Redox homeostasis under summer stress: targeted ROS modulation by foliar kaolin-silicon mixtures in

Introduction: Climate change-driven increases in heat and drought intensity pose major challenges to grapevine performance, largely through the exacerbation of oxidative stress. This study investigated the effects of combined foliar applications of kaolin (Kl) and silicon (Si) on oxidative stress regulation in Methods: Grapevines were treated with different Kl + Si formulations (MiKS), consisting of 2% Kl combined with 2-8% Si, and evaluated at veraison (E-L35) and harvest (E-L38). Leaf proline content, total and specific reactive oxygen species (ROS, H Results: MiKS formulations significantly modulated grapevine redox metabolism, although responses depended on season, phenological stage, and Si concentration. Intermediate formulations, particularly MiKS 2 (2% Kl + 4% Si) and MiKS 3 (2% Kl + 6% Si), consistently reduced total ROS accumulation by up to 61.7% and decreased H2O2 levels under summer stress conditions. These responses were associated with transient increases in proline accumulation at veraison, enhanced CAT activity, and strong upregulation of Conclusions: The combined application of kaolin and silicon, especially at intermediate Si concentrations, promoted a more balanced redox state and improved oxidative stress management under Mediterranean summer conditions. These findings provide mechanistic evidence supporting MiKS formulations as sustainable, low-impact, climate-adaptive tools to enhance grapevine resilience under increasingly hot and dry viticultural scenarios.