Antioxidant System Activation and Physiological Stability in Lentil under Drought Stress Modulated by Biostimulant Application

In 2023 and 2024, two separate field experiments (split plot with RCBD design) with three replications were conducted to evaluate the effects of 1 mM salicylic acid, humic biostimulant (300 mg/Li), and seaweed (2 Li/ha) on enzyme activities, soluble sugars, anthocyanin content, and physiological traits of lentil (Lens culinaris Medik.) under different irrigation intervals (irrigation after 70, 100, 130, and 160 mm evaporation). Antioxidant enzymes such ascorbate peroxidase, catalase, peroxidase, and polyphenol oxidase increased their activity against free radicals in response to varying degrees of water limitation in lentil plants. While the percentage of ground green cover (PGC), leaf water content (LWC), membrane stability index (MSI), chlorophyll a (Chl a), chlorophyll b (Chl b), and carotenoid content decreased as drought stress increased, the levels of soluble sugar, anthocyanin, and leaf temperature increased. Treatment with biostimulants significantly enhanced all of the traits. Seaweed application significantly increased the levels of carotenoid, PGC, LWC, MSI, and Chl a and b. Improving physiological performance and carbohydrate metabolism with foliar spray of biostimulants also helped lentil plants cope with adverse climatic conditions such as drought stress.