Seed priming with humic acid modifies seedling vigor and biochemical response of lentil under heat stress conditions

Lentil (Lens culinaris) is one of the most important cool season pulse crops, which is rich in carbohydrates, proteins, minerals, and fibers. It encounters various abiotic stresses that negatively impacts the crop productivity. With an increasing global average temperature, the effect of heat stress on lentil seed germination needs to be addressed. Seed priming is a cost-effective quality enhancement technique for mitigating abiotic stresses in several crops. Thus, this study was conducted to evaluate the feasibility of priming techniques to mitigate heat stress. Heat stress (30 and 20 degrees C for 16 and 8 h, respectively) hampered seed germination and affected further seedling development in all of the lentil varieties, namely, IPL 316, PDL 1, and L 4147, due to increased membrane leakage and reduced chlorophyll content. Seed priming with humic acid at a concentration of 600 ppm for 18 h increased the germination percentage (20%-23%), seedling vigor (29%-34%), membrane stability index (14%-18%), chlorophyll content (32%-68%), proline content (55%-68%), phenolic content (30%-31%), catalase activity (49%-61%), peroxidase activity (54%-64%), superoxide dismutase content (40%), total soluble sugar content (11%-12%), soluble protein (3%-8%), and free amino acid content (5%-10%), and reduced the mean germination time (8%-10%), malondialdehyde (20%-24%), hydrogen peroxide (18%-28%), and carbohydrate (3%-5%) contents in the lentil varieties under heat stress. Humic acid priming fastens the imbibition of water with effective reserve mobilization providing rapid germination. Moreover, seed priming with humic acid in lentil improves the antioxidant machinery and osmoprotection mechanism, which reduces the accumulation of deleterious reactive oxygen species and lipid peroxidation, thereby increasing membrane stability. This suggests the possible protection of plants from the negative consequences of heat stress.