Applying microscopy to the development of a reference method for cotton fiber maturity

Two microscopic methods for characterizing the maturity of a cotton sample have been developed, using either cross-sectional or longitudinal scanning of fibers by image analysis. This study compares the two methods for consistency with the aim of opti mizing their efficiency and accuracy as reference methods. Longitudinal scans of cotton fibers at immature (3.5 weeks post-anthesis) and mature (7 weeks, field opened) growth stages are compared with cross-sectional measurements of the same fiber samples. Maximum projections along the length of cotton fibers agree with cross-sectional mea surements, but minimum projections do not. Variations in fiber twisting and folding render minimum width projections inaccurate. The only true measure of wall thickness is from cross-sectional data, and fiber alignment is critical. Sample preparation for developing a reference method dictates that bundles of combed, parallel fibers be sectioned in the center. This procedure will decrease errors in sampling due to the natural taper of the fiber along its length.