Foliar Application of Potassium Silicate Mitigates Terminal Heat Stress in Wheat through Enhanced Antioxidant Defense and Physiological Stability

Potassium Silicate Mitigates Terminal Heat Stress in Wheat

Abstract

Terminal heat stress during the reproductive phase severely impairs wheat (Triticum aestivum L.) productivity by inducing oxidative damage and disrupting physiological homeostasis. This study evaluated the role of foliar-applied potassium silicate in enhancing antioxidant defense and physiological resilience of wheat under varying sowing dates. A field experiment was conducted using a split plot block design with four sowing dates (25 October, 5 November, 15 November, and 25 November) and eight foliar treatments, including potassium silicate (2% and 3%) applied at booting and/or anthesis, potassium nitrate (2%), and an untreated control. Delayed sowing significantly intensified oxidative stress, as indicated by increased DPPH radical scavenging activity, superoxide dismutase (SOD), and catalase (CAT) activities, along with elevated lipid peroxidation and proline accumulation, while chlorophyll content declined. The application of 3% potassium silicate at both booting and anthesis markedly enhanced antioxidant capacity, recording the highest DPPH activity (22.70 units mg⁻¹ FW), SOD (457.6 mg⁻¹ FW), and CAT activity (695.43 H₂O₂ min⁻¹ g⁻¹ FW), and significantly reduced lipid peroxidation (0.727 nmol cm⁻¹ FW) compared with the control. Additionally, this treatment improved chlorophyll content (3.194 mg g⁻¹ FW) and proline accumulation (0.612 mg g⁻¹ FW), indicating enhanced membrane stability and osmotic adjustment. These findings demonstrate that silicon-mediated modulation of antioxidant and osmoprotective mechanisms effectively mitigates terminal heat-induced oxidative stress in wheat, highlighting foliar potassium silicate as a promising strategy for enhancing crop resilience under warming climatic conditions.