Study on Relationship between Nitric Oxide and Nitrate Reduction in Leaf of Alnus cremastogyne Effects of Exogenous Spd on NO3--N,NH4+-N Contents and Nitrate Reductase Activity of Salt Stressed Leaves and Roots of Cucumber Seedlings Damage Repair Effects of He-Ne Laser on Wheat Seedlings Exposed to Enhanced Ultraviolet-Birradiation RACE cloning and bioinformatics analysis of nitrate reductase in Beta vulgaris