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Physiological responses to flooding in tropical tolerant trees

Abstract:

Flooding of plants inhibits water absorption, causes stomatal closure and reduces photosynthetic rate (A). In tolerant species these physiological responses are reverted with time. In a seasonally flooded forest, we proposed to validate a model to explain the initial responses and the acclimation to flooding. Stomatal closure was apparently produced by an increase in xilematic and leaf content of abscisic acid (ABA). The reduction in stomatal conductance (gs) was accompanied by a diminution in A, diminution in the relative stomatal limitation to photosynthesis (Ls) and increase in the relative mesophyll limitation (Lm). At maximum flood A and gs returned to the values of drained plants. Although a reduction in intercellular [CO2] (Ci) caused by the diminution of A may cause chronic photoinhibition, no decrease in the quantum yield of PSII (Fv/Fm) was observed. Increases of Lm with diminution of Ls suggest that stomatal closure was not the main cause of the reduction of A, which was accompanied by a diminution of soluble protein content, an indirect measure of rubisco content. At maximum flooding, all variables that had suffered changes during rising-waters returned to values of drained trees, indicating acclimation.