Infodoc : Sciences, Techniques et Culture

Acclimation of fully developed leaves of Bischofia javanica Blume to shadelight was examined. Seedlings were grown under simulated daylight (1000 umol m-2 s-1), then transferred to a simulated shadelight (40 %mol m-2 s-1). When a high-light leaf was transfered to low light, large negative net photosynthetic rates (Pn) were recorded. This decrease was rapid, but within 7 d the rate increased and became equal to the low-light control leaf. These changes in photosynthesis did not follow the pattern of changes in stomatal conductance (gg). Transfer to the low light resulted in a dramtic dcrease in leaf weight per unit area (Lw), and most of the decreases in Lw occured within 3 d of tranfer when the Pn of the transferred leaf was well below that of the low-light control leaf. There was a s[...]

Acclimation of fully developed leaves of Bischofia javanica Blume to shadelight was examined. Seedlings were grown under simulated daylight (1000 umol m-2 s-1), then transferred to a simulated shadelight (40 %mol m-2 s-1). When a high-light leaf was transfered to low light, large negative net photosynthetic rates (Pn) were recorded. This decrease was rapid, but within 7 d the rate increased and became equal to the low-light control leaf. These changes in photosynthesis did not follow the pattern of changes in stomatal conductance (gg). Transfer to the low light resulted in a dramtic dcrease in leaf weight per unit area (Lw), and most of the decreases in Lw occured within 3 d of tranfer when the Pn of the transferred leaf was well below that of the low-light control leaf. There was a significant decrease in chlorophyll a in the transfered leaf without an appreciable change in chlorophyll b resulting in a large decrease in the chlorophyll a to chlorophyll b ratio. Leaf chlorophyll per unit area were higher in the transferred leaf than the low-light control leaf. Maximum photosynthetic rate in the transferred leaf was decreased by 40% compared to that for the high-control leaf, but was almost at the same extent higher than the low-light control leaf. The results are discussed in the context of carbon gain capacity of its seedlings under light-limiting forest understorey habitats. "(Résumé des auteurs)".