seven inbred lines of maize were evaluated for resistance to low-temperature photoinhibition of photosynthesis, using a pulse-modulated chlorophyll fluorescence technique. The evaluation procedure was based on leaf discs, which were exposed to a high irradiance (1000 µmol/m2/s) at 7°C. The efficiency of open PSII reaction centres as a reflection of overall photosynthesis was measured before and after a photoinhibition-inducing treatment. Exposure of leaf discs to photoinhibitory condition for 2, 4, and 8 hours resulted in an efficiency reduction of 30, 53 and 83%, respectively. Testing of inbred lines showed large differences for photoinhibition susceptibility. The difference in photosynthetic efficiency between the most extreme lines after a treatment of eight hours was 39%. Resistance to photoinhibition was shown to be relevant under cool field conditions. It proved to be a trait strongly amenable to selection.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039302
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  • 77
    Digitale Medien
    Digitale Medien
    Optimal acclimation of the C3 photosynthetic system under enhanced CO2 (1994)
    Springer
    Photosynthesis research 39 (1994), S. 401-412 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; elevated CO2 ; source-sink interactions ; Rubisco
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A range of studies of C3 plants have shown that there is a change in both the carbon flux and the pattern of nitrogen allocation when plants are grown under enhanced CO2. This paper examines evidence that allocation of nitrogen both to and within the photosynthetic system is optimised with respect to the carbon flux. A model is developed which predicts the optimal relative allocation of nitrogen to key enzymes of the photosynthetic system as a function of CO2 concentration. It is shown that evidence from flux control analysis is broadly consistent with this model, although at high nitrogen and under certain conditions at low nitrogen experimental data are not consistent with the model. Acclimation to enhanced CO2 is also assessed in terms of resource allocation between photosynthate sources and sinks. A means of assessing the optimisation of this source-sink allocation is proposed, and several studies are examined within this framework. It is concluded that C3 plants probably possess the genetic feedback mechanisms required to efficiently ‘smooth out” any imbalance within the photosynthetic system caused by a rise in atmospheric CO2.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014594
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  • 78
    Digitale Medien
    Digitale Medien
    Biochemical and molecular basis for impairment of photosynthetic potential (1994)
    Springer
    Photosynthesis research 39 (1994), S. 453-462 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; Rubisco ; ozone ; oxidative stress ; rbcS mRNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Ozone induces reductions in net photosynthesis in a large number of plant species. A primary mechanism by which photosynthesis is reduced is through impact on carbon dioxide fixation. Ozone induces loss in Rubisco activity associated with loss in concentration of the protein. Evidence is presented that ozone may induce oxidative modification of Rubisco leading to subsequent proteolysis. In addition, plants exposed to ozone sustain reduction in rbcS, the mRNA for the small subunit of Rubisco. This loss in rbcS mRNA may lead to a reduced potential for synthesis of the protein. The regulation of O3-induced loss of Rubisco, and implications of the decline in this protein in relation to accelerated senescence are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014598
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  • 79
    Digitale Medien
    Digitale Medien
    Reminiscence about‘Chloropseudomonas ethylicum’ and the FMO-protein (1994)
    Springer
    Photosynthesis research 41 (1994), S. 3-5 
    Details
    ISSN: 1573-5079
    Schlagwort(e): bacteriochlorophylla-protein ; green sulfur bacteria ; Prosthecochloris aestuarii ; Chlorobium limicola ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In 1961 the green sulfur bacterium-containing mixed culture known as‘Chloropseudomonas ethylicum’ was brought to Brookhaven National Laboratory (USA) from Moscow State University (USSR). The water-soluble bacteriochlorophylla-protein (FMO-protein) was extracted, purified and characterized by absorption and circular dichroism spectroscopy, by X-ray crystallography and by primary structure determination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184138
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  • 80
    Digitale Medien
    Digitale Medien
    Rates of vectorial proton transport supported by cyclic electron flow during oxygen reduction by illuminated intact chloroplasts (1994)
    Springer
    Photosynthesis research 41 (1994), S. 419-428 
    Details
    ISSN: 1573-5079
    Schlagwort(e): 9-aminoacridine fluorescence ; cyclic electron transport ; Mehler reaction ; photosynthesis ; photosystems ; transthylakoid proton gradient
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The light-dependent quenching of 9-aminoacridine fluorescence was used to monitor the state of the transthylakoid proton gradient in illuminated intact chloroplasts in the presence or absence of external electron acceptors. The absence of appreciable light-dependent fluorescence quenching under anaerobic conditions indicated inhibition of coupled electron transport in the absence of external electron acceptors. Oxygen relieved this inhibition. However, when DCMU inhibited excessive reduction of the plastoquinone pool in the absence of oxygen, coupled cyclic electron transport supported the formation of a transthylakoid proton gradient even under anaerobiosis. This proton gradient collapsed in the presence of oxygen. Under aerobic conditions, and when KCN inhibited ribulose bisphosphate carboxylase and ascorbate peroxidase, fluorescence quenching indicated the formation of a transthylakoid proton gradient which was