Investigation of the effects of exogenously applied L-cysteine on buckwheat (fagopyrum esculentum) under boron toxicity conditions

Boron (B) toxicity is a significant abiotic stress factor that disrupts cell structure and limits plant growth and development. This study investigated how exogenous L-cysteine application mitigates the adverse effects of boron toxicity on buckwheat (Fagopyrum esculentum Moench). Seedlings were treated with 100 µM L-cysteine for 2 days, followed by the application of 40 ppm boric acid for 5 days to induce boron stress. The boron toxicity treatment led to a decrease in root and stem lengths, as well as chlorophyll a, b, and total chlorophyll content. L-cysteine administration mitigated these effects by reducing lipid peroxidation (MDA) and hydrogen peroxide (H₂O₂) levels. Additionally, proline, total sugar, and total phenolic content increased, while antioxidant enzyme activities (superoxide dismutase, catalase, and ascorbate peroxidase) rose. Histochemical staining also showed a decrease in reactive oxygen species accumulation. At the molecular level, the expression of LHCb and AAO genes varied depending on the treatment. In conclusion, L-cysteine effectively reduces stress caused by boron toxicity in buckwheat, impacting physiological, biochemical, and molecular levels.