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Stomatal and non-stomatal limitations of photosynthesis in trees of a tropical seasonally flooded forest

Abstract:

Trees in the flooded forest of the Mapire River in Venezuela suffer a decrease in photosynthetic rate (A) when flood begins, which is reverted at maximum flood. Changes in A are accompanied by similar changes in stomatal conductance (g<inf>s</inf>), and the possibility of changes in photosynthetic capacity is not ruled out. In order to understand how relative stomatal and non-stomatal limitations of photosynthesis are affected by flooding, we studied the seasonal changes in A and its response to intercellular CO<inf>2</inf> concentration in trees of Campsiandra laurifolia, Symmeria paniculata, Acosmium nitens and Eschweilera tenuifolia. Flooding caused in trees of C. laurifolia and S. paniculata a reduction in A, g<inf>s</inf>, carboxylation efficiency and total soluble protein (TSP), whereas gas exchange in A. nitens and E. tenuifolia was more sensitive to drought. Under flooding, relative stomatal limitation (L<inf>s</inf>) was on average half the highest, and relative non-stomatal limitation (L<inf>ns</inf>) increased from the dry season to flooding. Under full flood, A, g<inf>s</inf> and TSP regained high values. A was positively correlated to light-saturated electron transport rate, suggesting that part of the decrease in A under flooding was due to impairment of photosynthetic capacity. Under flooding, not only stomatal closure but also increased L <inf>ns</inf> causes a reduction in photosynthesis of all four species, and a process of acclimation as flooding progresses allows gas exchange and related variables to regain high values. © Physiologia Plantarum 2008.