larger with oxygen in the Mehler reaction as electron acceptor than with methylviologen at similar rates of linear electron transport. Apparently, cyclic electron transport occured simultaneously with linear electron transport, when oxygen was available as electron acceptor, but not when methylviologen accepted electrons from Photosystem I. The ratio of cyclic to linear electron transport could be increased by low concentrations of DCMU. This shows that even under aerobic conditions cyclic electron transport is limited in isolated intact chloroplasts by excessive reduction of electron carriers. In fact, P700 in the reaction center of Photosystem I remained reduced in illuminated isolated chloroplasts under conditions which resulted in extensive oxidation of P700 in leaves. This shows that regulation of Photosystem II activity is less effective in isolated chloroplasts than in leaves. Assuming that a Q-cycle supports a H+/e ratio of 3 during slow linear electron transport, vectorial proton transport coupled to Photosystem I-dependent cyclic electron flow could be calculated. The highest calculated rate of Photosystem I-dependent proton transport, which was not yet light-saturated, was 330 μmol protons (mg chlorophyll h)−1 in intact chloroplasts. If H+/e is not three but two proton transfer is not 330 but 220 μmol (mg Chl H)−1. Differences in the regulation of cyclic electron transport in isolated chloroplasts and in leaves are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183044
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  • 81
    Digitale Medien
    Digitale Medien
    Pigment orientation changes accompanying the light state transition in Synechococcus sp. PCC 6301 (1994)
    Springer
    Photosynthesis research 40 (1994), S. 35-44 
    Details
    ISSN: 1573-5079
    Schlagwort(e): allophycocyanin ; chlorophyll a ; linear dichroism ; phycobilisome ; photosynthesis ; state transition
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Low temperature (77 K) linear dichroism spectroscopy was used to characterize pigment orientation changes accompanying the light state transition in the cyanobacterium, Synechococcus sp. PCC 6301 and those accompanying chromatic acclimation in Porphyridium cruentum in samples stabilized by glutaraldehyde fixation. In light state 2 compared to light state 1 intact cells of Synechococcus showed an increased alignment of allophycocyanin parallel to the cells' long axis whereas the phycobilisomethylakoid membrane fragments exhibited an increased allophycocyanin alignment parallel to the membrane plane. The phycobilisome-thylakoid membrane fragments showed less alignment of a short wave-length chlorophyll a (Chl a) Qy transition dipole parallel to the membrane plane in state 2 relative to state 1. To aid identification of the observed Chl a orientation changes in Synechococcus, linear dichroism spectra were obtained from phycobilisome-thylakoid membrane fragments isolated from red light-grown (increased number of PS II centres) and green light-grown (increased number of PS I centres) cells of the red alga Porphyridium cruentum. An increased contribution of short wavelength Chl a Qy transition dipoles parallel to the long axis of the membrane plane was directly correlated with increased levels of PS II centres in red light-grown P. cruentum. Our results indicate that the transition to state 2 in cyanobacteria is accompanied by an increase in the orientation of allophycocyanin and a decrease in the orientation of Chl a associated with PS II with respect to the thylakoid membrane plane.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019043
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  • 82
    Digitale Medien
    Digitale Medien
    Photoinhibition of photosynthesis in chilled potato leaves is not correlated with a loss of Photosystem-II activity (1994)
    Springer
    Photosynthesis research 40 (1994), S. 75-92 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chilling temperature ; oxygen toxicity ; photoinhibition ; photosynthesis ; photosystems ; superoxide dismutase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract When 23 °C-grown potato leaves (Solanum tuberosum L.) were irradiated at 23 °C with a strong white light, photosynthetic electron transport and Photosystem-II (PS II) activity were inhibited in parallel. When the light treatment was given at a low temperature of 3 °C, the photoinhibition of photosynthesis was considerably enhanced, as expected. Surprisingly, no such stimulation of photoinhibition was observed with respect to the PS II function. A detailed functional analysis of the photosynthetic apparatus, using in-vivo fluorescence, absorbance, oxygen and photoacoustic measurements, and artificial electron donors/acceptors, showed a pronounced alteration of PS I activity during light stress at low temperature. More precisely, it was observed that both the pool of photooxidizeable reaction center pigment (P700) of PS I and the efficiency of PS I to oxidize P700 were dramatically reduced. Loss of P700 activity was shown to be essentially dependent on atmospheric O2 and to require a continued flow of electrons from PS II, suggesting the involvement of the superoxide anion radical which is produced by the interaction of O2 and the photosynthetic electron-transfer chain through the Mehler reaction. Mass spectrometric measurements of O2 exchange by potato leaves under strong illumination did not reveal, however, any stimulation of the Mehler reaction at low temperature, thus leading to the conclusion that O2 toxicity mainly resulted from a chilling-induced inhibition of the scavenging system for O2-radicals. Support for this interpretation was provided by the light response of potato leaves infiltrated with an inhibitor (diethyldithiocarbamate) of the chloroplastic Cu-Zn superoxide dismutase. It was indeed possible to simulate the differential inhibition of the PS II photochemical activity and the linear electron transport observed during light stress at low temperature by illuminating at 23 °C diethyldithiocarbamate-poisoned leaves. The experimental data presented here suggests that (i) the previously reported resistance of PS I to photoinhibition damage in-vivo is not an intrinsic property of PS I but results from efficient protective systems against O2 toxicity, (ii) PS I is photoinhibited in chilled potato leaf due to the inactivation of this PS I defence system and (iii) PS I is more sensitive to superoxide anion radicals than PS II.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019047
