Effects of Nitrogen Forms on the Activities of Key Enzymes for NH_4~+ Assimilation at Seedling Stage of Different Wheat Cultivars with Special-End Use

With nutrient solution culture method,the activities of key enzymes for ammonia assimilation(glutamine synthetase and Glu synthetase) in wheat leaves at one and a half leaves stage were carried out with strong-gluten wheat cultivars of Yumai 34,Zhengmai 9023 and Zhengnong 16,and medium-gluten wheat cultivar of Yumai 49,and weak-gluten wheat cultivar of Yumai 50;the effects of nitrogen forms,NO3-,NH4+ and urea on the enzyme activities were studied in the fourth leaf full expended stage.The result showed that at one and a half leaves stage,the total GS activities showed as: weak-gluten wheat cultivarmedium-gluten wheat cultivar strong-gluten wheat cultivars.The activities of GS1 were higher than that of GS2,and the differences of the activities of GS1 among different cultivars were very little whereas that of GS2 were very large as strong-gluten wheat cultivarsmedium-gluten wheat cultivarweak-gluten wheat cultivar.The activities of GOGAT of weak and middle gluten wheat cultivars were slightly higher than that of strong-gluten wheat cultivars.At the fourth leaf full expended stage,as to strong and weak gluten wheat cultivars,the GS activities of NO3-treatments were the highest;as to medium-gluten wheat cultivar,the GS activities of urea treatment were the highest.At the same time,the GS1 activities decrease in all treatment.Cultivars and N forms had no effect on GS1 but more effect on GS2.NH4+ could increased the GS2 activity of medium and weak gluten wheat cultivars while decreased that of strong-gluten wheat cultivars;urea could increased the GS2 activity of medium-gluten wheat cultivars,maintained that of Yumai34 in constant level,while decreased that of weak-gluten wheat cultivar and other strong-gluten wheat cultivars;NO3-increased the GS2 activity of weak-gluten wheat cultivar while decreased that of strong and medium-gluten wheat cultivars.The results showed that weak-gluten wheat cultivar was more sensitive to N form while strong-gluten wheat cultivars were more insensitive to N form,and medium-gluten wheat cultivar was in the medium.