Abstract:

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, plays 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 accumulation was also earlier than other tested cultivars. The characters of the genotype Ⅲ with medium strength fiber (NuCOTN 33B) were intermediate. From above results, we suggest that the differences of the dynamics of soluble sugar and β-1,3-glucan contents and sucrose synthetase and β-1,3-glucanase might be one of the physiological reasons for the differences in the cellulose accumulation and fiber strength formation. Further, the occurrence of β-1,3-glucan content peak may be proposed as a sign of the onset of secondary wall thickening in the fiber cell.

Key words: Cotton, Genotype, Cotton fiber thickening development, Physiological characters, Fiber strength