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  • 83
    Digitale Medien
    Digitale Medien
    Sixty years in algal physiology and photosynthesis (1994)
    Springer
    Photosynthesis research 40 (1994), S. 207-221 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; unicellular algae ; ion effects ; manganese ; blue light ; synchronized growth ; algal mass cultures
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This personal perspective records research experiences in chemistry and biology at four German universities, two before and two after World War II. The research themes came from cytophysiology of green unicellular algae, in particular their photosynthesis. The function of inorganic ions in photosynthesis and dark respiration was investigated at different degrees of specific mineral stress (deficiencies), and the kinetics of recovery followed after the addition of the missing element. Two types of recovery of photosynthesis were observed: indirect restitution via growth processes and immediate normalisation. From the latter case (K+, phosphate, Mn++) the effect of manganese was emphasized as its role in photosynthetic O2 evolution became established during our research. Other themes of our group, with some bearing on photosynthesis were: synchronization of cell growth by light-dark change and effects of blue (vs. red) light on the composition of green cells. Some experiences in connection with algal mass cultures are included. Discussion of several editorial projects shows how photosynthesis, as an orginally separated field of plant biochemistry and biophysics, became included into general cell physiology and even ecophysiology of green plants. The paper contains an appreciation of the authors' main mentor Kurt Noack (1888–1963) and of Ernst Georg Pringsheim (1881–1970), founder of experimental phycology.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00034771
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  • 84
    Digitale Medien
    Digitale Medien
    Gene nomenclature recommendations for green photosynthetic bacteria and heliobacteria (1994)
    Springer
    Photosynthesis research 41 (1994), S. 27-28 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; reaction center ; green bacteria ; heliobacteria ; gene ; chlorosome ; cytochrome
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Recommendations are given for naming of genes coding for reaction center, antenna and electron transport proteins in green photosynthetic bacteria and heliobacteria
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184142
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  • 85
    Digitale Medien
    Digitale Medien
    Redox effects on the bacteriochlorophyll α-containing Fenna-Matthews-Olson protein fromChlorobium tepidum (1994)
    Springer
    Photosynthesis research 41 (1994), S. 89-96 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; Chlorobium tepidum ; antenna ; bacteriochlorophylla protein ; energy transfer ; chlorosome ; green bacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The BChla-containing Fenna-Matthews-Olson (FMO) protein from the green sulfur bacteriumChlorobium tepidum was purified and characterized. Fluorescence spectra indicate that efficient excited state quenching occurs at neutral or oxidizing redox potentials. The major fluorescence lifetime at room temperature is approximately 60 ps in samples that are in neutral or oxidizing conditions, and approximately 2 ns in samples where the strong reductant sodium dithionite has been added. A similar change is observed in pump-probe picosecond absorbance difference experiments, where the long life time component increases after dithionite addition. A 16 Gauss wide EPR signal with g factor =2.005 is observed in samples without dithionite. This signal largely disappears upon addition of dithionite. Dithionite induces large reversibile changes in the 77 K absorbance spectra of the purified FMO protein and in whole cells. These results indicate that the FMO protein contains redox active groups, which may be involved in the regulation of energy transfer. Room temperature circular dichroism and low temperature absorption spectra show that dithionite also induces conformational or structural changes of the FMO protein complex.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184148
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  • 86
    Digitale Medien
    Digitale Medien
    Responses to drought and flooding in tropical forage grasses (1994)
    Springer
    Plant and soil 164 (1994), S. 97-105 
    Details
    ISSN: 1573-5036
    Schlagwort(e): alcohol dehydrogenase ; drought ; flooding ; photosynthesis ; tropical grasses ; water potential
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Long dry seasons or permanent flooding, typical of tropical savannas, severely limit the growth of pasture plants. This study compares the responses of water relations, carbon assimilation and alcohol dehydrogenase (ADH) activity to drought and flooding in four perennial C4 grasses: the tufted or caespitose Hyparrhenia rufa and Andropogon gayanus (CIAT 621) and the stoloniferous Brachiaria mutica and Echinochloa polystachya. Plants of the four species were subjected to medium term flooding (20–25 days) and moderate drought in a greenhouse. Leaf water potential (Ψ), stomatal conductance (Gs) and photosynthesis rate (Pn) were measured throughout the experiment and ADH activity was measured in flooded and control plants. Moderate drought produced similar effects in all grasses reducing Gs which caused reduced Pn. Net photosynthesis compensation point was reached at the lowest Ψ in A. gayanus which was considered as the