Abstract:Nitrogen (N) is an essential element for plant growth and development, and lack of boron (B) will affect N metabolism in the body, forcing plants to obtain N sources from other ways. Non-toxic dose of cyanide (CN-) can provide auxiliary N source for plants through β-cyanoalanine synthetase (β-CAS) degradation pathway. Cysteine (Cys) is considered to be a limiting factor in the β-CAS pathway. In this study, rice (Oryza sativa) seedlings were treated with CN--B-Cys, CN-+B-Cys, CN--B+Cys and CN-+B+Cys to evaluate the combined regulatory effects of B and Cys on the absorption and assimilation of CN- in rice seedlings. The results showed that CN- absorption rate of rice seedlings treated with CN--B+Cys was the highest (P<0.05), followed by CN-+B+Cys. The residual concentration of CN- in rice seedlings treated with CN--B+Cys and CN-+B+Cys was significantly lower than that of other treatments (P<0.05). CN--B+Cys processing of rice seedlings have the highest CN- assimilation rate (P<0.05), followed by CN-+B+Cys, CN--B-Cys and CN-+B-Cys. Meanwhile, the NH4+ absorption rate and assimilation rate of rice seedlings treated with CN--B+Cys were the highest (P<0.05), followed by CN-+B+Cys. Therefore, the addition of Cys and B deficiency treatment could promote the absorption and assimilation rate of CN- and NH4+ in rice seedlings, and reduce the toxic damage of CN- to rice seedlings.