Abstract: In order to study the effects of different concentration nitrate on root growth of wheat（Triticum aestivum L.） seedlings,the nitrate-free Hoagland solution was used as a control and Qiule 2122 was as test material. O₂^-·,H₂O₂,glutathione（GSH） contents and oxidoreductase activity in roots were detected by pectrophotometry and histochemical staining. The results showed that nitrate significantly increased superoxied anion（O₂^-·） but not peroxide hydrogen（H₂O₂）,and content of O₂^-· in seedlings with high nitrate （60 mmol/L） was higher than that in wheat seedlings with low nitrate （10 mmol/L）. Superoxidase（SOD） activity and GSH content were significantly decreased by low nitrate. On the contrary,low nitrate increased POD,GR,and GSH-PX activities to maintaining higher antioxidant capacity. Thus,low nitrate activated the growth of the roots of wheat seedlings. High nitrate inhibited the root growth due to the decreasing activities of SOD and GSH-PX,although high nitrate increased activities of GR and POD. Therefore,nitrate regulated growth of roots by means of changing O₂^-· content.

Key words: nitrate, reactive oxygen, wheat（Triticum aestivum L.）, GSH, roots