Pre-sowing proline seed priming enhances germination, emergence, and antioxidant capacity of pepper under chilling stress

Low temperature stress is a major limiting factor for seed germination and uniform seedling establishment in warm-season crops, particularly during early sowing periods. Exogenous application of osmo-protective compounds is a promising strategy to alleviate the adverse effects of abiotic stress on seed germination and early seedling establishment. Proline, a multifunctional amino acid, plays a key role in osmotic adjustment, membrane protection, and antioxidant defense. This study investigated the effects of pre-sowing proline seed priming on germination and emergence performance of pepper (Capsicum annuum L.) seeds under chilling stress conditions. Pepper seeds were primed with proline solutions at 0 (control), 5, 10, and 15 mM for 24 h, air-dried for 24 h, and subjected to germination and emergence tests under optimum (25 °C) and chilling stress (15 °C) conditions. Germination and emergence traits were assessed together with biochemical parameters, including thiobarbituric acid reactive substances (TBARS), hydrogen peroxide (H₂O₂) content, antioxidant enzyme activities, total chlorophyll content, and endogenous proline levels. Chilling stress significantly reduced germination and emergence in untreated seeds. Proline priming markedly mitigated these negative effects, with 15 mM proline resulting in the highest germination and emergence percentages under chilling stress. Proline-treated seedlings exhibited lower TBARS and H₂O₂ levels, indicating reduced oxidative damage, along with enhanced antioxidant enzyme activities, total chlorophyll content, and endogenous proline accumulation. Pre-sowing proline priming effectively improves pepper seed germination and emergence under chilling stress by strengthening antioxidant defense and reducing lipid peroxidation.