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Exogenous amino acids increase antioxidant enzyme activities and tolerance of rice seedlings to cadmium stress

Cadmium (Cd) contamination has posed a serious problem for safe food production and become a potential agricultural and global environmental problem. A hydroponic experiment was carried out in this study to characterize the modulation of exogenous amino acids (glutamate, glycine, and cysteine) for antioxidant defense system against Cd‐induced toxicity in rice (Oryza sativa L.) seedlings exposed to 5.0 μmol L−1 Cd. Cd stress (5.0 μmol L−1) caused a significant inhibition of the rice seedlings growth, and the three amino acids alleviated the damaging effects of oxidation in varying degrees. Glutamate and glycine at three application rates did not influence rice plant biomass in comparison to the only Cd treatment, but 25 μmol L−1 cysteine treatment reached the control treatment level. For 25 and 100 μmol L−1 cysteine treatment, the Cd uptake in the whole rice plant was significantly higher than those in the only Cd treatment. Though all of the three amino acids played a role in decreasing lipid peroxidation, increasing catalase, superoxide dismutase activities, and reduced glutathione contents, the effect of cysteine treatment was relatively better. The main reason may be ascribed to that cysteine represents the most important conceptual fragments of glutathione, which is the main precursor of the phytochelatins. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 155–161, 2017