Physiological and Biochemical Regulation Mechanism of Exogenous Hydrogen Peroxide in Alleviating NaCl Stress Toxicity in Tartary Buckwheat ( (L.) Gaertn).

We aimed to elucidate the physiological and biochemical mechanism by which exogenous hydrogen peroxide (HO) alleviates salt stress toxicity in Tartary buckwheat ( (L.) Gaertn). Tartary buckwheat "Chuanqiao-2" under 150 mmol·L salt (NaCl) stress was treated with 5 or 10 mmol·L HO, and seedling growth, physiology and biochemistry, and related gene expression were studied. Treatment with 5 mmol·L HO significantly increased plant height (PH), fresh and dry weights of shoots (SFWs/SDWs) and roots (RFWs/RDWs), leaf length (LL) and area (LA), and relative water content (LRWC); increased chlorophyll a (Chl a) and b (Chl b) contents; improved fluorescence parameters; enhanced antioxidant enzyme activity and content; and reduced malondialdehyde (MDA) content. Expressions of all stress-related and enzyme-related genes were up-regulated. The gene (flavonoid synthesis pathway) exhibited similar up-regulation under 10 mmol·L HO treatment. Correlation and principal component analyses showed that 5 mmol·L HO could significantly alleviate the toxic effect of salt stress on Tartary buckwheat. Our results show that exogenous 5 mmol·L HO can alleviate the inhibitory or toxic effects of 150 mmol·L NaCl stress on Tartary buckwheat by promoting growth, enhancing photosynthesis, improving enzymatic reactions, reducing membrane lipid peroxidation, and inducing the expression of related genes.