most drought tolerant. The responses to flooding varied across species. Andropogon gayanus and H. rufa showed early stomatal closure without concurrent decrease in Ψ and leaf turgor. This low Gs was responsible of reduced Pn and growth rate. There was a slight increase of Gs in the middle of the flooding period and both grasses recovered pre-stress Gs and Pn after drainage. ADH activity increased markedly only in A. gayanus under flooding suggesting that this grass was the most flood-sensitive. Stomatal aperture, Pn and ADH activity in B. mutica and E. polystachya were not affected by flooding. The higher flood-tolerance in these grasses might be attributed to enhanced oxygen diffusion to the roots through the hollow stolons, development of advantitious rootlets and large aerenchyma in the roots which compensate for the reduction of soil oxygen and permit the maintenance of root activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00010115
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  • 87
    Digitale Medien
    Digitale Medien
    Photosynthesis in leaves and siliques of winter oilseed rape (Brassica napus L.) (1996)
    Springer
    Plant and soil 186 (1996), S. 227-236 
    Details
    ISSN: 1573-5036
    Schlagwort(e): Brassica napus ; canola ; oilseed rape ; nitrogen nutrition ; irrigation ; photosynthesis ; photosynthetic nitrogen use efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The rate of photosynthesis and its relation to tissue nitrogen content was studied in leaves and siliques of winter oilseed rape (Brassica napus L.) growing under field conditions including three rates of nitrogen application (0, 100 or 200 kg N ha-1) and two levels of irrigation (rainfed or irrigated at a deficit of 20 mm). The predominant effect of increasing N application under conditions without water deficiency was enhanced expansion of photosynthetically active leaf and silique surfaces, while the rate of photosynthesis per unit leaf or silique surface area was similar in the different N treatments. Thus, oilseed rape did not increase N investment in leaf area expansion before a decline in photosynthetic rate per unit leaf area due to N deficiency could be avoided. Much less photosynthetically active radiation penetrated into high-N canopies than into low-N canopies. The specific leaf area increased markedly in low light conditions, causing leaves in shade to be less dense than leaves exposed to ample light. In both leaves and siliques the photosynthetic rate per unit surface area responded linearly to increasing N content up to about 2 g m-2, thus showing a constant rate of net CO2 assimilation per unit increment in N (constant photosynthetic N use efficiency). At higher tissue N contents, photosynthetic rate responded less to changes in N status. Expressed per unit N, light saturated photosynthetic rate was three times higher in leaves than in silique valves, indicating a more efficient photosynthetic N utilization in leaves than in siliques. Nevertheless, from about two weeks after completion of flowering and onwards total net CO2 fixation in silique valves exceeded that in leaves because siliques received much higher radiation intensities than leaves and because the leaf area declined rapidly during the reproductive phase of growth. Water deficiency in late vegetative and early reproductive growth stages reduced the photosynthetic rate in leaves and, in particular, siliques of medium- and high-N plants, but not of low-N plants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02415518
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  • 88
    Digitale Medien
    Digitale Medien
    The effect of different closure types, light, and sucrose concentrations on carbon isotope composition and growth ofGardenia jasminoides plantlets during micropropagation and subsequent acclimationex vitro (1997)
    Springer
    Plant cell, tissue and organ culture 47 (1997), S. 217-230 
    Details
    ISSN: 1573-5044
    Schlagwort(e): photoautotrophy ; photosynthesis ; shoot multiplication ; root induction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The growth ofGardenia jasminoides Ellis plantlets and the development of photoautotrophy during two successive culture stages (shoot multiplication and root induction)in vitro was analyzed. We examined the effects of changes in growth conditions (type of tube closure, light, and sugar levels) on the development of photoautotrophy and growth during micropropagation and sought to establish whether they affected later acclimation to conditionsex vitro. During the two stagesin vitro, plantlets were grown in tubes under two different PPFD (50 and 110 µmol m−2 s−1), in media with three different sucrose concentrations (0, 1.5, and 3.0%, w/v) and with two different CO2 levels inside the tubes (controlled by either tightly closed caps or loosely sealed caps, and with an external CO2 concentration of 750 µmol mol−1). The development of photoautotrophy was assessed by determining the difference between the stable carbon isotope composition (δ13C) of sugar cane sucrose used as a heterotrophic carbon source and that of leaflets grownin vitro. Plantlets from the root-induction stage showed a more highly developed photoautotrophy than those from the shoot- multiplication stage. At both stages, utilization of closed caps was the treatment which most stimulated development of photoautotrophy in plantlets. Also, lowering PPFD or sucrose concentration induced a greater degree of photoautotrophic development, the strongest effect being observed in plantlets cultured inside loosely sealed tubes. During acclimationex vitro, plantlets taken from loosely sealed tubesin vitro performed better than those cultured inside tightly sealed tubes. The former, as well as recording a larger increase in fresh weight during this stage, also showed more negative δ13C in the newly developed leaves, which would seem to indicate a better water status during acclimation. Present results validate the usefulness of δ13C analysis of leaflets as a simple technique in assessing the development of photoautotrophy during culturein vitro. In addition, δ13C analysis can be extended to evaluate growth conditions during acclimation toex vitro conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02318976
