Exogenous application of glutathione induces wheat tolerance to heavy metal stress by modulating the antioxidative enzymatic defenses

Abstract

Heavy metal stress destroys plants growth and yield. Glutathione (GSH) is a well-known antioxidant that promotes plant growth by protecting it from abiotic stresses including heavy metal toxicity. Although much has been documented about the role of glutathione in securing plants from stress, its role in safeguarding wheat growth under mercury (Hg) and arsenic (As) stresses is unknown. The present work investigates wheat responses to Hg and As stresses under the exogenous application of GSH. The result showed that Hg and As stresses greatly reduced seed germination and seedling growth such as root/shoot length and fresh weight. Photosynthetic pigments, i.e., chlorophyll a, b, and carotenoid were reduced. However, the H₂O₂ and lipid peroxidation levels were increased under Hg and As stresses in wheat seedlings. The antioxidant enzymatic activities such SOD, POD, and APX increased, while CAT activity decreased under Hg and As stresses. Importantly, the application of 2 mM GSH alone or in combination with Hg and As enhanced seed germination rate, root/shoot length, fresh weight, and photosynthetic pigments in wheat. Contrarily, the level of H₂O₂ and lipid peroxidation were decreased under the individual and combined treatment of Hg + GSH and As + GSH. The antioxidant enzymatic activities such as SOD, POD, and APX were lowered, while CAT activity was enhanced by GSH under Hg and As stress. The present research concludes that supplementation of exogenous GSH can play a significant role in fostering the sensitivity of wheat to Hg and As stress by reducing oxidative stress and modulating the levels of antioxidant enzymes.