中文摘要：

在大田栽培条件下，研究了4个基因型棉铃对位叶花后碳氮比，可溶性蛋白含量及内源保护酶活性动态变化的基因型差异及其与铃重形成的关系。试验结果表明，棉铃对位叶花后N代谢活跃，内源保护酶活性高，叶片生理活性较强的基因型（如苏棉15和科棉1号），其铃重的快速增长期长，单铃棉纤维干重高，最终铃重较高；反之，棉铃对位叶生理活性弱、功能期短的基因型（如德夏棉1号），棉铃对位叶中C／N高，内源保护酶活性低或下降过快，造成铃重快速增长期缩短，单铃纤维干重降低，最终铃重较低；美棉33B棉铃对位叶中C／N和内源保护酶活性变化特征介于上述两种类型之间。由以上结果可以得出，在本试验条件下，棉铃对位叶生理特性的基因型差异是导致不同铃重形成的重要生理原因之一。

英文摘要：

To Study the genotypic differences of physiological characteristics in leaves subtending bolls and its relationship with the boll weight forming, field experiments were conducted in Nanjing, Jiangsu Province （cotton belts in lower basin of the Yangtze River） in 2004-2005 by using four cotton genotypes. The study focused on the time course of C/N ratio, soluble protein content and internal source protective enzyme activity in the leaves subtending bolls. Flowers were labeled at anthesis and leaves subtending boll were sampled every 7 days from 10 DPA （day post-anthesis） in 2004 and every 7 days from 5 DPA in 2005. The results of 2-year experiments showed that the leaves subtending bolls of SC-15 and KC-1 had more active nitrogen metabolism and higher soluble protein content after anthesis, and had higher physiological activities and longer duration of function, including higher activity of internal source protective enzymes, lower MDA content during the middle and later development stages of bolls. These phenomena led longer time for rapid increasing of boll weight, higher fiber weight in single boll and resulted in higher boll weight finally. On the contrary, the leaves subtending bolls of DSC-1 had shorter duration of function, and lower physiological activities including higher C/N ratio, sharp drop of internal source protective enzyme activities and higher extent of lipid peroxidation.These items caused the shorter time for rapid increasing of boll weights, lower speed for fiber weight increasing and resulted in lower boll weight finally. The items in AC-33B were between the above two types. From above results, we suggested that under our experiment condition, the genotypic difference of the physiological characteristic in leaves subtending bolls might be one of important reasons causing, the difference in boll weights forming.