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  • 89
    Digitale Medien
    Digitale Medien
    Gene action and heritability for photosynthetic activity in two wheat crosses (1994)
    Springer
    Euphytica 76 (1994), S. 235-238 
    Details
    ISSN: 1573-5060
    Schlagwort(e): Triticum aestivum ; wheat ; photosynthesis ; gene action ; heritability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Gene action and heritability for photosynthetic activity were estimated from generation means in two wheat crosses during two stages (5 th leaf and flag leaf between 2 and 5 days after anthesis). Six generations were available for each cross: parents (P1 and P2), F1, F2 and backcrosses (BC1 and BC2). Correlations between some morphophysiological characters and photosynthetic activity of the flag leaf was also determined. The joint scaling test described by Mather & Jinks was used to determine the gene action. It showed that them; [d]; [h]; [i], [l] (mean, additivity, dominance, additive x additive interallelic interaction effects, dominance x dominance interallelic interaction effects) model fits the two crosses at both measurement times. All the model genetic components were significant for the flag leaf, however for the 5 th leaf only [h]; [i] and [l] were significant. The presence of additive and additive x additive effects suggested the possibility of selecting for this character using the flag leaf so as to obtain pure inbred lines. Dominance effects [h] were negative and dominance x dominance effects [l] were positive. Broad sense heritability values were medium to low. There were no correlations between the studied morphophysiological characters and the photosynthetic activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00022168
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  • 90
    Digitale Medien
    Digitale Medien
    Singlet oxygen production in thylakoid membranes during photoinhibition as detected by EPR spectroscopy (1994)
    Springer
    Photosynthesis research 39 (1994), S. 191-199 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photoinhibition ; photosynthesis ; protein degradation ; singlet oxygen ; TEMP (2,2,6,6-tetramethylpiperidine) ; thylakoid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Exposure of isolated spinach thylakoids to high intensity illumination (photoinhibition) results in the well-characterized impairment of Photosystem II electron transport, followed by degradation of the D1 reaction centre protein. In the present study we demonstrate that this process is accompanied by singlet oxygen production. Singlet oxygen was detected by EPR spectroscopy, following the formation of stable nitroxide radicals from the trapping of singlet oxygen with a sterically hindered amine TEMP (2,2,6,6-tetramethylpiperidine). There was no detectable singlet oxygen production during anaerob photoinhibition or in the presence of sodium-azide. Comparing the kinetics of the loss of PS II function and D1 protein with that of singlet oxygen trapping suggests that singlet oxygen itself or its radical product initiates the degradation of D1.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029386
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  • 91
    Digitale Medien
    Digitale Medien
    Changes in the antenna size of Photosystem I and Photosystem II in Synechococcus sp. strain PCC 7942 grown in the presence of SANDOZ 9785 — a Photosystem II inhibitor (1994)
    Springer
    Photosynthesis research 41 (1994), S. 303-313 
    Details
    ISSN: 1573-5079
    Schlagwort(e): cyanobacteria ; excitation energy ; herbicide ; photochemical apparatus ; photosynthesis ; pyridazinone
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract SANDOZ 9785, also known as BASF 13.338, is a pyridazinone derivative that inhibits Photosystem II (PS II) activity leading to an imbalance in the rate of electron transport through the photosystems. Synechococcus sp. strain PCC 7942 cells grown in the presence of sublethal concentration of SANDOZ 9785 (SAN 9785) for 48 hours exhibited a 20% decrease in Chl a per cell. However, no changes were observed in the content of phycocyanin per cell, the size of the phycobilisomes or in the PS II:PS I ratio. From an estimate of PS II electron transport rate under varying light intensities and spectral qualities and analysis of room temperature Chl a fluorescence induction, it was deduced that growth of Synechococcus PCC 7942 in the presence of SAN 9785 leads to a redistribution of excitation energy in favour of PS II. Though the redistribution appears to be primarily caused by changes affecting the Chl a antenna of PS II, the extent of energetic coupling between phycobilisomes and PS II is also enhanced in SAN 9785 grown Synechococcus PCC 7942 cells. There was a reduction in the effective size of PS I antenna based on measurement of P700 photooxidation kinetics. These results indicate that when PS II is partially inhibited, the structure of photosynthetic apparatus alters to redistribute the excitation energy in favour of PS II so that the efficiency of utilization of light energy by the two photosystems is optimized. Our results suggest that under the conditions used, drastic structural changes are not essential for redistribution of excitation energy between the photosystems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019408
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  • 92
    Digitale Medien
    Digitale Medien
    Acclimation of photosynthesis to increasing atmospheric CO2: The gas exchange perspective (1994)
    Springer
    Photosynthesis research 39 (1994), S. 351-368 
    Details
    ISSN: 1573-5079
    Schlagwort(e): CO2 enrichment ; gas exchange ; greenhouse effect ; photosynthesis ; responses to CO2
