Enzymatic and biochemical responses to high temperatures and drought stress during the reproductive stage in lentil (Lens Culinaris Medik.)

Increasing temperatures and drought stress are two major factors limiting lentil (Lens culinaris Medik.) productivity, particularly during reproductive stage. The current research aimed to determine the response of lentil genotypes with varying heat and drought sensitivity. For this purpose, twelve genotypes were evaluated under high temperature stress (> 32°C), while seven genotypes were investigated under drought stress conditions during the reproductive stage (75% field capacity). Under stress conditions, the results revealed significant variation in enzymatic responses between tolerant and susceptible genotypes. Under high temperature and drought stress, tolerant genotypes accumulated higher concentrations of catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD), whereas susceptible genotypes had low enzymatic responses. Proline content (PC) increased significantly with high temperature and drought stress in tolerant genotypes, but not in susceptible genotypes. Because of high temperature and drought stress, the concentrations of total antioxidant activity (TAA), total phenolic content (TPC), tannins (TC), and total flavonoids (TFC) increased significantly in tolerant genotypes compared to susceptible genotypes. Furthermore, when tolerant genotypes were stressed, there were significant increases in total soluble sugars (TSS) and reducing sugars (RS) compared to normal conditions. Our results indicated that SOD had significant positive correlation with TAA, TC, PC and RS under high temperature, while it was correlated with CAT, TC, TAA under drought conditions. Highly significant correlation was also observed between CAT and AOP under both stressed conditions. Tolerant genotypes that responded better to high temperature and drought stress may be able to maintain physiological processes and generate high yield potential.