Super-Structural Studies Of Fiber Development In Cotton

As an important textile material, cotton fibers play an important role in our national economy and people's lives. So far, great progress has been made in cotton quality breeding in our country, but the improvement of fiber strength still lags behind. The timing, pattern, and extent of deposition of cellulose represent the major factors that ultimately determine the fiber strength based on harmonious development of fiber elongation and secondary cell wall synthesis. Therefor two sets of materials are utilized in this study. One set comprises four genotypes with normal fiber but differ in fiber strength; the other set comprises several cotton mutants of fiber. Ultrastructure and superficial structure of fiber differentiation, protuberance, elongation and mature are observed by SEM or TEM with a view to reveal the structural mechanism of fiber differentiation and elongation, and to analyze main structural factors related to fiber strength. The main results are as follows:1. It showed that consistency of dynamic variation of ultrastructure of four genotypes with different fiber strength and normal fibers resulted from elongation of the epidermal cells of the ovule, because the dynamic variation offered matter and energy that were indispensable to elongation of the epidermal cells of the ovule.2. The main structural factors influenced fiber strength were analyzed by grey relational grade. The results were divided into four levels. Firstly, relation of fiber length and strength was the largest, and the relational degree exceeded 90%. Helix angle and crystal extent took second place, and the relational degree of those versus fiber strength was between 80% and 90%. Cell wall thickness and micromaire followed, and the relational degree of those versus fiber strength was between 70% and 80%. Finally, the relational degree between convolution number and fiber strength was under 40%.3. Three instances existed in the ultrastructure study on the primary development of fiber of different mutants. ( i )The ultrastructure variation of fuzzless-lintless mutant Xuzhoul42 was similar to that of fuzzless-lintless mutant Xin. (ii)The ultrastructure variation of mutants Lil and Li2 with fuzz-supershort lint was basically alike. (iii)The minority epidermal cells of the ovule in the ultrastructure variation of normal genotype TM-1 differed from that of fuzzless-lintless mutants Xuzhoul42 and Xin, and the ultrastructurevariation of the majority epidermal cells of the ovule was similar to that of fuzzless-lintless mutants Xuzhoul42 and Xin. The majority epidermal cells of the ovule were supposed to the undifferentiated epidermal cells of the ovule or latent fuzz cells. 4. Three instances also existed in the superficial structure of different fiber mutants. ( i )Wild type Xuzhoul42 had a temporal and spatial characteristic of fiber differentiation and protrusion, (ii) It was not absolute that fuzzless-lintles mutant Xuzhoul42 did not have protrusions before or after anthesis. Once in a while one or two protrusions occurred in one or two ovules. Three days post anthesis an ovule having a great many protrusions was found actually, but in comparison with wild type Xuzhoul42, its development was obviously slow at the same time. (iii)For fuzzless-lint Xin mutant, the time of fiber protrusion was a little later compared with wild type Xuzhoul42; the number of fiber protrusion was a little fewer compared with wild type Xuzhoul42 at the same time.