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The nature of photosynthetic acclimation to elevated CO2 is evaluated from the results of over 40 studies focusing on the effect of long-term CO2 enrichment on the short-term response of photosynthesis to intercellular CO2 (the A/Ci response). The effect of CO2 enrichment on the A/Ci response was dependent on growth conditions, with plants grown in small pots (〈 5 L) or low nutrients usually exhibiting a reduction of A at a given Ci, while plants grown without nutrient deficiency in large pots or in the field tended to exhibit either little reduction or an enhancement of A at a given Ci following a doubling or tripling of atmospheric CO2 during growth. Using theoretical interpretations of A/Ci curves to assess acclimation, it was found that when pot size or nutrient deficiency was not a factor, changes in the shape of A/Ci curves which are indicative of a reallocation of resources within the photosynthetic apparatus typically were not observed. Long-term CO2 enrichment usually had little effect or increased the value of A at all Ci. However, a minority of species grown at elevated CO2 exhibited gas exchange responses indicative of a reduced amount of Rubisco and an enhanced capacity to metabolize photosynthetic products. This type of response was considered beneficial because it enhanced both photosynthetic capacity at high CO2 and reduced resource investment in excessive Rubisco capacity. The ratio of intercellular to ambient CO2 (the Ci/Ca ratio) was used to evaluate stomatal acclimation. Except under water and humidity stress, Ci/Ca exhibited no consistent change in a variety of C3 species, indicating no stomatal acclimation. Under drought or humidity stress, Ci/Ca declined in high-CO2 grown plants, indicating stomata will become more conservative during stress episodes in future high CO2 environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014591
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  • 93
    Digitale Medien
    Digitale Medien
    Effects of UV-B radiation on photosynthesis and growth of terrestrial plants (1994)
    Springer
    Photosynthesis research 39 (1994), S. 463-473 
    Details
    ISSN: 1573-5079
    Schlagwort(e): global climate change ; ozone depletion ; photosynthesis ; Photosystem II ; productivity ; UV-B radiation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The photosynthetic apparatus of some plant species appears to be well-protected from direct damage from UV-B radiation. Leaf optical properties of these species apparently minimizes exposure of sensitive targets to UV-B radiation. However, damage by UV-B radiation to Photosystem II and Rubisco has also been reported. Secondary effects of this damage may include reductions in photosynthetic capacity, RuBP regeneration and quantum yield. Furthermore, UV-B radiation may decrease the penetration of PAR, reduce photosynthetic and accessory pigments, impair stomatal function and alter canopy morphology, and thus indirectly retard photosynthetic carbon assimilation. Subsequently, UV-B radiation may limit productivity in many plant species. In addition to variability in sensitivity to UV-B radiation, the effects of UV-B radiation are further confounded by other environmental factors such as CO2, temperature, light and water or nutrient availability. Therefore, we need a better understanding of the mechanisms of tolerance to UV-B radiation and of the interaction between UV-B and other environmental factors in order to adequately assess the probable consequences of a change in solar radiation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00014599
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  • 94
    Digitale Medien
    Digitale Medien
    State adaptations in the cyanobacterium Synechcoccus 6301 (PCC): Dependence on light intensity or spectral composition? (1994)
    Springer
    Photosynthesis research 40 (1994), S. 107-117 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; state adaptations ; shade adaptation ; cyanobacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A profile of high light to intense self-shading conditions was constructed using a white light source and cultures of the cyanobacterium Synechococcus 6301; this profile approximates to a natural self-shading gradient of decreasing light intensity and PS II/PS I excitation ratio. Samples of S.6301 were placed along this profile and allowed to state adapt. To separate the effects of light intensity and wavelength on state adaptation, samples were also placed in a shade profile produced by a white light source and neutral density filters. After adaptation, samples were fixed in their resulting state by the addition of glutaraldehyde, and fluorescence measurements were made at 35° C or –160 °C. It is concluded: 1. Under conditions of deep shade (〈5 μmol m−2s−1 PAR) and weak shade (〉200 μmol m−2s−1 PAR), cells adapt to a low PS II fluorescence state (state 2); in moderate shade (20–60 μmol m−2s−1PAR) cells adapt to a high PS II fluorescence state (state 1). We suggest these findings provide evidence for the operation of different factors on the control of state adaptations in cyanobacteria; one set operates at low light and another at high light intensities. 2. Under conditions of self-shading, there is little evidence to support the contention that state adaptations in cyanobacteria are produced by wavelength-dependent changes in the PS II/PS I excitation ratio, instead, it appaers they are produced by changes in the intensity of incident irradiation. 3. The observed fluorescence changes do not appear to involve major changes in the phycobilisome sensitisation of PS II and PS I. Instead, it appears that these changes are effected by alterations in ΦF of PS II (i.e. changes in PS II excitation density caused by alterations in the rate constants controlling spillover to PS I, photochemistry, fluorescence emission or thermal deactivation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019049
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  • 95
    Digitale Medien
    Digitale Medien
    An enzyme and13C-NMR study of carbon metabolism in heliobacteria (1994)
    Springer
