Effect of Combined Application Nitrate Nitrogen and Ammonium Nitrogen on Photosynthesis and Carbohydrate Metabolism of Flue-cured Tobacco

The experiment has studied the influence of different nitrogen forms [nitrate-nitrogen(NO-3N)/ammonium-nitrogen(NH-4N)] and proportions on photosynthetic and carbohydrate metabolism of flue-cured tobacco.The results show that the photosynthetic rate was enhanced as the nitrate-nitrogen application quantity increased under the same total nitrogen application level.60d days after transplanting ,the total chlorophyll of all treatments reached at the highest level,among them the treatment 3 was the highest.The content variation of starch had two evident peaks when the proportion of NO-3N reached at 75% in the field.