Abstract:

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=at²+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: GroupⅠ(including American Cotton-33B etc.), GroupⅡ(including Ke Cotton 1 etc.) and GroupⅢ(including China Cotton Re-search 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 GroupⅢwas much higher than that of GroupⅠ&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 GroupⅢ 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 subtending leaf of cotton boll are significantly different among different genotypes, and the C/N ratio declined dramatically from 10 to 17 days of boll age and maintained at a relative higher level after 24 days of boll age, and that is favorable to cotton boll dry matter accumulation.

Key words:

Cotton boll, the subtending leaf of cotton boll, C/N ratio, Dry matter accumulation and distribution