Abstract: Cadmium is a non-essential element for plant growth which has serious biological toxicity and comparing with other heavy metals, Cadmium is more prone to accumulate in plants . The present study was conducted in nutrient solution to investigate the effects of exogenous nitric oxide (NO) on growth of cucumber seedlings , photosynthetic characteristics
and active oxygen metabolism in cucumber leaves under consistently different concentration of Cadmium stress (100 μmol L^{- 1} , 300μmol L ^{- 1} , 500μmol L^{- 1} ) . The results showed that 300μmol L ^{- 1} exogenous sodium nitrop russide (SNP) , a nitric oxide donor , could significantly alleviate the injury to cucumber under Cadmium stress . The treatment of SNP showed
the best results when cucumber under 300μmol L^{- 1} Cd^{2 +} stress , which increased the seedling growth , the activity of SOD, POD, and the content of photosynthetic pigment and proline . Moreover , exogenous nitric oxide markedly decreased the content of MDA under 300μmol L^{- 1} Cd²⁺ stress .

Key words: Cd²⁺ stress