Authors: Malcolm Possell C Nicholas Hewitt
Publish Date: 2009/01/04
Volume: 229, Issue: 4, Pages: 837-846
Abstract
The photosynthetic responses of the tropical tree species Acacia nigrescens Oliv grown at different atmospheric CO2 concentrations—from subambient to superambient—have been studied Lightsaturated rates of net photosynthesis A sat in A nigrescens measured after 120 days exposure increased significantly from subambient 196 μL L−1 to current ambient 386 μL L−1 CO2 growth conditions but did not increase any further as CO2 became superambient 597 μL L−1 Examination of photosynthetic CO2 response curves leaf nitrogen content and leaf thickness showed that this acclimation was most likely caused by reduction in Rubisco activity and a shift towards ribulose15bisphosphate regenerationlimited photosynthesis but not a consequence of changes in mesophyll conductance Also measurements of the maximum efficiency of PSII and the carotenoid to chlorophyll ratio of leaves indicated that it was unlikely that the pattern of A sat seen was a consequence of growth CO2 induced stress Many of the photosynthetic responses examined were not linear with respect to the concentration of CO2 but could be explained by current models of photosynthesisWe thank David Beerling University of Sheffield UK for helpful comments on the manuscript G Johnston Lancaster University UK for technical assistance in manufacturing and maintaining the experimental chambers and E Bottoms Centre for Ecology and Hydrology Lancaster UK for assistance with the elemental analyses This work was funded by a Natural Environmental Research Council award NE/E003672/1 and benefited from support from the European Science Foundation “VOCBAS” programme and EU “ISONET” Marie Curie RTN
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