Salicylic acid priming enhances low temperature stress tolerance in Egyptian clover (Trifolium alexandrinum L.) by influencing antioxidant system

ABSTRACT

Low temperature is one of the major environmental constraints which reduce plant development and crop productivity. Plants are able to adapt to low-temperature stress through activation of reactive oxygen scavenging systems. Salicylic acid (SA) is one component of a complex signaling pathway modulate the plant responses to environmental stresses including low temperature stress. In this study, we evaluated the effectiveness of salicylic acid (SA) pretreatment on antioxidant system in Egyptian clover under low temperature stress. Antioxidants play important role in enhancing low temperature tolerance in plants. Berseem (var. BL-42 and BL-10) seeds were germinated for three days at 25°C after hydro-priming or SA priming (25, 50, 75, 100 and 125 µg/mL) for 4 hours. After germination of three days, one set of Petri plates was exposed to low temperature (LT) stress (5°C) for five days and other set was retained at 25°C. Physiological and biochemical parameters were observed in root and shoot samples after seven days of germination. Higher vigor index was obtained at 50 and 75 µg/mL of SA pretreatment. Low temperature treatment upregulates antioxidant enzyme (CAT, APX, GR, GPX and SOD) activities but LT+SA treatment further enhanced the antioxidant potential of clover seedlings. SA pretreatment @ 50 to 100 µg/mL concentrations resulted in upregulation of non-enzymatic antioxidants at both 25°C and 5°C. Total protein, proline and total phenol were differentially affected by different SA treatments under LT stress. SA alleviated the adverse effect of LT stress by decreasing lipid peroxidation and H2O2 content in berseem seedlings. Results have shown that SA pretreatment ameliorated LT stress in clover by upregulating antioxidants and biochemical metabolites.