Fluorescence emission and photochemical yield of parsley under saline waters of different cationic nature

•Parsley has good development in various saline scenarios under hydroponics.•Fluorescence and photochemical yield are compromised by the nature of salts.•Replenishment with public-supply water mitigates the deleterious effects of salinity.•The higher the concentration of salts, the more evident is the effect of cationic nature. Chlorophyll fluorescence is a non-destructive analysis tool to diagnose the effects of salinity on the photosynthetic apparatus and photochemical yield. The present study aimed to evaluate the photochemical yield of parsley plants, exposed to increasing levels of electrical conductivity of nutrient solutions (1.7; 2.7; 3.7; 4.7; 5.7 and 6.7 dS m−1) formulated in waters with NaCl, CaCl2, MgCl2 and KCl. The mode of water replenishment in hydroponic system was also evaluated. For this, two experiments were conducted, maintaining the same experimental configuration, and varying the water replenishment. The nutrient solution, whose volume decreases with the consumption by plants, was replenished using a public-supply water (Experiment I) and the respective saline water used to prepare the nutrient solution (Experiment II). The following parameters were evaluated: initial (Fo), maximum (Fm) and variable (Fv) fluorescence; quantum (Fv/Fm) and maximum (Fo/Fm) yield of photosystem II; and also the quantum yield of electron transport (φEo), flux absorption (ABS/RC), flux transport (ETo/RC) and dissipated energy (DIo/RC) per reaction center for the two experiments. It was concluded that replenishment with public-supply water causes less damage to chlorophyll variables and quantum yields as the nutrient solution electrical conductivity increases than replenishment with saline water, whereas on variables related to electron transfer, such effect was not noticeable. Plants cultivated under NaCl had higher tolerance to salt stress compared to other cations.