Efficacy of Zn-Aspartate in comparison with ZnSO4 and L-Aspartate in amelioration of drought stress in maize by modulating antioxidant defence; osmolyte accumulation and photosynthetic attributes

Human population is exceeding beyond the carrying capacity of earth resources and stresses like water shortage faced by the plants is jeopardizing the food security. Current research study was aimed to investigate the potentials of Zn-Aspartate (Zn-Asp), Zn-Sulphate (ZnSO4) and L-Aspartate (L-Asp) to be used as osmolytes and role of various levels of these chemicals in combating drought stress in maize plants in Punjab, Pakistan. Study was performed on two plots corresponding to drought and controlled environments. The lamina of maize plants was sprinkled row wise with various treatments including No spray (NS), water sprinkle (WS), sprinkle with ZnSO4 0.25% and 0.50%, sprinkle with Zn-Asp 0.25% and 0.50% and Foliar sprinkle of L-Asp 0.5% and 1%, respectively. Role of major osmoprotectants and secondary metabolites was analyzed and positive changes were found in total soluble sugars (41.16), flavonoids (5387.74), tocopherol content (9089.18), ascorbic acid (645.27) and anthocyanin (14.84) conc. which assists in mitigating drought menace on maize. Shoot mineral ions (Ca, K, Zn, P, Mg and N) status of water stressed maize plants was also analyzed and it was found that application experimental dose enhanced their availability to crop. Physio-biochemical studies were performed on antioxidants enzymes like superoxide dismutase (SOD), peroxidase (POD), carotenoid content (CC), malondialdehyde, hydrogen peroxide, aspartate and free amino acid contents. The activity of SOD was increased by 28.5% and activity of POD was increased by 33.33% due to foliar applied 0.5% Zn-Asp under drought stress. Photosynthetic pigments (chlorophyll A, B and total chlorophyll content) analysis was also carried out in this study. It was found that conc. of different chlorophylls pigments increased (chl-A: 2.24, chl-B: 25.12, total chl: 24.30) which enhanced photosynthetic activity culminating into better growth and yield). The level of malondialdehyde and hydrogen peroxide decreased by 43.9% and 32.8% respectively on treatment with 0.5% Zn-Asp proving the efficacy of the treatment in drought amelioration. Study reveals that Zn-Asp induced modulations are far better than conventional sulphate salts in mitigating water scarce environment. Current study recommends the use of the Zn-Asp to meet the global food and agricultural challenges as compared to ZnSO4 and L-Asp due to its better drought amelioration properties. This research provides valuable informations which can used for future research and practical use in agriculture fields by indigenous and other people to enhance yield of maize to meet the food necessities of country.