Hydrogen peroxide priming alleviates salinity induced toxic effect in maize by improving antioxidant defense system, ionic homeostasis, photosynthetic efficiency and hormonal crosstalk.

Abstract

Salinity stress (SS) is a serious detrimental factor for crop growth and productivity and its intensity it is continuously increasing which is posing serious threat to global food security. Hydrogen peroxide (H2O2) priming has emerged as an excellent strategy to mitigate the adverse impacts of SS. However, the role of H2O2 priming in mitigating the salinity induced toxicity is not fully explored. Therefore, in this context the present study was conducted in complete randomized design (CRD) in factorial combination to determine the impact of H2O2 priming on germination, growth, physiological and biochemical traits, osmo-regulating compounds, hormonal balance and ionic homeostasis. The experiment was based on different levels of SS; control, 6 and 12dSm-1 SS and priming treatments, control and H2O2 priming (2%). Salinity stress significantly reduced the growth, leaf water status (- 15.55%), calcium (Ca2+), potassium (K+) and magnesium (Mg2+) accumulation and increased malondialdehyde(MDA: + 29.95%), H2O2 (+ 21.48%) contents, osmo-regulating compounds (proline, soluble sugars), indole acetic acid (IAA), anti-oxidant activities (ascorbate peroxidase: APX, catalase: CAT, peroxidase: POD and ascorbic acid: AsA) and accumulation of sodium (Na+) and chloride (Cl-.). H2O2 priming effectively reduced the effects of SS on germination and growth and strengthen the anti-oxidant activities through reduced MDA (- 12.36%) and H2O2 (- 21.13%) and increasing leaf water status (16.90%), soluble protein (+ 71.32%), free amino acids (+ 26.41%), proline (+ 49.18%), soluble sugars (+ 71.02%), IAA (+ 57.59%) and gibberlic acid (GA) (+ 21.11%). Above all, H2O2 priming reduced the massive entry of noxious ions (Na+ and Cl-) while increased the entry of Ca2+, K+ and Mg2+ thus improved the plant performance under SS. In conclusion H2O2 priming was proved beneficial for improving maize growth under SS thorough enhanced anti-oxidant activities, photosynthetic pigments, leaf water status, accumulation of osmo-regulating compounds, hormonal balance and ionic homeostasis.