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  • 1
    Electronic Resource
    Electronic Resource
    Seasonal patterns of tissue water relations in three Mediterranean shrubs co-occurring at a natural CO2 spring (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Seasonal changes in tissue water relations of Erica arborea L., Myrtus communis L. and Juniperus communis L., grown in a Mediterranean environment, were analysed under field conditions over a 12 month period by comparing plants grown in the proximity of a natural CO2 spring (about 700 μmol mol−1 atmospheric CO2 concentration, [CO2]) with plants in ambient conditions. Tissue water relations varied in response to changes in water availability, but the seasonal course of tissue water relations parameters was also related to ontogeny. Tissue water relations of these co-occurring shrubs were not alike. Osmotic potentials and saturated mass/dry mass ratio were lowest during peak drought stress periods. Diurnal changes in osmotic potential at the point of turgor loss were least early in the season, maximal in mid-season, and decreased again in autumn. Turgor potentials decreased as drought progressed and were highest in late fall and mid-winter. Symplastic water fraction was highest in mid-spring for E. arborea and M. communis and decreased during the summer, while the opposite was observed for J. communis. Common to all species, under elevated [CO2], was an increase of turgor pressure, particularly during the summer months. Other parameters showed species-specific responses to long-term elevated [CO2]. In particular, exposure to elevated [CO2] increased osmotic potentials in E. arborea under drought, while the opposite was the case for J. communis. Site differences in predawn to midday shifts were not strong in any of the species. Differences in tissue water relations suggest that the coexistence of these shrubs in the same environment with similar water availability are partially based on differential water relations strategies and water use patterns. Regardless of the mechanisms, growth of these shrubs in elevated [CO2] may be either less, similarly or more affected by drought stress than plants in ambient [CO2] depending on the species and season.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00645.x
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  • 2
    Electronic Resource
    Electronic Resource
    C4 photosynthesis in Cyperus longus L., a species occurring in temperate climates (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 4 (1981), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Cyperus longus L., which has a widespread but disjunct distribution throughout Europe and extends northwards into Britain, was found to be a C4 species based upon its Kranz leaf anatomy, low CO2 compensation point and the labelling of malate as an early product of 14CO2 fixation. The photosynthetic characteristics of C. longus are similar to many other C4 species with a high maximum rate of photosynthesis (〉 1.5 mg CO2 m −2 s −1) and a relatively high temperature optimum (30–35°C), but unlike many C4 species the rate of photosynthesis does not decline rapidly below the optimum temperature and a substantial rate (0.6 mgCO2 m−2s−1)occursat 15°C. Leaf extension is very slow at 15°C and shows a curvilinear response to temperatures between 15 and 25°C. Leaves extend at a rate of almost 4 cm d−1 at 25°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1981.tb01038.x
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  • 3
    Electronic Resource
    Electronic Resource
    Sward growth under cutting and continuous stocking managements: sward canopy structure, tiller density and leaf turnover (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 37 (1982), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The change in structure of continuously grazed versus infrequently cut swards of perennial ryegrass (Lolium perenne L), cv. S23, was investigated during their first full harvest year. Measurements were made from early May until late September. The intensity of stocking by sheep in the grazed sward was adjusted in an attempt to maintain a high level of radiation interception and the cut sward was harvested at approximately monthly intervals.The herbage mass, lamina area index and radiation interception of the cut sward varied in a cyclic pattern between harvests but in the grazed sward these parameters showed considerably less variation, although they all increased early in the season and then declined later. The proportion of dead material above ground increased throughout the season in both sward types but was more marked in the grazed sward.There were major differences between the grazed and cut swards in the number of tillers per unit ground area; the difference became more marked throughout the season and by September the tiller densities in the grazed and cut swards were 3·204 m-2 and 6·203 m-2 respectively. Divergence in tiller density was associated with differences in specific stem weight and leaf area per tiller.Rates of appearance and death of leaves on tillers in the grazed sward were determined. During May, leaf appearance exceeded leaf death but this was reversed in June. During the rest of the season as a new leaf appeared on a tiller so the oldest leaf died.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1982.tb01578.x
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of vernalization on the subsequent rates of leaf extension and photosynthesis of perennial ryegrass (Lolium perenne L.) (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Grass and forage science 42 (1987), S. 0 
