Ultra-structural Observation On Fiber Cell And Lignin Content Analysis Of Secondary Wall During Cotton Fiber Development

Cotton is the main material for the textile industry.These single-celled hairs initiate at anthesis from the olvule epidermis.Differentiation and development of cotton fiber is the process of yield and quality formation.Chemical components and contents of fiber cell wall is directly related to productivity, quality and utilization of the cotton fiber.In order to understand the molecular and biological basis of the quality of cotton fiber correctly, it is very important to study the development of cotton fiber and changes of fiber cell wall components.The aim of this research is to to explore the form basis of cotton fiber quality and understand the general characters through the direction of cotton fiber development and lignin which forms cell wall cross-linking.At first, the ultra-structural developmental process of fiber cell from cotton (cv.Xinluzao 36) was observed by using transmission electron microscopy.At 10 DPA, the primary cell wall of cotton fiber was thin and even thickness, a big vacuole was located in the central of fiber cell, and there were mitochondria, ribosomes and Golgi bodies in the cytoplasm.At 20 DPA, a thin layer of the secondary cell wall was clearly formed inside the primary cell wall and a part of the organelles were disappeared.Subsequently, the secondary cell wall was thickened rapidly.The average thickness increased around 0.139μm per day from 30 DPA to 40 DPA and around 0.470μm per day from 40 DPA to 50 DPA.The secondary cell wall gradually thickened and formed daily growth rings.Then the cavum inside fiber cell became a narrow gap as the fiber maturing.Results showed that the fiber development process of cotton was quite similar to other varieties reported.The mature fibers were observed by using fluorescence microscopy.Results showed that cotton fiber, especially the cut ends clearly showed the green-blue auto-fluorescence indicative of phenolics in secondary cell wall of cotton fiber.In addition, the lignin was existent in different variety of mature cotton fiber was confirmed by three biochemical methods, including Klason, thioglycolate, and acetyl bromide methods.The residues extracted by Klason method from cotton fiber were similar to the residues from cotton stem and pine stem.The UV absorbance spectra of cotton fiber thioglycolate extracts was quite similar to that of lignin.Results showed lignin existence in mature cotton fiber.At the same time, the biochemical methods were adapted to be suitable for analysis lower lignin cotent in cotton fiber.Finally, we analyzed the contents of lignin in development fiber samples using three methods.The results showed that lignin content was reduced with the development of cotton fiber by per unit of cotton fiber weight.However, by per unit fiber weight of a single cotton boll, the lignin content was increased with the cotton fiber development.Thus lignin content in per unit fiber weight of a single cotton boll is clearly better to explain the realistic condition.Compared with lignin accumulation and secondary wall thickness observed by ultra-structure, we found the same increasing trend.In other words, the lignin deposition was associated with cellulose synthesis.