中文摘要：

选用3类棉纤维比强度差异明显的4个棉花品种,研究棉花伏前桃、伏桃、早秋桃和晚秋桃纤维加厚发育过程中主要生理特征的差异及与纤维比强度的关系。结果表明,棉花季节桃纤维加厚发育过程中物质转化特征和相关酶活性存在较大差异,最终导致纤维比强度差异的形成,且季节桃间的差异在各类品种内表现一致。伏前桃和伏桃纤维加厚发育处于较为适宜的温度条件（铃龄10-50d日均温26.0-28.5℃）和棉株生理年龄（3-9果枝）下,纤维素合成相关酶活性越高,相关物质转化越多,纤维素快增持续期长,纤维素累积速率平缓,越利于高强纤维的形成。早秋桃纤维发育后期温度条件较伏前桃差且棉株开始衰老,但其纤维合成相关物质转化率高,纤维素累积特征优于伏前桃,最终纤维强度高于伏前桃;随着铃龄10-50d日均温降至20℃以下和棉株进一步的衰老（16果枝以上）,晚秋桃纤维素快速累积期延长,相关物质转化率降低,纤维累积速率过慢,纤维细胞发育迟缓,造成最终纤维比强度较低。

英文摘要：

Fiber strength is one of the most important quality indexes of cotton （Gossypium） fiber and contributes highly to the yam strength. Normally, fiber strength is determined by fiber＇s secondary wall thickening stage in which many complex physiological and biochemical processes are involved. To investigate the physiological characteristic of cotton fiber thickening in seasonal bolls and its relationship with fiber strength, the experiments were carried out in Nanjing, Jiangsu Province in 2004-2005 by choosing four cultivars with significant difference in fiber strength as materials. Boll samples were labeled on anthesis day （July 15, July 25, Aug. 25, and Sept. 10） and expressed as PSB （pre-summer boll）, SB （summer boll）, EAB （early autumn boll） and LAB （late autumn boll）, respectively. The results of two-year experiments showed that there were great differences in matter transformation and related enzyme activities during cotton fiber thickening in seasonal bolls, and which resulted in different fiber strengths. The diversity of physiological indexes between bolls with different anthesis dates was similar in every cultivar （geno- type）. Under suitable temperature condition （mean daily temperature 26.0--28.5℃ during boll age from 10 to 50 days） and plant physiological age （about the third-ninth fruit branch）, the cotton seasonal bolls （PSB and SB）, which had more soluble sugar and sucrose transformed, higher [3-1,3-glucan content at the onset of the secondary wall thickening, and higher activities of sucrose synthetase and [3-1,3-glucanase, would get longer and tempered cellulose accumulation and higher strength fiber. EAB had worse temperature environment for fiber development than PSB during the later period, but it had higher matter transformation rate and better characteristic of cellulose deposition than PSB. As the result, fiber strength of EAB was higher than that of PSB. With the worse temperature condition （mean daily temperature lower than 20℃ during boll age