Single fiber strength variations of developing cotton fibers: Among ovule locations and along the fiber length

This paper, the first in a series on variations in single fiber properties of developing and 'mature cotton, focuses on single fiber tensile property variations of greenhouse-grown developing G. hirsutum (Maxxa variety). Vari ations along single fibers and among locations on ovules are examined on de veloping and mature cotton fibers sampled from ovules located in the middle of the locules of the first-position bells. The breaking force and elongat ion of the midsection of the fibers from the medial portion of these ovules , in either hydrated or dried state fibers, show the most significant incre ases during the fourth week of development. As fibers develop beyond 30 dpa , the single fiber breaking forces, linear densities, and tenacities become scattered. The forces required to break the mid-sections of the single fib ers are highest, while the breaking forces for fiber sections closer to the basal or tips are similarly lower at all stages of development. Fibers fro m the medial sections of the ovules have the highest tenacities, followed b y those from the micropylar and chalazal ends. Of the mature fibers, the ri bbon widths of fibers from the medial sections and the micropylar ends of t he ovules are similar, but the medial sections are higher than the micropyl ar ends. Fibers from the chalazal ends are narrowest and have the lowest li near densities. The tenacities of single fibers from the medial regions of the ovules are higher than those from the chalazal and micropylar ends, the latter two being similar. Ultimate fiber tensile properties are reached in the developing fibers by 30 dpa; further fiber development contributes to thicker cell walls and thus to fiber mass, but not to intrinsic fiber stren gth.