Assessment Effect of Water Deficit Stress and Foliar Application of Zinc Sulfate on Seed yield, Grain Protein and Antioxidant Enzymes

BACKGROUND: Microelements are inorganic compounds involved in the synthesis of enzymes and biologically active substances. OBJECTIVES: To evaluate the physiological traits of maize to ZnSO4 and FeSO4 under drought stress, a field experiment was conducted on maize plants grown under different soil moistures and treated with foliar ZnSO4 and FeSO4 applications. METHODS: The experiment was laid out as split-split plot in a randomized complete block design with three replicates. The main plot consisted of three levels of water deficit stress comprised of complete irrigation (control), no irrigation at vegetative growth stage (12-14 leaf), and no irrigation at early seed growth stage. Water deficit stress treatment was specific to the above-mentioned stages, after which and until the end of the growth period, the water requirement of the plant was fulfilled. The sub-plot contained foliar solution of zinc sulfate at three concentrations (0, 5 and 10 gr.l-1) and sub-sub-plot included iron sulfate foliar solution at three concentrations (0, 3 and 6 gr.l-1). RESULT: Drought stress especially at early seed growth stage significantly decreased grain yield, and Fv/Fm ratio but, activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione reductase (GR) under drought stress were increased. Foliar applied ZnSO4 and FeSO4 increased grain yield by 15.22, 10.73 and 10.74% under normal irrigation, no irrigation at vegetative growth stage and no irrigation at early seed growth stage, respectively. Also further increased the antioxidant enzyme activities and enhanced total phenol content of maize under drought stress. Combined application of ZnSO4 and FeSO4 resulted in alleviating maize plant drought stress by Zn and Femediated improvement in photosynthetic gas exchange attributes. Besides the foliar application of ZnSO4 and FeSO4 regulated physiological processes in maize plants and alleviated the adverse effects of water stress. Results showed that ZnSO4 and FeSO4 could be used for improving maize growth under drought stress. CONCLUSION: The highest grain yield of maize was recorded for non-drought stress treatment and was followed by foliar application of both ZnSO4 and FeSO4, while severe water stress and non-application of Zn and Fe resulted in the minimum grain yield.