FT-IR examination of the development of secondary cell wall in cotton fibers

Authors: Santiago Cintron, Michael; Hinchliffe, Doug

Submitted to: FIBERS
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2015
Publication Date: 1/29/2015
Citation: Santiago Cintron, M., Hinchliffe, D.J. 2015. FT-IR examination of the development of secondary cell wall in cotton fibers. FIBERS. 3:30-40.

Interpretive Summary: The secondary cell wall development of cotton fibers gathered at 18, 20, 24, 28, 32, 36 and 40 days after flowering of cotton plants was examined using a infrared spectrometer and its light reflectance accessory. Generally, bands determined to come from the cellulose in the cotton fibers showed an increase in intensity in the infrared measurement readout of the cotton fibers. Notably, there was a marked intensity increase for bands at 1002 and 985 cm-1; these bands were determined to correspond to vibrations of carbon-oxygen (C-O) bonds founds in cellulose alcohol groups. However, these bands are unique to less common arrangements of the cellulose alcohols. C-O vibrational bands from dominant conformations and observed at 1104, 1052, 1028 cm-1 undergo a modest intensity increase during secondary cell wall development. Spectra of cotton fibers treated with heavy water did not demonstrate significant changes in their O-H stretching band shapes or positions during development. Only a progressive increase in O-H band intensity was observed. Together, our observations suggest that during cotton secondary cell wall formation less crystalline cellulose is formed along with the highly crystalline components. Some of the cellulosic alcohols in the less crystalline components are found in secondary conformations that give rise to the marked rise in the intensities of the 1002 and 985 cm-1 C-O vibrations. Results also indicate that the highly crystalline cellulose component produced during secondary cell wall formation maintains the hydrogen bonding network observed for the primary cell wall.

Technical Abstract: The secondary cell wall development of cotton fibers harvested at 18, 20, 24, 28, 32, 36 and 40 days after flowering was examined using attenuated total reflection Fourier transform-infrared (ATR FT-IR) spectroscopy. Generally, a progressive intensity increase for bands assigned to cellulose Iß was observed during fiber development, including a marked intensity increase for the C-O vibrations at 1002 and 985 cm-1. C-O vibrational bands from dominant conformations and observed at 1104, 1052, 1028 cm-1 undergo a modest intensity increase during secondary cell wall development. Spectra of deuterated cotton fibers did not demonstrate significant changes in their O-H stretching band shapes or positions during development. Only a progressive increase in O-H band intensity was observed. Together, our observations suggest that during cotton secondary cell wall formation less crystalline cellulose is formed along with the highly crystalline components. Some of the cellulosic alcohols in the less crystalline components are found in secondary conformations that give rise to the marked rise in the intensities of the 1002 and 985 cm-1 C-O vibrations. Results also indicate that the highly crystalline cellulose component produced during secondary cell wall formation maintains the hydrogen bonding network observed for the primary cell wall.