Photosynthetic responses of hydroponically grown basil ( Ocimum basilicum L.) to drought and high-EC stress

Background: family, is particularly vulnerable to various environmental stressors. This study examines how water deficit and elevated nutrient-solution electrical conductivity (EC) affect the photosynthetic efficiency of basil plants grown in an nutrient film technique (NFT) hydroponic system. Methods: Chlorophyll fluorescence was assessed using both continuous-excitation and modulated pulse-amplitude-modulated (PAM) techniques. Fluorescence parameters were monitored in plants at two developmental stages, immature and mature, under drought and high-electrical-conductivity (EC) stress. Results: Both stressors altered Photosystem II (PSII)-related fluorescence parameters, but high EC stress caused a wider spectrum of changes. In mature plants, those alterations were less pronounced, indicating enhanced tolerance likely due to more efficient electron transport and greater structural stability of the photosynthetic apparatus. The obtained results supported our hypothesis, that drought and high-EC stress would differentially impair photosynthetic efficiency, with drought imposing stronger osmotic limitations on photochemistry and high EC introducing additional ionic constraints. These stresses generated distinct physiological response patterns detectable by chlorophyll fluorescence measurements.