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  • 1
    Electronic Resource
    Electronic Resource
    Photosynthetic responses to light in seedlings of selected Amazonian and Australian rainforest tree species (1984)
    Springer
    Oecologia 63 (1984), S. 215-224 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Seedlings of the Caesalpinoids Hymenaea courbaril, H. parvifolia and Copaifera venezuelana, emergent trees of Amazonian rainforest canopies, and of the Araucarian conifers Agathis microstachya and A. robusta, important elements in tropical Australian rainforests, were grown at 6% (shade) and 100% full sunlight (sun) in glasshouses. All species produced more leaves in full sunlight than in shade and leaves of sun plants contained more nitrogen and less chlorophyll per unit leaf area, and had a higher specific leaf weight than leaves of shade plants. The photosynthetic response curves as a function of photon flux density for leaves of shade-grown seedlings showed lower compensation points, higher quantum yields and lower respiration rates per unit leaf area than those of sun-grown seedlings. However, except for A. robusta, photosynthetic acclimation between sun and shade was not observed; the light saturated rates of assimilation were not significantly different. Intercellular CO2 partial pressure was similar in leaves of sun and shade-grown plants, and assimilation was limited more by intrinsic mesophyll factors than by stomata. Comparison of assimilation as a function of intercellular CO2 partial pressure in sun- and shade-grown Agathis spp. showed a higher initial slope in leaves of sun plants, which was correlated with higher leaf nitrogen content. Assimilation was reduced at high transpiration rates and substantial photoinhibition was observed when seedlings were transferred from shade to sun. However, after transfer, newly formed leaves in A. robusta showed the same light responses as leaves of sun-grown seedlings. These observations on the limited potential for acclimation to high light in leaves of seedlings of rainforest trees are discussed in relation to regeneration following formation of gaps in the canopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00379880
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  • 2
    Electronic Resource
    Electronic Resource
    Control of photosynthesis by the carbohydrate level in leaves of the C4 plant Amaranthus edulis L. (1989)
    Springer
    Planta 177 (1989), S. 515-525 
    Details
    ISSN: 1432-2048
    Keywords: Amaranthus ; Carbohydrate accumulation ; Chilling treatment ; Sucrose inhibition of photosynthesis ; Phloem translocation ; Photosynthesis (C4 plant)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis was studied in relation to the carbohydrate status in intact leaves of the C4 plant Amaranthus edulis. The rate of leaf net CO2 assimilation, stomatal conductance and intercellular partial pressure of CO2 remained constant or showed little decline towards the end of an 8-h period of illumination in ambient air (340 μbar CO2, 21% O2). When sucrose export from the leaf was inhibited by applying a 4-h cold-block treatment (1°C) to the petiole, the rate of photosynthesis rapidly decreased with time. After the removal of the cold block from the petiole, further reduction in photosynthetic rate occurred, and there was no recovery in the subsequent light period. Although stomatal conductance declined with time, intercellular CO2 partial pressure remained relatively constant, indicating that the inhibition of photosynthesis was not primarily caused by changes in stomatal aperture. Analysis of the leaf carbohydrate status showed a five- to sixfold increase in the soluble sugar fraction (mainly sucrose) in comparison with the untreated controls, whereas the starch content was the same. Leaf osmotic potential increased significantly with the accumulation of soluble sugars upon petiole chilling, and leaf water potential became slightly more negative. After 14 h recovery in the dark, photosynthesis returned to its initial maximum value within 1 h of illumination, and this was associated with a decline in leaf carbohydrate levels overnight. These data show that, in Amaranthus edulis, depression in photosynthesis when translocation is impaired is closely related to the accumulation of soluble sugars (sucrose) in source leaves, indicating feedback control of C4 photosynthesis. Possible mechanisms by which sucrose accumulation in the leaf may affect the rate of photosynthesis are discussed with regard to the leaf anatomy of C4 plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392620
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Nitrogen supply as a factor influencing photoinhibition and photosynthetic acclimation after transfer of shade-grown Solanum dulcamara to bright light (1986)
    Springer
    Planta 168 (1986), S. 563-570 
    Details
    ISSN: 1432-2048
    Keywords: Nitrogen nutrition and photosynthesis ; Photoinhibition of photosynthesis ; Photosynthesis (acclimation) ; Solanum (photosynthetic acclimation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have compared the ability of shadegrown clones of Solamum dulcamara L. from shade and sun habitats to acclimate to bright light, as a function of nitrogen nutrition before and after transfer to bright light. Leaves of S. dulcamara grown in the shade with 0.6 mM NO 3 - have similar photosynthetic properties as leaves of plants grown with 12.0 mM NO 3 - . When transferred to bright light for 1–2 d the leaves of these plants show substantial photoinhibition which is characterized by about 50% decrease in apparent quantum yield and a reduction in the rate of photosynthesis in air at light saturation. Photoinhibition of leaf photosynthesis is associated with reduction in the variable component of low-temperature fluorescence emission, and with loss of in-vitro electron transport, especially of photosystem II-dependent processes. We find no evidence for ecotypic differentiation in the potential for photosynthetic acclimation among shade and sun clones of S. dulcamara, or of differentiation with respect to nitrogen requirements for acclimation. Recovery from photoinhibition and subsequent acclimation of photosynthesis to bright light only occurs in leaves of plants provided with 12.0 mM NO 3 - . In these, apparent quantum yield is fully restored after 14 d, and photosynthetic acclimation is shown by an increase in light-saturated photosynthesis in air, of light-and CO2-saturated photosynthesis, and of the initial slope of the CO2-response curve. The latter changes are highly correlated with changes in ribulose-bisphosphate-carboxylase activity in vitro. Plants supplied with 0.6 mM NO 3 - show incomplete recovery of apparent quantum yield after 14 d, but CO2-dependent leaf photosynthetic parameters return to control levels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00392277
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    Paper (German National Licenses)
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