Cotton fiber cell-wall studies

The fiber saturation point (FSP) of cotton is the total amount of water present within the cell wall expressed as a ratio of water to solid content. It is equivalent to the water of imbibition of the fiber, also called its water retention value. The FSP has been measured using solute exclusion, centrifugation, porous plate, and hydrostatic tension techniques. It occurs at RVP greater than 0.997 and from the review of the papers, it has been concluded that the studies have yielded a value for FSP in the range of 0.43 to 0.52 g/g [303]. 

Direct measurements of cellulose orientation in fibers have yielded conflicting results. Evidence from x-ray diffraction studies of wood samples suggested that the cellulose crystallites are arranged randomly in the plane perpendicular to the fiber axis (30-33). Raman spectroscopic studies of cotton fibers dried under tenTTon, however, demonstrated that the methine C-H bonds are oriented preferentially perpendicular to the surface of the cell wall (34). Since the C-H bonds are perpendicular to the 002 plane, the orientation suggested by the Raman evidence differs from the alternating orientation in algal celluloses. 

Seagull R.W. 1992. A quantitative electron microscopic study of changes in microtubule arrays and wall microfibril orientation during in vitro cotton fiber development. J Cell Sci 101 561-577. 

Articles on x-ray diffraction measurements of orientation in this period were concerned with the orientation of cellulosic chains in fibers and in cell walls (29-33). A study of cotton, wood, flax, sisal, hemp, and other cellulosic structures established the occurrence of helically oriented cellulosic materials. Naturally occurring cellulose membranes were also investigated. Simon (32) proposed the use of pole figures, ie, stereographic projection of normals to crystallographic planes, to represent the orientation of the chains of crystalline cellulose (32). The development of uniaxial and uniplanar orientation was described based on the x-ray results. 

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