中文摘要：

选择3类棉纤维比强度差异明显的品种，于2004-2005年在江苏南京（长江流域下游棉区）研究棉纤维加厚发育过程中主要生理特性的基因型差异及对纤维比强度的影响，为探索改善棉纤维比强度的生理调控途径提供理论依据。结果表明，高纤维比强度基因型（科棉1号）棉纤维中可溶性糖转化多，进入纤维次生壁加厚发育期的β-1，3-葡聚糖含量峰值高，纤维素合成关键酶（蔗糖合成酶和β-1，3-葡聚糖酶）活性增强快、峰值高，纤维素累积速率平缓且快速累积期长；而较低纤维比强度基因型（苏棉15和德夏棉1号）的棉纤维加厚发育生理特征与此相反；中等棉纤维比强度基因型（美棉33B）则介于上述两者之间。与纤维素生物合成相关的物质和关键酶活性变化的基因型差异是造成纤维素累积速率及纤维比强度差异的主要生理原因之一。此外，β-1，3-葡聚糖含量的剧增可作为棉纤维进入次生壁加厚发育阶段的一个重要特征。

英文摘要：

The secondary wall thickening stage is a key period to cotton fiber strength development and many complex physiological and biochemical processes are involved in it. To investigate the relationship between the genotypic differences in some physiological characteristics during cotton fiber thickening and the fiber strength, we carried out the 2-year experiments in Nanjing, Jiangsu Province （cotton belts in lower basin of the Yangtze River） in 2004-2005 by using three genotypes with significant difference in fiber strength as materials. Flowers were labeled at anthesis and sampling was conducted every seven days from 10 DPA （day post-anthesis） on. The results showed that the genotype Ⅰ with high strength fiber （Kemian 1 was representative cultivar） had more soluble sugar transformed, higher peak of β-1,3-glucan content at the onset of fiber secondary wall thickening. Sucrose synthetase and β-1,3-glucanase, playing very important roles in fiber development, always kept in higher activities in Kemian 1 than in other tested cultivars during the fiber secondary wall thickening. All these resulted in longer term and more tempered cellulose accumulation and higher strength fiber formation. On the contrary, the genotype Ⅱ with lower strength fiber （Dexiamian 1 and Sumian 15 were representative cultivars） had less soluble sugar transformed, lower peak of β-1,3-glucan content at the onset of fiber secondary wall thickening, slower increasing trend of the key enzymes activities and a more quickly descended trend afterward, leading to a shorter term and rapid cellulose accumulation and lower strength fiber. Dexiamian 1, an early cultivar, reached the peak values of β-1,3-glucan content and key enzymes activities earlier than other cultivars for about a week. And the starting time of cellulose rapid accmnulation was also earlier than other tested cultivars. The characters of the genotype Ⅲ with medimnstrength fiber （NuCOTN 33B） were intermediate. From above results, we suggest that the differences