Green Cotton Fiber Research Articles

Survey of Red, Green and Blue Cotton Fibres

ABSTRACTThe ability to discriminate between red, green and blue cotton fibres from various sources by comparing the microscopic characteristics and fluorescent properties (comparison microscopy) and visible spectra (microspectrophotometry) of the fibres in each colour group was assessed. A summary of the discriminating ability of each technique applied separately and both in combination is presented.

Changing the Dimensions of Suberin Lamellae of Green Cotton Fibers with a Specific Inhibitor of the Endoplasmic Reticulum-Associated Fatty Acid Elongases.

The fibers of the green lint mutant of cotton (Gossypium hirsutum L.) contain large amounts of wax and are suberized. More than 96% of the bifunctional aliphatic suberin monomers ([alpha],[omega]-alkanedioic acids and [omega]-hydroxyalkanoic acids) have chain lengths of C22 and C24 in green cotton fiber suberin. In fibers grown in the presence of S-ethyl-N,N-dipropylthiocarbamate (EPTC), a specific inhibitor of the endoplasmic reticulum-associated fatty acid elongases, the aliphatic suberin monomers were shortened to chain lengths of C16 and C18. Whereas the amounts of most suberin monomers were not negatively affected by the inhibitor treatment, the amounts of [alpha],[omega]-alkanedioic acids and of glycerol were reduced by more than 80%. Analysis in the transmission electron microscope showed a reduction in suberin content after EPTC treatment. The suberin layers were discontinuous and consisted of fewer lamellae than in the controls. A small proportion (up to 22%) of the electron-translucent suberin lamellae were thinner after EPTC treatment, probably because of the shortening of the aliphatic suberin monomers. A larger proportion of the electron-translucent lamellae were thicker than the lamellae in the controls. Possible explanations for this observation are discussed.

Caffeic acid and glycerol are constituents of the suberin layers in green cotton fibres

The fibres of the green-lint mutant (Lg) of cotton (Gossypium hirsutum L.) are suberized and contain a large proportion of wax. The unidentified components of the wax were separated into a colourless fluorescent fraction and a yellow pigmented fraction. Using ultraviolet spectroscopy and nuclear-magneticresonance ((1)H-NMR) spectroscopy, esterified trans-caffeic acid was identified as the only phenolic component in the colourless fraction. This fraction was further purified and was shown to contain caffeic acid esterified to fatty acids (mainly ω-hydroxy fatty acids), and glycerol in molar ratios of 4∶5∶5. When 2-aminoindan-2-phosphonic acid (AIP), an inhibitor of phenylalanine ammonia-lyase (EC 4. 3. 1. 5.) was added to ovules cultured in vitro, at the beginning of secondary wall formation, the fibres remained white and the colourless caffeic-acid derivative and the yellow compounds could no longer be detected by ultraviolet spectroscopy. Fibres grown in the presence of AIP were also examined in the electron microscope. Secondary cell walls were present in the treated fibres, but the electron-opaque suberin layers were replaced by apparently empty spaces. This result indicates that cinnamic-acid derivatives are covalently linked to suberin and have a structural role within the polymer or are involved in anchoring the polymer to the cellulosic secondary wall. Purified cell walls of green cotton fibres contained about 1% (of the dry weight) of bound glycerol, 0.9% of the glycerol being extractable with the wax fraction and 0.1% remaining in the cell-wall residue. The corresponding values for white fibres were 0.03% (total), 0.02% (wax), and 0.01% (cell-wall residue). Fibres synthesizing their secondary walls in the presence of AIP contained about normal amounts of bound glycerol in the wax fraction, but glycerol accumulation in the cell-wall residue was inhibited by about 95%. These observations indicate that glycerol is an important constituent of cotton-fibre suberin. Considerable amounts of bound glycerol could also be determined in exhaustively extracted cell walls of the cork layer of potato periderm (1.2%) and smaller amounts in the outer epidermal cell wall of Agave americana L. leaf (0.1%) indicating that the presence of glycerol in suberins and possibly also in cutins may be more widespread than previously thought.

Ultrastructure and chemistry of soluble and polymeric lipids in cell walls from seed coats and fibres of Gossypium species

Electron-microscopic examination in conjunction with extraction procedures and chemical analysis have confirmed that a suberin-like lipid biopolymer is located within the concentric polylamellate layers found in the secondary cell walls of green cotton fibres (Gossypium hirsutum cv. green lint). A polymer of similar ultrastructure and chemical constitution also occurs mainly in the secondary seed-coat walls of the outer epidermis of both green and white varieties of G. hirsutum. The suberins composed of predominantly C22 compounds are, however, markedly different from those present in the periderms of the same plants; these comprise mainly C16 and C18 compounds. Long-chain 1-alkanols (C26-C36) and alkanoic acids (C16-C36) are the principal components of the wax from white fibres but these lipid classes comprise a much smaller proportion of that from green fibres. unidentified highmolecular-weight compounds were the major constituents of the green-fibre was extract which also contains a number of yellow-green pigments, probably flavonoid in nature. These pigments are thought to be associated with the ultrahistochemical reaction with silver proteinate that was observed only in the green-fibre cell walls. A total of 16 wild and cultivated cotton species were examined with the electron microscope for the presence of suberin. The outer seed-coat epidermis of all the examined species but only the fibres of the wild ones were found to be suberized. Among the analysed mutants of fibre colour in G. hirsutum only the gene Lg (green lint) seemed to be associated with suberin.

Ultrastructural and Chemical Evidence That the Cell Wall of Green Cotton Fiber Is Suberized

Green cotton (Gossypium hirsutum L.) fibers were shown by electron microscopy to have numerous thin concentric rings around the lumen of the cell. These rings possessed a lamellar fine structure characteristic of suberin. LiA1D(4) depolymerization and gas chromatography-mass spectrometry analysis showed the presence of a suberin polymer in the green cotton with the major aliphatic monomers being omega-hydroxydocosanoic acid (70%) and docosanedoic acid (25%). Ordinary white cotton was shown by chemical and ultrastructural examination to be encircled by a thin cuticular polymer containing less than 0.5% of the aliphatic components found in green cotton.