Physiological Characteristics of Boll-Leaf System and Boll Weight Space Distributing of Cotton Under Different Nitrogen Levels

【Objective】The experiment was conducted in order to study the rules of Nitrogen on the cotton source and sink system. 【Method】Using Bt-transgenic hybrid cotton variety CCRI29 as material, we studied the effects by applying different level of nitrogen fertilizer (225.0 kg·ha-1, high; 112.5 kg·ha-1, medium; 0 kg·ha-1, low) in the field in the years of 2002-2003. The plant density employed was about 53 336 per hectare. 【Result】(1) Compared to mid-nitrogen and low-nitrogen, high-nitrogen promoted chlorophyll accumulating in leaf growth anaphase on fruit branch, which extended the leaf function period. The dissoluble protein content of leaf was the lowest under the treatment of low-nitrogen, and the chlorophyll content decreased rapidly in leaf growth anaphase, which accelerated the leaf’s senescence. (2) Different nitrogen levels affected the carbohydrate metabolism in various organs of cotton plants. The carbohydrate synthesis was inhibited under high-nitrogen levels, but low-nitrogen level promoted carbohydrate accumulation in leaf on reproductive branch. Different nitrogen levels had no significant effect on carbohydrate concentration in seed cotton. (3) Nitrogen can enhance activity of SOD and POD to some extent. The order of their activity of leaf on the lower branch was mid-nitrogenhigh-nitrogenlow-nitrogen, but the order of leaf activity on the middle branch was high-nitrogenmid-nitrogen low-nitrogen. 【Conclusion】Changed nitrogen application amount had some effects on cotton growth and development. The premature senescence in cotton would be improved under middle nitrogen condition.