Pretreatment with selenium and zinc modulates physiological indices and antioxidant machinery to improve drought tolerance in maize (Zea mays L.)

Abstract Selenium (Se) and zinc (Zn) are known for their nutritional importance in biological systems. In plants, exogenous supply of these nutrients has beneficial effects on growth and development particularly under environmental stress conditions. The present study examined the effects of Zn and Se seed priming on germination and seedling growth of maize (Zea mays cv. P1574) under drought stress. The seeds were soaked in individual or combined Se (0.075 mM) and Zn (10 mM) solutions for 12 and 24 h using water-primed and un-primed seeds as control. Various priming treatments included HP1 [hydropriming for 12 h], HP2 [hydropriming for 24 h], Se1 [selenium seed priming for 12 h], Se2[selenium seed priming for 24 h], Zn1 [zinc seed priming for 12 h], Zn2 [zinc seed priming for 24 h], (Se + Zn)1[Se + Zn seed priming for 12 h] and (Se + Zn)2[Se + Zn seed priming for 24 h], whereas water stress treatments were kept at 100 (normal) and 60% (drought stress) field capacity. Zn or Se seed treatment significantly increased germination indices (germination percentage [52%], promptness index [54%], vigor index [35%] and emergence index [42%]) and upregulated enzymatic antioxidants such as catalase (69%), guaiacol peroxidase (116%), superoxide dismutase (48%) and ascorbate peroxidase (39%) in maize seedlings raised from Se + Zn primed seeds compared to water and un-primed seeds. Moreover, the primed Se and Zn were efficiently translocated to the shoot resulting in 154 and 114% higher Se and Zn content, respectively by Se + Zn seed priming compared to their individual treatments. These results demonstrate the role of combined Se and Zn seed treatment to improve drought tolerance in maize, which may simultaneously bring about biofortification benefits considering nutritional importance of Se and Zn in human diet.