Gas exchanges and photochemical efficiency of hydroponic bell pepper under salinity and plant density

ABSTRACT Gas exchanges and chlorophyll a fluorescence are ways to physiologically analyze the response of plants to salt stress. In this context, the present work was conducted between August and November 2016 in a greenhouse at the Federal University of Campina Grande (7°12’52” S, 35°54’24” W, mean altitude of 550 m), using bell pepper plants cv. All Big, exposed to levels of nutrient solution electrical conductivity (1.7, 3.7, 5.7, 7.7, 9.7 and 11.7 dS m-1) and cultivated in hydroponic system, spaced by 0.2 and 0.3 m, focusing on the analysis of gas exchanges and photochemical efficiency. The experimental design was completely randomized, in a 6 x 2 factorial scheme, with five replicates. Plant density influenced the sensitivity of the gas exchanges to salinity and, when reduced, mitigated its effects at higher salinity levels. Increasing plant density at high levels of electrical conductivity caused damage to the photosynthetic apparatus and even reduced the levels of efficiency of the photosystem II from 3.98 dS m-1