Leaf photosynthesis is resistant to a mild drought stress (Review)
1992
Cornic, G. | Ghashghaie, J. | Genty, B. | Briantais, J.M. (Universite de Paris 11, Orsay (France))
When a terrestrial plant is subjected to a mild drought stress, the leaf net CO2 uptake declines as a result of the stomatal closure. In contrast to previous beliefs the photosynthetic apparatus is very resistant to dehydration. Particularly the relations between photochemistry, its regulation and leaf CO2 assimilation are identical when F is changed either by increasing leaf water deficit or by decreasing the ambient CO2 concentration. When the stomata close in a leaf under water deficit the CO2 concentration within the leaf declines. As a result photorespiration is favoured, the photochemical yield of open photosystem 2 (PS 2) centres and the activity of some enzymes decline (sucrose-phosphate synthase, nitrate reductase). The decline of photochemical yield of PS 2 is consequential to an increase in thermal dissipation of the excitons trapped by PS 2 units. The decline in CO2 concentration occurring in a desiccating leaf may trigger an integrated response of leaf metabolism which still remains to be explored.
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