Exogenous Kinetin Mitigates Arsenic-Induced Oxidative Stress by Regulating ROS Homeostasis and Antioxidant Defense in Ocimum Basilicum L.

Integrated physiological, biochemical, histochemical, and structural analyses demonstrated that exogenous kinetin effectively alleviates arsenic-induced oxidative damage in Ocimum basilicum. Arsenic (As) contamination poses a severe threat to crop productivity by inducing oxidative stress through excessive reactive oxygen species (ROS) accumulation. This study aimed to investigate the protective role of exogenous kinetin (KN), a synthetic cytokinin, in alleviating As-induced phytotoxicity in Ocimum basilicum L. through a comprehensive morphological, physiological, biochemical, histochemical, and structural approach. Plants were exposed to 5 and 10 mg kg−1 As stress concentrations, with or without exogenous 5 µM KN supplementation. Key parameters assessed included growth and biomass, photosynthetic parameters, ROS accumulation, lipid peroxidation, antioxidant enzyme activities, non-enzymatic antioxidants, and leaf microstructure. As stress significantly inhibited plant growth, reduced soil plant analysis development (SPAD) chlorophyll values, and caused oxidative damage, as indicated by elevated levels of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide radicals (O2•⁻). The activities of enzymatic and non-enzymatic antioxidant enzymes were considerably enhanced under As exposure. Microscopic analysis of roots revealed enhanced ROS accumulation along with compromised leaf epidermal integrity under As stress. Exogenous KN application reversed these effects by restoring growth parameters, enhancing photosynthetic and chlorophyll fluorescence parameters, reinforcing membrane integrity, and significantly upregulating both enzymatic and non-enzymatic antioxidant defense systems. KN further promoted proline accumulation and preserved the structural integrity of root and leaf tissues disrupted by As toxicity. These findings collectively establish that exogenous KN effectively confers As stress tolerance in O. basilicum through coordinated ROS homeostasis, enhanced antioxidant defense, and structural preservation. This study highlights KN as a promising and cost-effective phyto-protectant strategy for sustaining the productivity, biochemical performance, and medicinal quality of O. basilicum cultivated in As-contaminated soils, with broader implications for safe herb production and sustainable agriculture.