Abstract: In order to explore the reasons for poor quality of colored cotton fiber, the experiments were conducted with five cotton (Gossypium hirsutum L.) cultivars, including Zongxu 1 (ZX1), Xincai 1 (XC1), Longlümian 2 (G-7), Lü 1-4560(4560), and the contrast of white cotton Lumianyan 28 (LMY28). Dynamic changes of super-molecular structure and fiber quality and the relations between them in fiber development process of colored cotton were studied by X-ray diffraction technique. The results showed that the ultimate fiber length, fiber 3.2 mm gauge tenacity, fiber maturation and fiber micronaire of all cotton cultivars ranked as LMY28>ZX-1 and XC-1>G-7 and 4560. The corresponding crystalline grain size increased constantly and orientation parameters diminished gradually in fiber development process, but there were differences among different cultivars. Compared with the white cotton LMY28, ZX-1 and XC-1 had low initial value, too large amplitude and slightly lower termination value for crystalline grain size of fiber; low initial value, small diurnal variation and high termination value for orientation parameters. For G-7 and 4 560 fibers, the initial value of crystalline grain size was low, the increased amplitude was small and the termination value was slightly lower; the initial value of orientation parameters was high, diurnal variation was small and the termination value was high. The crystalline grain size had a correlation with 3.2 mm gauge tenacity (r=0.89621^*), as well as, the orientational distribution angle-ψ (°) and spiral angle-φ (°) had a negative correlation with fiber 3.2 mm gauge tenacity, fiber maturation and fiber micronaire (r= –0.93816^* ~ –0.90233^*), moreover, the orientational separate angle –α (°) had a negative correlation with fiber length (r= –0.97314^**). In conclusion, the poor quality of colored cotton fiber is probably in relation to poor fiber 3.2 mm gaugetenacity, fiber maturation, fiber micronaire, fiber length, resulting from low initial value and termination value of crystalline grain size and high termination value of orientation parameters in fiber development process.

Key words: Colored cotton, Cotton fiber, Fiber quality, Super-molecular structure