Observation Of Cotton Fiber Elongation And Analysis Of The Content Change Of Phenylpropanoid Compounds In Developing Fiber Of Sea Island Cotton And Upland Cotton

Cotton fiber is the main raw material of textile industry. Fiber quality directly affects the quality of textiles. Because of the outstanding characteristics of Sea Island Cotton (Gossypium barbadense L.) fiber, which is long, thin and strong, it has become the best quality varieties of cultivated cotton. But its relatively low yield becomes the primary defect. And the advantage of the Upland Cotton (Gossypium hirsutum L.) is high yield. The differentiation of cotton fiber and development process is also the formation of yield and quality. A further understanding of Sea Island Cotton and Upland Cotton fiber developmental process and quality formation mechanism is of great significance to improve cotton fiber quality.The main structural materials of plant cell secondary wall thickening are cellulose and phenylpropanoid compounds. They are the major substances of the cell wall structure compositions. The phenylpropanoid compounds affect cell wall growth, strength, morphogenesis and stress resistance. Cotton fiber structure is a typical secondary wall structure, and understanding the phenylpropanoid compounds of cotton fibers is important to study the physical quality formation of cotton fiber quality formation.In the present study, Sea Island Cotton and Upland Cotton fiber in different developmental stages were used to measure the length of fiber from5DPA-25DPA (Day Post-Anthesis) by using water flushing method. The results showed that the Sea Island Cotton and Upland Cotton fiber length increased with the time increasing. The length of cotton fiber increased fast from5DPA-21DPA, while from23DPA, cotton fiber elongation rate gradually decreased. In25DPA, the sea island fibers of three varieties being tested were longer than the Upland Cotton fibers. The varying tendency of cotton fiber length with DPA displayed "S" curve. Through the analysis and comparison of different developmental stages of Sea Island Cotton and Upland Cotton fiber length and dynamic changes eigenvalue, the results showed that rapid elongation period lasting time of the Upland Cotton fiber was shorter than that of Sea Island Cotton; And the maximum fiber elongation rate of Upland Cotton fiber was lower than that of Sea Island Cotton fiber. There existed differences of the rapid elongation period duration, and the maximum fiber elongation rate between Sea Island Cotton fiber and Upland Cotton fiber. The differences may be one of the reasons why the Sea Island Cotton fiber length is different from Upland Cotton fiber length.This experiment used Klason method for the determination of acid insoluble lignin content of developing fiber of Sea Island Cotton and Upland Cotton. The results showed that acid insoluble lignin content of cotton fiber per boll increased with the increasing DPA. Sea Island Cotton fiber acid insoluble lignin content was lower than Upland Cotton fiber. Cotton fiber acid insoluble lignin content changed in agreement with Logistic Function, the rapid accumulation period of acid insoluble lignin content of Upland Cotton was longer than Sea Island Cotton. And the timepoint of maximum cumulative rate of Upland Cotton appeared later than that of Sea Island Cotton. Sea Island Cotton acid insoluble lignin content was significantly different from Upland Cotton in the same developmental period. Cotton fiber quality, especially the breaking strength showed significant negative correlation with acid insoluble lignin content.For further validation of phenylpropanoid compounds in cotton fiber development, experiments used TGA (Thioglycolic acid) method to determine the lignin content of Sea Island Cotton and Upland Cotton fiber in development, and AB (Acetyl bromide) method to determine the phenylpropanoid compound content of Sea Island Cotton and Upland Cotton fiber in development. The Results concluded unanimously with the sulfuric acid method.The above analysis results showed:phenylpropanoid compound content of cotton fiber may apply certain effect on the fiber quality formation. This experiment provides some reference for further understanding of the Sea Island Cotton fiber and Upland Cotton fiber elongation process and quality formation mechanism.