Nitric oxide (NO) involves in plant response to various stresses.In the present study,maize seedlings were treated with cadmium alone or in combination with sodium nitroprusside (SNP,a NO donor),SNP plus 2(4carboxy2phenyl)4,4,5,5 tetramethylimidazoline1oxyl3oxide (cPTIO,a NO scavenger) or K₃Fe(CN)₆ (an analog of SNP).After 24 h,some parameters correlating with stresses were investigated to analyze the effect of NO on cadmium tolerance.We found that supplementation of Cd with SNP exhibited significantly greater root elongation and lower Cd accumulation in root tips as compared with Cd treatment alone.Meanwhile,Cdinduced oxidative damage including electrolyte leakage,superoxide radical (O^-·₂) and hydrogen peroxide (H₂O₂) was alleviated by SNP supply.In addition,Cdtriggered increases in superoxide dismutase (SOD),catalase (CAT) and ascorbate peroxidase (APX) activities were also decreased by SNP addition.Although Cd stress had no effect on glutathione reductase (GR) activity,supplementing with SNP increased GR activity as compared with Cd treatment alone.The ameliorating effects of NO were specific,because K₃Fe(CN)₆ which did not release NO,did not show the effects of SNP.The effects of SNP were reversed by simultaneous application of cPTIO.All together,these results suggested that NO ameliorates Cd toxicity by decreasing endogenous Cd accumulation and Cdinduced oxidative damage.