Abstract: The study with water culture showed that nitrate stress had significant inhibitory effects on the plant growth, especially the shoot growth of cucumber seedlings. On the 7th day under nitrate stress, the shoot fresh mass per plant decreased by 12.77 g, leaf SOD, POD and CAT activities increased, while leaf APX, DHAR and GR activities decreased significantly, compared with the control. The addition of low concentration (0.05 mmol·L^-1) LaCl₃ increased the shoot fresh mass per plant by 35%, enhanced the leaf thermally stable protein content and SOD, POD, CAT, APX, DHAR and GR activities, and decreased the leaf MDA content and electrolytic leakage, resulting in a definite alleviation of the inhibitory effects of nitrate. However, an addition of high concentration (0.5 mmol·L^-1) LaCl₃ had no obvious alleviation effect. It was concluded that the addition of certain concentration LaCl₃ could alleviate the nitrate stress on cucumber via increasing anti-oxidative enzymes activities and thermally stable protein content.

Key words: Tarim Desert Highway shelter forest, soil microbe,  , soil microbial metabolic activities, microbial biomass, enzyme activity.