The Study On Development Of Fiber And Accumulation Of Pigment Precursor In Brown Cotton

The causes for poor quality may possibly be that the process of fiber development is accompanied by the accumulation of pigment, and the portion of synthetic materials is used to change into pigment, so that the cellulose deposition is not sufficient in brown cotton. In this article, using brown cotton bolls of different developmental stages as main materials, the effect of accumulation and distribution of photosynthetic products in fiber development and pigment formation, the fiber development-related enzymes activities, and the relationship between the accumulation of pigment precursor and fiber quality were investigated in order to explore the formation mechanism of fiber quality of brown cotton and the impact on fiber quality by pigment accumulation, reveal the causes for poor quality and provide theoretical basis for fiber quality improvement of brown cotton.The major results were as follows:(1) In comparison with white cotton, brown cotton has many poor traits, such as lower lint weight and lint percentage, shorter length of fiber, poor uniformity and breaking strength, higher short fiber index, meanwhile with the increase of pigment content, length of fiber, uniformity and breaking strength go to the bad, and short fiber index increase.(2) The accumulation regulation of dissoluble sugar in leaves, seed coats and fiber of different genotypes of cottons was basically as the same. By calculating the transport capacity of dissoluble sugar, the transport index of white cotton was 0.125, while the highest transport index in brown cottons was 0.119. The result of analysis of fiber elongation and cellulose accumulation showed that cellulose accumulation had the largest effect on fiber elongation, and the direct effect of dissoluble sugar content in fiber on fiber elongation was greater than that in seed coats and leaves.(3) In fiber development process, the fiber elongation rate of brown cotton was lower than of white cotton, and fiber elongation stopped earlier, around 30DPA, while the period of white cotton fiber elongation was longer and continued to 35DPA. The cellulose accumulation rate of brown cotton was lower than of white cotton. The rapid accumulation period was shorter and probably continued to 25DPA, while white cotton continued to 30DPA. The content of brown cotton cellulose was low and only about 85% of white cotton at 40DPA.(4) Comparing the fiber development-related enzymes activities, at the early period of fiber development (before 20DPA), SS activity in brown cotton was significantly lower than in white cotton, while POD and IAAO activities were higher. At the later period of fiber development (from 25DPA),β-1,3-glucanase and POD activities were lower than in white cotton. Regression analysis and comparison of the multiple regression correlation coefficient of enzymes indicated that SS andβ-1,3-glucanase activities had the positive effect on fiber elongation, while POD and IAAO activities inhibited fiber elongation development.(5) Analyzing the relationship between the content of condensed tannin, cellulose accumulation characteristics and glucose metabolism enzymes activities, the results suggested that the effect of SS activity on cellulose accumulation was greater than on synthesis of condensed tannins in different genotypes of cottons, increasing SS activity could significantly improve cellulose content, but obtain the negative effects on condensed tannin content. G6PDH activity and condensed tannin content of the regression coefficients in brown cotton was larger than in white cotton, and the rank order of different genotypes of brown cottons as follows: dark brown ANL-1> mid-brown ANL-1> light brown ANL-2, which indicated that G6PDH activity catalyzed the synthesis of condensed tannins, and lay the foundation for formation of pigment.(6) Comparing the synthesis of condensed tannin and fiber elongation in brown cotton, it was found that during 5-15DPA, it was the period when the fiber was elongated rapidly, the content of condensed tannin of brown cotton was significantly higher than of white cotton, meanwhile, the rapid synthesis of cellulose and condensed tannins coincided, of which the formation of fiber quality based on the deposition of cellulose was weakened due to the synthesis of condensed tannins, that may be the cause for poor quality of brown fiber, such as lint length and breaking strength, compared with white cotton.