    Details
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Temperature and daylength treatments have been used to investigate the apparent link between the potential for rapid leaf extension in spring and floral initiation and development in Lolium perenne (cv. Vigor). After growth at 5°C for 10 weeks (vernalization treatment) the leaves which developed at 15°C expanded significantly faster than non-vernalized controls under both long and short days. Under long days floral development was initiated in vernalized plants but under short days it was not. Specific leaf area was higher in vernalized than non-vernalized plants under long days.The photosynthetic capacity of leaves which developed on plants which had been previously vernalized and then grown at 15°C under long days was higher than non-vernalized controls when expressed on a leaf area and dry weight basis, but not on the basis of chlorophyll content. Vernalization followed by short days resulted in a smaller and non-significant increase in the photosynthetic capacity of leaves.Application of gibberellic acid (GA) as a spray to non-vernalized plants did not affect floral development but did increase the rate of leaf extension. The application of GA did not affect specific leaf area or photosynthetic capacity expressed on an area basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2494.1987.tb02087.x
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  • 5
    Electronic Resource
    Electronic Resource
    Synergistic effects of salinity, temperature and heavy metals on mortality and osmoregulation in marine and estuarine isopods (Crustacea) (1975)
    Springer
    Marine biology 30 (1975), S. 13-20 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effects of cadmium (3CdSO4·8H2O), zinc (ZnSO4·7H2O) and lead [Pb (NO3)2] on mortality, and cadmium, zinc and mercury (HgCl2) on osmoregulation, have been recorded for marine and estuarine species of isopods (Crustacea). The marine species studied were Idotea baltica, I. neglecta, I. emarginata and Eurydice pulchra, which were adapted to 100, 80, 60 and 40% sea water (SW) (100% SW э 34‰ S). The estuarine species used were Jaera albifrons sensu stricto and J. nordmanni, which were adapted to 100, 50, 10 and 1% SW. Both groups of isopods have low mortalities in 100% SW with 10 and 20 ppm of cadmium, zinc and lead, but a decrease in salinity caused an increase in the toxicities of these metals and reduced the LT50 values (time, in hours, to 50% mortality). Mortalities at 10°C were generally higher than those recorded at 5°C. Cadmium had no significant effect on the osmoregulation of I. baltica and I. emarginata in 100 and 80% SW at 5°C, but this metal significantly lowered the blood osmotic concentration of I. neglecta in 80% SW. Zinc did not alter the haemolymph osmotic concentration of I. neglecta in 100 and 80% SW, but significantly lowered the blood osmotic concentration of I. baltica in 100% SW. Cadmium, zinc and mercury also significantly altered the osmoregulatory ability of J. albifrons in dilute saline.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00393748
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of leaf age on leaf resistance and CO2 exchange of the CAM plant Bryophyllum fedtschenkoi (1975)
    Springer
    Planta 123 (1975), S. 91-96 
    Details
    ISSN: 1432-2048
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Leaves of different ages from the CAM (Crassulacean acid metabolism) plant Bryophyllum fedtschenkoi Hamet et Per. differ in their ability to accumulate titratable actidity during the night. Measurements of leaf resistance to water vapour diffusion and net CO2 exchange during the day and night show differing patterns of behaviour dependent upon leaf age. Young leaves do not exhibit CAM; they behave like typical mesophytes with low resistances and a net uptake of CO2 during the day and a net output of CO2 at night. Mature leaves exhibit CAM and have high leaf resistances during the day and lower resistances at night but their pattern of CO2 exchange is complex, with a net output early in their day followed by a net uptake which continues at a reduced rate through the night. Intermediate, leaves are intermediate in their behaviour The presence of CAM in older leaves may simply be the result of increased cell vacuole size. Leaf resistance measurements are discussed in relation to the possible control of stomatal opening by substomatal CO2 concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00388063
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  • 7
    Electronic Resource
    Electronic Resource
    The diurnal course of plant water potential, stomatal conductance and transpiration in a papyrus (Cyperus papyrus L.) canopy (1984)
    Springer
    Oecologia 63 (1984), S. 252-255 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The diurnal course of water potential, stomatal conductance and transpiration was measured on mature umbels (the major evaporating surface) of papyrus (Cyperus papyrus L.) growing in a fringing swamp on Lake Naivasha, Kenya. Umbel water potential declined only slightly during the morning but fell rapidly after midday to a minimum value of-1.5 M Pa in early afternoon. The two main structures forming the umbels, the bracteoles and rays, showed similar patterns of change of stomatal conductance throughout the day. The values of conductance indicate major stomatal opening during the morning, partial midday closure and some recovery of opening during the afternoon. It appears that the increase in water vapour pressure deficit of the air is the major cause of the midday closure of the stomata and that plant water potential has little effect. The reason why transpiration is reduced at high vapour pressure deficits when water is freely available to the roots is not clear. However, it is speculated that the restricted water movement into the plant from the anaerobic root environment has the effect of reducing the uptake of toxic ferrous iron. The daily total of canopy transpiration is estimated to be 12.5 mm, twice the value previously reported for papyrus but similar to daily valus determined for other wetland communities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379885
