Bolls from four cottons, one from each of the cultivated species G. arboreum, G. herbaceum, G. barbadense, and G. hirsutum, were picked at weekly intervals. Crosssectional area and perimeter were determined for 200 fibers of each of these samples, and secondary wall thickness and circularity were calculated. Cross-sectional area, circularity, and secondary wall thickness increased with fiber growth. These increases were greater in the initial stages of development than in the later stages. The percentage of frequency distribution of cross-sectional area, perimeter, and secondary wall thickness indicated almost normal distribution, but there was no similar trend for circularity.The striking feature of cotton fiber is the variability of nearly every physical character. The cross-sectional shape is no exception, since it may vary from a bean shape to nearly round. Because of this, different methods have been used to classify shape factor for some sort of numerical index. Schloemer [3] was the first to consider shape factor in terms of area and perimeter, since obviously any variation in shape factor is mainly due to a variation in these. Chauhan et al.( 1 ] studied the variation in fiber characteristics such as perimeter, cell-wall area and thickness, and shape of raw and mercerized cotton fibers. In order to investigate changes in these parameters as a function of growth, these authors presented data on perimeter, cell-wall thickness, and cell-wall area of one cotton, Kalyan, and they observed that these fiber characteristics followed normal distribution for all three different growth periods. Similar work was initiated at the Cotton Technological Research Laboratory, Bombay, during 1972, and many aspects of shape factor were studied exhaustively. One of the aspects studied in detail was the change in circularity of fiber cross sections of cottons picked from the bolls of different species during the development period. The data regarding perimeter, cross-sectional area, circularity, and wall thickness are analyzed and presented here. . Experimental ..The cottons selected were AK.235 (G. arboreum), Digvijay (G. herbaceum), Gujarat 67 (G. hirsutum), and ERB.4530 (G. barbadense). Bolls of these cottons were picked at weekly intervals ending at 28, 35, 42, 49, 56, and 63 days after flowering and preserved under 4% formalin solution. (Note that for two of the cottons, AK.235 and ERB.4530, the bolls of 63 days were not available, while for three of the cottons, Digvijay, Gujarat 67, and ERB.4530, the cross sections for 28 days could not be taken because the fibers had become entangled upon dehydration.) Fibers from cotton bolls were dehydrated at room temperature and the cross sections were obtained with a Hardy microtome modified according to Schwarz and Shapiro [4]. The cross sections were magnified to 1350X under a microscope fitted with a Euscope and a ground glass screen. The circularity (C) was determined using Schloemer's formula [3], C = 4aA/P2, where A is the cross-sectional area measured with a polar plan...
Changes in cross-sectional dimensions of cotton fibers resulting from crosslinking treatments were studied. One variety of cotton, Sujata, was subjected to crosslinking in dimethyloldihydroxyethyleneurea and in formaldehyde to different add-on levels. The changes in cross-sectional area and perimeter due to crosslinking, as well as the changes in these dimensions resulting from subsequent wetting, were measured. The results were discussed in the light of available information on fiber morphology and the nature of crosslinking reactions.
An attempt has been made to examine the cross-sectional shapes of the cotton fiber along its length. For this purpose, three cottons were selected, and the cotton fibers were sectioned at four different positions— viz., one each at the two extremities (basal and apical ends), and two at the middle region. The values of circularity of the cross sections at these regions were determined from measurements of area and perimeter. It was concluded that the apical end of the cotton fiber was more circular in cross-sectional shape, and the basal end less circular than the middle region. The middle region was consistent in cross-sectional shape over a considerable length. Further, the lower value of the cross- sectional shape at the basal end was confirmed from measurement of fiber and lumen widths of the fiber.
Forty varieties of cotton, ten from each of the four commercially cultivated species, G. arboreum, G. herbaceum, G. barbadense, and G. hirsutum, at two fiber maturity levels of 60% and 75% were examined for differences in their cross-sectional shapes. The fibers were classified into three different categories of cross-sectional shape, round (circularity value above 0.80), elliptical (circularity value between 0.80 and 0.50), and flat (circularity value less than 0.50), as per ASTM standards. G. arboreum and G. herbaceum (Old World cottons) had a greater percentage of fibers of round cross- sectional shape at both the fiber maturity levels than G. barbadense and G. hirsutum (New World cottons) indicating that the cross-sectional shape may be a varietal characteristic. The differences in the cross-sectional shape of fibers among the cottons of different species were further confirmed from the data obtained on the circularity of fibers at various stages of development for cotton bolls of each of the four species.
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