Potassium-mediated Alleviation of Boron Toxicity in Sensitive and Tolerant Wheat (Triticum aestivum L.) Cultivars: Oxidative Stress, Antioxidant Response and Mineral Element Composition

Boron toxicity limits wheat productivity in boron-rich soils, yet the potential of potassium to alleviate boron-induced oxidative damage in cultivars with differing sensitivity remains poorly understood. This study investigated potassium-mediated mitigation of boron stress in two wheat (Triticum aestivum L.) cultivars, Bezostaya (sensitive) and Kutluk (tolerant). Germinated seeds were grown hydroponically under five treatment conditions (control, 5 mM B, 10 mM B, 5 mM B + 10 mM K and 10 mM B + 10 mM K). Growth parameters, chlorophyll content, oxidative stress markers (hydrogen peroxide [H₂O₂], malondialdehyde [MDA], proline), antioxidant enzyme activities (superoxide dismutase [SOD], catalase [CAT], ascorbate peroxidase [APX], guaiacol peroxidase [GPX], lipoxygenase [LOX]), and tissue mineral element concentrations (K, Cu, Na, Ca, Mg, Mn, Fe, Zn, B) were measured in shoot and root tissues. Boron exposure reduced growth and chlorophyll while increasing oxidative stress markers and enzyme activities. Tissue boron accumulated dose-dependently, whereas K, Ca, Mg, Na, Fe, Zn, Cu, and Mn concentrations declined significantly in most tissue-treatment combinations, indicating broad mineral nutrient disruption. Potassium supplementation partially reversed these effects by improving growth, reducing oxidative damage, restoring mineral element levels closer to control values and lowering boron accumulation. Enzyme activities remained elevated but below boron-only levels, suggesting reduced oxidative burden. The mitigation effect was more pronounced in the sensitive cultivar Bezostaya. These results indicate that potassium can reduce boron toxicity through modulation of antioxidant defense mechanisms and restoration of mineral nutrient balance, particularly in sensitive genotypes.