Characterization of Cellulose in Developing Cotton Fibers

During our investigation of cotton fiber development and cellulose the cellulose fraction of DP-50 fibers at ages 21, 25, 30, 38, 44 and 56 days post anthesis (DPA) has been subjected to sequential 6N HCl degradation. Long accepted data demonstrates the initial release of a large amount of glucose which then slows down over time. The stated explanation is that the non-crystalline material is released rapidly but the crystalline material takes much longer to be released. That would imply a difference in the material remaining. Light microscopy of the remaining residue of each successive hydrolysis does not appear to support that conclusion. In each case there just appears to be less material but microscopically it looks the same. The cellulose particles appear to either be present or to disappear but no visible change has been observed. There do appear to be two significant differences between the cellulose of developing fibers and mature cotton fibers. Two groups of glycans which elute after about 12 minutes on HPAEC chromatograms of the developing fibers appear to have a much greater relative abundance at all ages than the corresponding glycans from the cellulose of mature fibers. These glycans have been found to yield several amino acids on hydrolysis. Another difference between the cellulose of developing fibers and that of mature fibers is that at the end of the sequential hydrolyses there is simply nothing left of mature fibers while the developing fibers yield a series of cello-oligosaccharides in their final hydrolysis. The significance of these differences is not known at this time but there are apparent differences between developing fibers and fully mature cotton which involve even the cellulose which was synthesized much earlier. Although 56DPA cotton is often considered to be mature, changes are still occurring in the fibers.