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  • 8
    Electronic Resource
    Electronic Resource
    The photosynthetic characteristics of papyrus in a tropical swamp (1987)
    Springer
    Oecologia 71 (1987), S. 355-359 
    Details
    ISSN: 1432-1939
    Keywords: Cyperus papyrus ; CO2-Assimilation ; Stomatal response ; Quantum yield ; Humidity response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Photosynthesis and transpiration was measured in the large emergent C4 sedge Cyperus papyrus (papyrus) which occupies wide areas of wetland on the African continent. The maximum observed value of net assimilation was 35 μmol CO2 m-2 s-1 at full sunlight but light saturation of photosynthesis did not occur. The quantum yield of photosynthesis obtained from the initial slope of the light response curves (0.06 mol mol-1 incident light) was relatively high and close to previously recorded values for some C4 grasses. Measurements made over two days showed that stomatal conductance was sensitive to the ambient air vapour pressure deficit (VPD) and was consistently lower on the day when VPD's were higher. There was, however, no marked midday closure of the stomata. Photosynthesis was also reduced on the day when VPD's were higher. The relationship between net photosynthesis and stomatal conductance was close to linear over the range of measurement conditions, with the result that intercellular CO2 concentrations (C i ) did not vary markedly. There was some evidence that C i decreased at high VPD's. The regulation of stomatal movement in papyrus appears to minimise excessive water loss while not severely limiting photosynthesis. The significance of this strategy for a wetland species with plentiful supplies of water is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378707
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  • 9
    Electronic Resource
    Electronic Resource
    Simple molecular method to distinguish the identity of Calanus species (Copepoda: Calanoida) at any developmental stage (1999)
    Springer
    Marine biology 133 (1999), S. 91-96 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Diagnostic morphological characteristics of copepods of the genus Calanus are restricted largely to minor variations in secondary sex characteristics. This presents a persistent problem in the identification of individuals to species level, especially for immature stages. We have developed a simple molecular technique to distinguish between the North Atlantic Calanus species (C. helgolandicus, C. finmarchicus, C. glacialis and C. hyperboreus) at any life stage. Using the polymerase chain-reaction (PCR), the mitochodrial large subunit (16S) ribosomal RNA (rRNA) gene was amplified from individual copepods preserved in ethanol. Subsequent digestion of the amplified products with the restriction enzymes DdeI and VspI, followed by electrophoretic separation in 2% agarose (Metaphor, FMC Ltd), produced a characteristic pattern for each species. The versatility of the method is demonstrated by the unambiguous identification to species of any life stage, from egg to adult, and of individual body parts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050446
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  • 10
    Electronic Resource
    Electronic Resource
    Respiratory responses of the estuarine mysid Neomysis integer (Peracarida: Mysidacea) in relation to a variable environment (1999)
    Springer
    Marine biology 133 (1999), S. 643-649 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The euryhaline mysid Neomysis integer (Peracarida: Mysidacea) is a common member of the hyperbenthos of the upper reaches of European estuaries. In the East Looe River Estuary (Cornwall, England), this species experiences extensive tidal and seasonal changes in temperature (3 to 15 °C) and salinity (1 to 34‰). In this investigation, the effects of temperature (5, 10 and 15 °C) and salinity (1, 10, 20 and 30‰) on the oxygen consumption of male and female N. integer are reported, and are related to field measurements to identify the adaptive responses of the respiratory physiology to such a variable environment. The general responses were similar for each sex; however, at any given temperature/salinity combination, male N. integer consumed more oxygen than females. The general trends were increased oxygen consumption with increasing temperature (Q10 values ranged from ∼1.7 to 2.5) and decreased oxygen consumption with increasing salinity. Temperature and salinity interacted at high water antagonistically to minimise changes in mysid oxygen-consumption. When related to tidal fluctuations in temperature and salinity experienced by N. integer inhabiting the East Looe River Estuary, the results reveal how the respiratory physiology of this species is adapted to its variable environment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002270050504
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