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Title: CHEMICAL STRUCTURAL INVESTIGATION OF THE COTTON FIBER BASE AND ASSOCIATED SEED COAT: FOURIER-TRANSFORM INFRARED MAPPING AND HISTOCHEMISTRY

Author
item HIMMELSBACH, DAVID
item KIM, JUHEA - DEPT OF TEX MER INT UGA
item AKIN, DANNY
item HARDIN, IAN - DEPT OF TEX MER INT UGA

Submitted to: Textile Research Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/2002
Publication Date: 1/1/2003
Citation: HIMMELSBACH, D.S., KIM, J., AKIN, D.E., HARDIN, I.R. CHEMICAL STRUCTURAL INVESTIGATION OF THE COTTON FIBER BASE AND ASSOCIATED SEED COAT: FOURIER-TRANSFORM INFRARED MAPPING AND HISTOCHEMISTRY. TEXTILE RESEARCH JOURNAL. 2003. V. 73. P. 281-288.

Interpretive Summary: Lack of knowledge of the structural-chemical phenomena that affect the fiber to seed coat bonds in cotton has prevented improvements quality of the final product. This research has elucidated important characteristics in determining fiber-seed interactions by employing microscopic mapping in the mid-infrared spectral region together with histochemical staining. These two complementary techniques were primarily focused on the nature of the chemical components that are associated with cotton fibers at their precise point of attachment to the seed coat. Waxes or long-chain alcohols were detected on the surface of and adjacent to cotton fibers in the outer epidermal tissue in the top, middle and bottom of the cotton seed. Pectate anions were detected in the outer epidermis and pigment layers (significantly surrounding the foot of fibers) and the showed a consistently strong presence in upper palisade layer tissue of all seed regions. The strong presence of carbonyls, other than carboxylate (pectate) anions, were present at the border of the upper palisade and colorless layers of the seed coat. A mixture of the salt and acid/ester forms of pectins were both present in some regions. Lignin type aromatics were indicated in the colorless layer of all regions and tannin or pre- tannin type aromatic structures were indicated in the outer pigment layer and interior to the cells in epidermal layer of all seed coat regions. The synergism generated by the integration of infrared and staining techniques, in this work, provided for confirmation of the results obtained by both and a better understanding of the fiber-seed interactions that are important to the development of methods for improving the quality of processed cotton.

Technical Abstract: FT-IR mapping & histochemical staining were employed to reveal the location & relative importance of chemical components involved with fiber-seed coat interactions. Sections of tissue obtained from chalazal,middle & micropylar regions of the seed were investigated. The IR profile of the 2855 cm-1 band & the Oil Red O stain indicated waxes or long-chain alcohols on the surface of & adjacent to cotton fibers in the outer epidermal tissue in al regions of the cotton seed. The IR profile of the ratio of the 1605/1640 cm-1 bands & staining with Ru Red indicated the sporadic presence of COOin the outer epidermis & pigment layers (significantly surrounding the foot of fibers) & their strong presence in upper palisade layer tissue of all seed regions. The C=O band profile at 1734 cm-1 indicated a strong presence of other types of C=Os, at the border of the upper palisade & colorless layers, to some extent in the outer epidermal layer & weakly to not at all in the outer pigment layer. In the epidermal layer a shoulder on the primary C=O band & appeared at 1715 cm1 that indicated the presence of a different C=O, likely associated with waxes. This result was also complemented by Ru Red staining suggesting a mixture of the salt & acid/ester forms of pectins were present where the 1605 & 1734 cm-1 profiles overlapped. An IR profile was generated at 1512 cm-1 that was the mid-point of a doublet formed by overlapping bands & with centers at 1510.5 cm-1 & 1513.5 cm-1. Lignin-type aromatics were indicated by the acid phloroglucinol stain in the colorless layer of all regions of the seed coat & gave an increased IR absorbance at 1510.5 cm1. Tannin-type structures were indicated by vanillin-HCl stain in the outer pigment layer & interior of the cells in epidermal layer of all seed coat regions with more intense