中文摘要：

以产量差异显著的14个棉花品种为材料,研究棉铃对位叶C/N的变化特征及其与棉铃干物质积累与分配的关系。结果表明,棉铃对位叶C/N随铃龄的变化可用y=at^2＋bt＋c拟合[y为C/N,t为铃龄（d）,a、b、c为常数],其主要特征值（a、b、c和C/N最大值）与单铃干物重（即单个棉铃的铃壳、棉籽和纤维3部分干重之和）和铃重（即棉籽和纤维两部分干重之和）存在极显著相关关系,而与衣分和铃壳率无显著相关关系。以a、b、c和C/N最大值为变量可将14个棉花品种聚类为Ⅰ（美棉33B等6个品种）、Ⅱ（科棉1号等6个品种）和Ⅲ（中棉所35和中棉所38）3个类群,三者棉铃对位叶C/N及单铃干物重的变化特征差异显著,其中类群Ⅲ铃龄10～17d期间的棉铃对位叶C/N显著高于类群Ⅰ和类群Ⅱ,铃龄24d之后仍保持在2.5左右,整个铃期内变幅最大,平均值最高,其单铃干物重快速增长期最长,平均增长速率最小,最终单铃干物重和铃重均最大,但3个类群棉花棉铃干物质在棉铃各部分分配率的动态变化无明显差异,最终衣分和皮棉产量与棉铃对位叶C/N变化特性无明显相关性。棉铃对位叶C/N变化的基因型差异显著,棉铃对位叶C/N在铃龄10～17d期间高、铃龄24d之后仍维持在相对较高的水平,有利于棉铃干物质的积累。

英文摘要：

To study changes of the C/N ratio in the subtending leaf of cotton boll and its relationship with boll dry matter accumulation and distribution, 14 cotton cultivars with significant differences in yield were chosen as materials. The results showed that dynamic changes of the C/N ratio in the subtending leaf of cotton boll could be simulated with quadratic： y=at^2＋bt＋c [y stands for the C/N ratio and t stands for boll age （d）]. Correlation analysis indicated that a, b, c and the maximum C/N ratio were significantly correlated with dry weight per boll （the total of boll shell, seed and fiber dry matter weight per boll） and boll weight （the total of seed and fiber dry matter weight per boll）, but not with lint percentage and boll shell percentage. Therefore, a, b, c and the maximum C/N ratio were selected as the variables for clustering analysis. The 14 cotton cultivars were clustered into 3 groups- Group Ⅰ （including American Cotton-33B etc.）, GroupⅡ （including Ke Cotton 1 etc.） and Group Ⅲ （including China Cotton Research Institute 35 and China Cotton Research Institute 38）. There were significant differences in dynamic changes of the C/N ratio and dry weight per boll among three groups. The C/N ratio of the Group Ⅲ was much higher than that of Group Ⅰ ＆ Ⅱ during the period from 10 to 17 days of boll age and still maintained around 2.5 after 24 days of boll age, showing a widest changing range and a highest average value during the whole boll developing stage. The boll dry matter accumulation of Group Ⅲ had the longest speedy rising period with the lowest velocity, which resulted in the highest final dry weight per boll and boll weight. However, there existed no significant difference in dry matter distribution in each part of cotton boll among three groups and no visible connection between the final lint percentage as well as lint yield and the characters of the C/N ratio in the subtending leaf of cotton boll. In conclusion, dynamic characters of the C/N ratio in the