    Photosynthesis research 41 (1994), S. 75-88 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; carbon assimilation ; photosynthetic bacteria ; citric-acid cycle ; pyruvate synthase ; fermentation ; heliobacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Heliobacteria are a group of anoxygenic phototrophs that can grow photoheterotrophically in defined minimal media on only a limited range of organic substrates as carbon sources. In this study the mechanisms which operate to assimilate carbon and the routes employed for the biosynthesis of cellular intermediates were investigated in a newHeliobacterium strain, HY-3. This was achieved using two approaches (1) by measuring the activities of key enzymes in cell-free extracts and (2) by the use of13C nuclear magnetic resonance (NMR) spectroscopy to analyze in detail the labelling pattern of amino-acids of cells grown on [13C] pyruvate and [13C] acetate.Heliobacterium strain HY-3 was unable to grow autotrophically on CO2/H2 and neither (ATP)-citrate lyase nor ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBPcase) were detectable in cell-free extracts. The enzyme profile of pyruvate grown cells indicated the presence of a pyruvate:acceptor oxidoreductase at high specific activity which could convert pyruvate to acetyl-Coenzyme A. No pyridine nucleotide dependent pyruvate dehydrogenase complex activity was detected. Of the citric-acid cycle enzymes, malate dehydrogenase, fumarase, fumarate reductase and an NADP-specific isocitrate dehydrogenase were readily detectable but no aconitase or citrate synthase activity was found. However, the labelling pattern of glutamate in long-term 2-[13C] acetate incorporation experiments indicated that a mechanism exists for the conversion of carbon from acetyl-CoA into 2-oxoglutarate. A 2-oxoglutarate:acceptor oxidoreductase activity was present which was also assayable by isotope exchange, but no 2-oxoglutarate dehydrogenase complex activity could be detected. Heliobacteria appear to use a type of incomplete reductive carboxylic acid pathway for the conversion of pyruvate to 2-oxoglutarate but are unable to grow autotrophically using this metabolic route due to the absence of ATP-citrate lyase.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184147
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  • 96
    Digitale Medien
    Digitale Medien
    Spectroscopic evidence for the presence of an iron-sulfur center similar to Fx of Photosystem I inHeliobacillus mobilis (1994)
    Springer
    Photosynthesis research 41 (1994), S. 115-123 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; bacteriochlorophyll ; electron acceptor ; iron-sulfur center ; Photosystem I ; heliobacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Treatment of membranes ofHeliobacillus mobilis with high concentrations of the chaotropic agent urea resulted in the removal of the iron-sulfur centers FA and FB from the reaction center, as indicated by EPR spectra under strongly reducing conditions. In urea-treated membranes, transient absorption measurements upon a laser flash indicated a recombination between the photo-oxidized primary donor P798+ and a reduced acceptor with a time constant of 20 ms at room temperature. Benzylviologen, vitamin K-3 and methylene blue were found to accept electrons from the reduced acceptor efficiently. A differential extinction coefficient of 225–240 mM−1 cm−1 at 798 nm was determined from experiments in the presence of methylene blue. Transient absorption difference spectra between 400 and 500 nm in the presence and absence of artificial acceptors indicated that the electron acceptor involved in the 20 ms recombination has an absorption spectrum similar to that of an iron-sulfur center. This iron-sulfur center was assigned to be analogous to FX of Photosystem I. Our results provide evidence in support of the presence of FX in heliobacteria, which was proposed on the basis of the reaction center polypeptide sequence (Liebl et al. (1993) Proc. Natl. Acad. Sci. USA 90: 7124–7128). Implications for the electron transfer pathway in the reaction center of heliobacteria are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184151
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  • 97
    Digitale Medien
    Digitale Medien
    Molecular organization of bacteriochlorophyll in chlorosomes of the green photosynthetic bacteriumChloroflexus aurantiacus: Studies of fluorescence depolarization accompanied by energy transfer processes (1994)
    Springer
    Photosynthesis research 41 (1994), S. 181-191 
    Details
    ISSN: 1573-5079
    Schlagwort(e): energy transfer ; green bacteria ; photosynthesis ; picosecond spectroscopy ; pigment system ; (Chloroflexus aurantiacus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Examination was made of changes in fluorescence polarization plane by energy transfer in the chlorosomes of the green photosynthetic bacterium,Chloroflexus aurantiacus. Fluorescence anisotropy in the picosecond (ps) time region was analyzed using chlorosomes suspended in solution as well as those oriented in a polyacrylamide gel. When the main component of BChlc was preferentially excited, the decay of fluorescence anisotropy was found to depend on wavelength. In the chlorosome suspension, the anisotropy ratio of BChlc changed from 0.31 to 0.24 within 100 ps following excitation. In the baseplate BChla region, this ratio decreased to a negative value (−0.09) from the initial 0.14. In oriented samples, the degree of polarization remained at 0.68 for BChlc, and changed from 0.25 to −0.40 for the baseplate BChla by excitation light whose electric vector was parallel to the longest axis of chlorosomes. In the latter case, there was a shift from 0.30 to −0.55 by excitation perpendicular to the longest axis. Time-resolved fluorescence polarization spectra clearly indicated extensive changes in polarization plane accompanied by energy transfer. The directions of polarization plane of emission from oriented samples were mostly dependent on chlorosome orientation in the gel but not on that of the polarization plane of excitation light. Orientations of the dipole moment of fluorescence components was consistent with that of absorption components as determined by the linear dichroism (Matsuura et al. (1993) Photochem. Photobiol. 57: 92–97). A model for molecular organization of BChlc anda in chlorosomes is proposed based on anisotropic optical properties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184159
