Allicin improves gas exchange characteristics, redox balance, and ion homeostasis to mitigate chromium toxicity in wheat

Abstract

This research explored how exogenous application of allicin can assist wheat plants in coping with the stress caused by chromium (Cr). The findings indicate that Cr toxicity (30 mg kg^-1) conspicuously reduced biomass, chlorophyll content, and leaf relative water content (LRWC) in wheat plants. A significant surge in oxidative stress, as demonstrated by higher levels of hydrogen peroxide, superoxide radicals, and malondialdehyde alongside elevated lipoxygenase activity and electrolyte leakage percentage, was noticed in Cr-stressed plants. Chromium toxicity also induced higher methylglyoxal generation in plants. Allicin foliar administration (50, 100, and 200 µM) visibly curtailed Cr phytotoxicity and improved biomass. Allicin applied as 200 µM maximally subsided oxidative stress by augmenting the activities of superoxide dismutase (SOD), peroxidase (POD), catalase(CAT), and ascorbate peroxidase (APX), as well as the levels of ascorbate and reduced glutathione (GSH). Higher endogenous hydrogen sulfide (H₂S) and nitric oxide (NO) concentrations in allicin-treated plants further stimulated the antioxidant defense system of Cr-challenged plants. Allicin supplementation maintained GSH : GSSG ratio in Cr-stressed plants, suggesting a better redox balance. A noticeable accretion of soluble sugars, flavonoids, and phenolics due to allicin safeguarded plants from metal-induced damage and its associated oxidative stress. These findings highlight that exogenous application of allicin can be used as a promising strategy to alleviate Cr toxicity in wheat plants. Future studies should assess the effectiveness of exogenous allicin application in other cereal crops under controlled and field conditions. Additionally, exploring the molecular mechanisms underlying metal stress tolerance in allicin-treated plants will deepen our understanding.