Morphological Character Of Cotton Fober
Microscopic observation showed that the cotton fibers were flattened and twisted in the longitudinal direction. The closed end was thin, and the one end of the cottonseed was thick and open. The cross section of cotton fibers consists of many concentric layers, including primary layer, secondary layer and central cavity.
_The primary layer is the outer layer of cotton fibers, i.e. the primary part of fibroblasts. The outer skin of the primary layer is a layer of waxy and pectin with deep filamentous wrinkles. The primary layer is very thin with little cellulose content. Cellulose has a helical network structure in the primary layer.
_Under the primary layer of secondary cotton fibers is a thin layer of cells, which are closely packed by microfibrils. The microfibrils are spirally arranged with fibril axes, and the inclination angle is between 25 and 30 degrees. In this layer, there are almost no cracks and holes. The secondary layer is formed by the deposition of cotton fibers during the thickening period, almost all of which are cellulose. Because of the daily temperature difference, most cotton fibers deposit a layer of cellulose day by day, so they can form cotton fibers'daily rings. The deposition of cellulose in the secondary layer is not uniform, but it is spiral in the form of bundles of small fibers and the inclination of fibre axis, and forms a turn along the direction of fibre length, which is the reason why cotton fibers have natural curvature. The development of secondary layer depends on the growth conditions and maturity of cotton fibers, which can determine the main physical properties of cotton fibers.
_After the growth of cotton fibers in the middle cavity ceases, the space left behind in the cell wall is called the middle cavity. The perimeter of primary cells in the middle part of cotton fibers of the same variety is approximately equal. When the secondary cell wall is thick, the middle cavity is small; when the secondary wall is thin, the middle cavity is large. When the cotton boll ripens and splits, the cross section of cotton fiber is round, and the middle cavity is also round. The cross section of the middle cavity is equal to 1/2 or 1/3 of the cross section of the fiber. When the cotton boll splits naturally, the cross section of the cotton fiber is waist-shaped, and the cross section of the middle cavity is flattened. The cross section of the flattened middle cavity is only about 10% of the total fabric.