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  • 98
    Digitale Medien
    Digitale Medien
    Evolution of heliobacteria: Implications for photosynthetic reaction center complexes (1994)
    Springer
    Photosynthesis research 41 (1994), S. 285-294 
    Details
    ISSN: 1573-5079
    Schlagwort(e): heliobacteria ; reaction center ; photosynthesis ; 16S rRNA sequence ; cyanobacteria ; Gram-positive bacteria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The evolutionary position of the heliobacteria, a group of green photosynthetic bacteria with a photosynthetic apparatus functionally resembling Photosystem I of plants and cyanobacteria, has been investigated with respect to the evolutionary relationship to Gram-positive bacteria and cyanobacteria. On the basis of 16S rRNA sequence analysis, the heliobacteria appear to be most closely related to Gram-positive bacteria, but also an evolutionary link to cyanobacteria is evident. Interestingly, a 46-residue domain including the putative sixth membrane-spanning region of the heliobacterial reaction center protein shows rather strong similarity (33% identity and 72% similarity) to a region including the sixth membrane-spanning region of the CP47 protein, a chlorophyll-binding core antenna polypeptide of Photosystem II. The N-terminal half of the heliobacterial reaction center polypeptide shows a moderate sequence similarity (22% identity over 232 residues) with the CP47 protein, which is significantly more than the similarity with the Photosystem I core polypeptides in this region. An evolutionary model for photosynthetic reaction center complexes is discussed, in which an ancestral homodimeric reaction center protein (possibly resembling the heliobacterial reaction center protein) with 11 membrane-spanning regions per polypeptide has diverged to give rise to core of Photosystem I, Photosystem II, and of the photosynthetic apparatus in green, purple, and heliobacteria.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02184169
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  • 99
    Digitale Medien
    Digitale Medien
    The photoproduction of superoxide radicals and the superoxide dismutase activity of Photosystem II. The possible involvement of cytochrome b559 (1994)
    Springer
    Photosynthesis research 41 (1994), S. 327-338 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; Photosystem II ; superoxide radical ; superoxide dismutase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In the present study the light induced formation of superoxide and intrinsic superoxide dismutase (SOD) activity in PS II membrane fragments and D1/D2/Cytb559-complexes from spinach have been analyzed by the use of ferricytochrome c (cyt c(III)) reduction and xanthine/xanthine oxidase as assay systems. The following results were obtained: 1.) Photoreduction of Cyt c (III) by PS II membrane fragments is induced by addition of sodium azide, tetracyane ethylene (TCNE) or carbonylcyanide-p-trifluoromethoxy-phenylhydrazone (FCCP) and after removal of the extrinsic polypeptides by a 1M CaCl2-treatment. This activity which is absent in control samples becomes completely inhibited by the addition of exogenous SOD. 2.) The TCNE induced cyt c(III) photoreduction by PS II membrane fragments was found to be characterized by a half maximal concentration of c1/2=10 μM TCNE. Simultaneously, TCNE inhibits the oxygen evolution rate of PS II membrane fragments with c1/2≈ 3 μM. 3.) The photoproduction of O2 − is coupled with H+-uptake. This effect is diminished by the addition of the O2 −-trap cyt c(III). 4.) D1/D2/Cytb559-complexes and PS II membrane fragments deprived of the extrinsic proteins and manganese exhibit no SOD-activity but are capable of producing O2 − in the light if a PS II electron donor is added. Based on these results the site(s) of light induced superoxide formation in PS II is (are) inferred to be located at the acceptor side. A part of the PS II donor side and Cyt b559 in its HP-form are proposed to provide an intrinsic superoxide dismutase (SOD) activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00019410
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  • 100
    Digitale Medien
    Digitale Medien
    Thermoluminescence as a probe of Photosystem II in intact leaves: Non-photochemical fluorescence quenching in peas grown in an intermittent light regime (1994)
    Springer
    Photosynthesis research 41 (1994), S. 371-379 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; chlorophyll fluorescence ; high energy-state quenching ; calcium release
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract We have measured thermoluminescence (TL) and chlorophyll fluorescence from leaves of peas grown under an intermittent light regime (IML) and followed changes in those leaves during greening. IML peas show low variable fluorescence and a certain capacity for reversible non-photochemical quenching. It has been suggested that reversible quenching may be caused by pH-dependent release of Ca2+ from Photosystem II (PS II) (Krieger and Weis (1992) Photosynthetica 27: 89–98). Under conditions in which reversible non-photochemical quenching occurs, a TL band at around 50 °C is observed, in the presence of DCMU, in IML leaves. A band in this temperature range has previously been observed in PS II depleted of Ca2+ (Ono and Inoue (1989) Biochimica et Biophysica Acta 973: 443–449). The 50 °C band disappears upon dark adaptation. In mature leaves, no significant band is seen at 50 °C. It is concluded that, in IML leaves, reversible quenching may be related to the release of Ca2+ from Photosystem II. However, it seems that in the mature system, under most conditions, such release does not contribute significantly to quenching
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02183039
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