X-ray diffraction and FTIR investigations of cellulose deposition during cotton fiber development

The structure and organization of cellulose in developing cotton fibers harvested from two cultivars of Gossypium hirsutum L. (Texas Marker-1 and TX55) at varying developmental stages from 10 to 56 days post anthesis (dpa) were investigated using wide-angle X-ray diffraction (WAXD) and Fourier transform infrared (FTIR) spectroscopy. During fiber development, the percentage crystallinity and crystallite size normal to the 200 plane increased while the full width at half maximum (FWHM) decreased. This indicates an increased alignment and decreased molecular disorder along the 200 plane as cellulose biogenesis progresses. The evolution of the WAXD parameters as a function of developmental stages provided information on the transition from the primary cell wall to the secondary cell wall and, thus, could indicate the rate of cellulose macromolecules deposition and organization during cellulose biosynthesis. These results were further confirmed by FTIR and cellulose content data. Indeed, IR ratios, cellulose content, and the integrated intensities of the vibrations 667 and 897 cm ⁻¹ showed good correlation with the percentage crystallinity. These parameters could be used as good indirect estimators of the percentage crystallinity in developing cotton fibers.