Gas Exchange and Chlorophyll Fluorescence Responses of Açaí and Juçara Palms Under Salt Stress

The genus Euterpe, which includes açaí palm (Euterpe oleracea) and juçara palm (Euterpe edulis), plays an important socioeconomic and environmental role in Brazil. However, soil and water salinization is a global issue that compromises agricultural productivity by affecting plant physiological and metabolic processes. This study aimed to evaluate the physiological responses of young açaí and juçara plants under salt stress. The experiment was conducted in a randomized complete block design in a 5 × 2 factorial arrangement, consisting of five irrigation water salinity levels (0.1, 1.0, 2.0, 3.0, and 5.0 dS m−1) and two Euterpe species (açaí and juçara), with four replicates. After 104 days of stress exposure, gas exchange, chlorophyll ‘a’ fluorescence, relative chlorophyll index (SPAD), and sodium, chloride, and phenolic compounds were evaluated. Increasing salinity caused linear reductions in the maximum quantum yield and potential photochemical efficiency of PSII, accompanied by an increase in F0/Fm, indicating impaired PSII photochemical performance and photoinhibition. Stomatal conductance and transpiration also decreased significantly with increasing salinity, with reductions of up to 41.33% and 35.48%, respectively, at the highest salinity level. Salt stress negatively affected the physiological performance of both palm species through stomatal limitation and reduced photosystem II efficiency. However, açaí plants exhibited greater tolerance to salt stress than juçara plants.