| The present study was conducted under controlled hydroponics to value systematically the responses of morphology and material accumulation of different cotton varieties "Jimian20" "Zhongmiansuo29" and "ZhongmiansuoSO" in Enhanced Ammonium Nutrition (EAN) and the effects of different NH//NCV percentage nitrogen nutrition on the morphological and physiological changes of the same variety of cotton (Jimian20). At the same time, a field experiment was carried out to study the effects of Enhanced EAN under natural environments. The results were as followed as:EAN promoted growth of all the three cotton varieties. Compared with single nitrate nutrition, EAN significantly increased cotton' s leaf area, taproot length, primary lateral root number, dry weights of whole plant and petiole respectively, but lightly affected the height of stem and the rate of leaf emergence.Compared with single nitrogen nutrition, cotton had the maximum of plant growth. root activity, net photosynthetic rate, and chlorophyll content and nitrogen accumulation in functional leaves when NH4+/NO3~ ratio in solution was 25/75. However, when NH4+/NO3" ratio in solution was 25/75-50/50, cotton plants could grow regularly.Nitrogen nutrition significantly affected carbohydrate metabolism in various organs of cotton. The relative content of soluble sugar in various organs and the accumulation of soluble sugar in whole cotton plant were maximal in Enhanced Ammonium Nutrition condition, and minimal in single ammonium nutrition. However, the relative content of starch of the treatments over 25/75 (NH4+/NC>3~) ratio was less than in single nitrate nutrition solution. The starch accumulation of cotton plant was maximal in solution of25/75 (NH4+/NO3~) ratio and minimal in solution of 100/0 (NH4VNO3") ratio.Compared with single nitrate nutrition, the solution of 25/75-100/0 NH/TNCV ratio significantly increased soluble protein accumulation in leaves and roots of cotton. When NH4VNO3~ ratio in solution was 50/50, soluble protein accumulation in leaves was maximal. And when NH4VNO3~ ratio in solution was 75/25, soluble protein accumulation in roots was maximal.With the increase of NH/ density and the decline of NO3~ density, the nitrate content in the petiole and NR activity in functional blade declined. But ammoniac nitrogen content increased in every organ of cotton with the increase of NH4~ density, and the maximum of ammoniac nitrogen accumulation in each cotton presented in the solution of 75/25 (NlV/NCV) ratio, not in the solution of 100/0 (NH4"/NO3~) ratio.The field experiment showed that with the increase of nitrogen fertilizer, remained nitrogen and ammonium nitrogen in cotton field increased and the difference between DCD and no-DCD became distinct. At the same level of nitrogen, remained nitrogen in soil was less and the remained ammonium nitrogen in soil was more with DCD treatment than in soil with the no-DCD treatment. Urea fertilizer in soil mixed with 2% DCD significantly affected the physiological metabolism of cotton. It increased the content of chlorophyll, soluble protein, ammoniac nitrogen and soluble sugar in functional leaves, but declined the content of starch and nitrate nitrogen in functional leaves during the whole growth period of cotton. But the magnitude of effect between different treatments varied in different development stages. EAN also increased the dry matter accumulation, but not starch and nitrate nitrogen in the buds of cotton formed in different periods.With the increase of nitrogen fertilizer applied in field, the content of chlorophyll, soluble protein, ammoniac nitrogen and nitrate nitrogen in functional leaves increased, but the content of soluble sugar and starch declined.
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