| Cotton (Gossypium hirsutum L.) is not only one of most important fiber crops but also one of important oil crops in the world, and plays an important role in our national economy. Cotton fiber was developed from the outer epidermis of cottonseed, and its development, to a great extent, is synchronized with the growth of cottonseed. So, it could be supposed that the nutrients in cottonseed kernel may affect the development of fiber while the nutrients of cottonseed kernel accumulated.Auxin (IAA) plays an important role in regulating the cotton boll and fiber development. Previous studies have shown that IAA can promote the differentiation of ovule epidermal cells, increase the number of fibers, and improve the fiber production. However, the physiological mechanism promoting fiber development of IAA is still not clear. Most of researchers only focused on the influence of the IAA level on fiber development and pay less attention on the impact of IAA on cottonseed development and nutrients accumulation in cottonseed kernel. So, we think it is necessary to study the effects on cottonseed kernel nutrients while studying the mechanism of the IAA on fiber differentiation development because fiber is one part of the cottonseed.In this study, cotton varieties such as Texas Marker-1(TM-1), IF-11, Jimian14(J-14) and IF-11(no) were used as materials. The epidermis of ovule after cultured in vitro with different hormones were observed by electron microscope scanning (EMS), the endogenous IAA content, nutrition quality of cottonseed kernel and fiber quality of these varieties were measured, the relationships between IAA content and cottonseed kernel nutrient and fiber qualities were analyzed while the effects of exogenous IAA application on cottonseed kernel nutrients content and lint percentage were studied. The main results were as follows:1. By EMS of epidermal of unfertilized ovules (-1DAP) after cultured3d in vitro with different hormones, it was found that IAA could induce the differentiation of ovule epidermal cells and GA3couldn’t obviously but could strengthen the inducement role of IAA.2. The elongation of fiber on the ovule (2DAP) of varieties IF-11and J-14need different hormones under in vitro culture. It was observed that the elongation of fiber was took place on the surface of ovule of IF-11and no long fiber was found of J-14under added GA3alone in medium. It was concluded that the IAA is necessary for fiber development in early stage of fiber development and the high IAA level in ovule helps cotton fiber development.3. After5d of flowering, there were significant differences of endogenous IAA content in ovule of four varieties. The endogenous IAA content of IF-11was obviously higher than TM-1. The cottonseed kernel protein content of IF-11is significantly higher than other three varieties, and crude fat content and gossypol content of IF-11were far less than TM-1, J-14and IF-11(no). There was a positive correlation between the IAA content and cottonseed kernel protein content, and negative with the crude fat content and gossypol content, while all the correlations were not significant difference.4. Compared with J-14and IF-11(no), the lint percentage of IF-11was increased and Micronaire index of fiber was decreased. There was a negative correlation between IAA content and fiber quality traits, and a positive with lint percentage. Cottonseed kernel protein content was also positively correlated with lint content, but the crude fat content and gossypol content were negatively correlated with lint percentage significantly.5. The nutrition quality of cottonseed kernel was also affected by exogenous application of IAA. The protein content of cottonseed kernel was increased and the crude fat content reduced after application of endogenous IAA. It could be concluded that the formation of nutrition quality in cottonseed kernel could be regulated by use of growth regulators. |
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