Structural Analysis of Fiber Attachment to Seed Coat: Restrictive Barriers to Fiber Removal During Saw Ginning

E.L. Vigil, W.S. Anthony, E.P. Columbus, E. Erbe and W.P. Wergin


When lint cotton is saw-ginned, fewer full-length fibers are removed than with hand-ginning. This results, in part, from breakage of long fibers at distances away from the seed coat surface during ginning with a subsequent increase in the short fiber percentage. In the present comparative investigation, the fine structural anatomy of seed coat - cotton fiber attachment was examined with transmission and cryoscanning electron microscopy. Seed samples from unginned, saw-ginned and hand-ginned lint cotton were examined. Results indicate that lint fibers are secured in the epidermal layer of the seed coat by the compressing action of thick-walled, neighboring cells. This effectively wedges the basal or shank region of lint fibers in the epidermis with the basal region of the cell rearranged into a foot-like process. At the junction of the lint fiber to the seed coat surface there is an angular region or elbow, containing thick primary cell wall material that apparently adds to the strength of fiber attachment to the seed coat. A wax layer covers the entire seed coat surface and is continuous along the surface of all fibers. The wax layer provides a protective coat for seed coat and fibers and may be a barrier to aqueous solutions entering the epidermal cells. Removal of full-length, lint fibers at the seed coat surface during saw ginning results in a clean separation of the fibers from the wax layer and secondary cell wall at the elbow junction. Differences in orientation of secondary cell wall microfibrils of some fibers are clearly seen across the cut surface with a smooth pattern on the outer half and a ragged region toward the center. These findings suggest that improvement of the percent of full-length lint fibers during saw-ginning by special pretreatments would require loosening the wax and cell wall material at the elbow junction of lint fiber to seed coat surface. Supported in part by grants from Cotton Incorporated and National Cotton Foundation.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pg. 1751
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998