Continuous Chlorophyll Fluorescence and Gas Exchange Measurements as A New Approach to Study Water Stress Effects on Leaf Photosynthesis

Abstract

Water stress leads to limitations in leaf carbon assimilation, which involves an excess of excitation energy at the level of photosystems reaction centres promoting down-regulation mechanisms of electron transport (1, 2). Thus, parallel decreases in both CO2 assimilation (A) and electron transport rate (ETR) can be expected and, in consequence, it seems possible to detect water stress from chlorophyll fluorescence measurements. Moreover, it has been reported that water stress induces marked effects on steady-state chlorophyll fluorescence (Fs) daily pattern (3,4). In water-stressed grapevines significant reduction of ETR has been found, although such reduction was lower than that of A, suggesting an increase in alternative ways for electron consumption (4).