Application of silicon improves rhizosheath formation, morpho-physiological and biochemical responses of wheat under drought stress

Background and aims: Rhizosheath, a mixture of soil and mucilage that remains attached to the root system after being removed from the soil and shaken, plays a prominent role in the resistance of plants to drought stress. This study aims to investigate the effect of silicon (Si) on rhizosheath formation and mitigate the effects of drought stress in wheat. It was hypothesized that Si positively enhances root hair formation and rhizosheath formation under soil drying conditions, improving plant access to water under soil drying conditions. Methods: Wheat seeds were grown under different levels of Si (control, 150 and 300 mg kg⁻¹ monosilicic acid, and 150 and 300 mg kg⁻¹ nano-silicon) and irrigation (0.4 field capacity (FC) and 0.8 FC) under greenhouse conditions. Results: Under drought stress, the application of Si significantly increased root hair length, density, rhizosheath formation, and transpiration rate. Applying Si increased the length of root hairs by 45–107% and their density by 25–78%. Under drought stress, application of 150 and 300 mg kg⁻¹ of monosilicic acid and nano-silicon increased rhizosheath formation by 40.3, 48.2, 16.8, and 17.5%, and transpiration rate by 17.8, 36.4, 11.4, and 29.1%, respectively. Si also increased superoxide dismutase and catalase activity, while decreasing malondialdehyde and hydrogen peroxide content. Conclusion: Silicon application in drought-stricken wheat improved water uptake, leading to improved plant water relations and other morpho-physiological and biochemical responses. This was achieved by modifying root system traits, particularly increasing root hair length and density, which facilitated the formation of rhizosheath.