Sequenced application of glutathione as an antioxidant with an organic biostimulant improves physiological and metabolic adaptation to salinity in wheat

Abstract

Globally, salinity threatens the agricultural crops productivity by inhibiting plant growth and development through osmotic stress and ionic cytotoxicity. The polygenic nature of salinity offers several pragmatic shotgun approaches to improve salinity tolerance. The present study investigated the potential of glutathione (GSH; 1 mM) as an antioxidant and moringa leaf extract (MLE; 3%) as an organic biostimulant applied in sequence as seed priming and foliar spray on wheat growth, physiology and metabolic adaptation under saline conditions (9.16 dS m^-1). Plants without any treatment and water spray (H₂O) were considered controls. Salinity induced osmotic stress reduced the plant tissue water status and photosynthetic performance, and perturbed ionic (K⁺/Na⁺, Ca²⁺/Na⁺, K⁺+Ca²⁺/Na⁺) and hormonal (IAA, GA₃, zeatin, ABA) homeostasis, consequently affected growth and yield in wheat. Sequenced applied MLE and/or GSH improved osmotic stress tolerance by stabilizing membrane integrity and decreasing electrolyte leakage. These positive results were owed to enhanced endogenous GSH and ascorbate levels. Improved tissue water status was attributed to increased osmotic adjustment, better ionic and hormonal homeostasis contributed to improving photosynthetic efficiency and growth under salinity. Exogenously applied MLE and GSH sequences improved grain yield, which was attributed to the maintenance of green leaf area and delayed senescence associated with an increase in photosynthetic pigments and chlorophyll fluorescence traits. In crux, exogenous applied MLE and/or GSH can be the best physiological strategy to reduce the deleterious effects of salinity and improve physiological and metabolic adaptation in wheat under saline field conditions.

Keywords: Antioxidants; Delayed senescence; Ionic homeostasis; Osmotic stress; Photosynthetic efficiency.