Synergistic effects of glutathione and zinc seed priming in alleviating salt stress on maize seed germination, metabolite levels, seedling vigor, and nutrient acquisition

Abstract

The comparative effects of reduced glutathione (GSH) and 0.5 % Zn (applied separately or in combination) were assessed on maize in relation to seed metabolite levels, seedling growth, antioxidative defense mechanism, levels of biochemicals and nutrient acquisition under NaCl stress. The level of applied salinity was 120 mM in Hoagland's nutrient solution. Salinity negatively affected seed germination and the emergence of seedlings; associated with altered seed metabolic activities. The high salinity also elevated the levels of malondialdehyde (MDA), increased reactive oxygen species (ROS) levels, altered metabolite levels, reduced uptake of mineral nutrients and increased the uptake of Na⁺ in maize seedlings. Interestingly, the GSH seed priming protocol, when applied alone or with Zn, ameliorated the physiological negativities associated with high salinity upon maize germination, emergence and seedling development. The three millimolar GSH concentration in combination with Zn (0.5 %) improved the germination attributes and emergence of seedlings. The GSH level of 3 mM with Zn was also effective in mitigating the negative impacts of NaCl salinity on seedling growth, associated with better maintenance of physio-biochemical activities, reduced uptake or translocation of Na²⁺, and better maintenance of the increased K⁺/Na⁺ and Ca²⁺/Na⁺. The improvement in maize salt stress tolerance, attributed to 3 mM GSH with 0.5 % Zn as seed treatment, was associated with reduced Na⁺ uptake that decreased its toxicity. Based on this study, it is plausible to use a combination of GSH and Zn as seed priming agentsto enhance the physiological resilience of maize growing in areas with high salinity.