Fluorescence of chlorophyll a and photosynthetic pigments in Atriplex nummularia under abiotic stresses

Chlorophyll a fluorescence is a very useful tool in ecophysiological studies to analyze the photosynthetic performance of plants under biotic and abiotic stresses. This research aimed to evaluate the parameters of the fluorescence of chlorophyll a, contents of chlorophyll a, b and total, and carotenoids in Atriplex nummularia cultivated under water stress (37 and 70% of field capacity) and salt stress (irrigation water with electrical conductivity of 0, 5, 10, 20, 30 and 40 dS m(-1)), besides two sources of salts: NaCl and a mixture of salts of Ca2+, Mg+2, K+, Na+ and Cl-, in a 6 x 2 x 2 factorial, with 4 replicates, totaling 96 experimental plots. At 91 days after transplanting, the initial fluorescence (F-0), maximum fluorescence (F-m), potential quantum efficiency of photosystem II (F-v/F-m), F-v/F-0 ratio and the contents of chlorophyll a, b, and total and carotenoids were determined. All assessed parameters decreased as a standard response to salt stress, except F-0, which had, as a characteristic, the increase in its values under stress conditions. The emission parameters for Atriplex nummularia varied with the type of salt present in the irrigation water.