Single Fiber Strength Variations of Developing Cotton Fibers: Among Ovule Locations and Along the Fiber Length

Abstract

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). Variations along single fibers and among locations on ovules are examined on developing and mature cotton fibers sampled from ovules located in the middle of the locules of the first-position bolls. The breaking force and elongation of the midsection of the fibers from the medial portion of these ovules, in either hydrated or dried state fibers, show the most significant increases 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 midsections of the single fibers are highest, while the breaking forces for fiber sections closer to the basal or tips are similarly lower at all stages of development. Fibers from the medial sections of the ovules have the highest tenacities, followed by those from the micropylar and chalazal ends. Of the mature fibers, the ribbon widths of fibers from the medial sections and the micropylar ends of the ovules are similar, but the medial sections are higher than the micropylar ends. Fibers from the chalazal ends are narrowest and have the lowest linear 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 strength.Cotton fiber quality has a direct impact on the market value of the fibers and the quality of cotton products. The most essential cotton fiber qualities related to mechanical processing (yarn spinning, weaving, and knitting) are fineness, length, and strength. For chemical processing such.as scouring, dyeing, and finishing, chemical compositions and fiber structure play major roles. These fiber quality traits depend on both varietal (genetic) and growing (environmental and developmental) factors.Cotton fibers, which are single-celled outgrowths from individual epidermal cells on the outer integument of the ovules or seeds in the cotton fruit, develop over four stages: initiation, elongation, secondary wall thickening, and maturation. The initiation of fibers begins from the epidermal cells on the ovule surface, followed by the elongation and formation of the primary cell wall. Elongation of the primordial fiber cells starts on the day of anthesis and continues until reaching the final fiber lengths in about 20 to 25 days. Studies on cellulose synthesis show that secondary wall synthesis starts at around 15 to 22 days post-anthesis (dpa), overlapping with fiber elongation [ 1, 10, 11 ], and continues for 30 to 40 days. Fiber maturation is evidenced by the desiccation of the fibers and the collapse of the cylindrical cell...

Single Fiber Strength Variations of Developing Cotton Fibers—Strength and Structure of G. hirsutum and G. barbedense

“…The primary cell wall appears to contribute two-thirds or more of the fiber's strength. These strength estimations are consistent with a report on 14 dpa G. hirsutum Delta Pine 61 fibers, whose breaking tenacity was slightly more than half of fibers that were 49 dpa [ 1 ].In our investigation of how strength develops in cotton fibers and the structure-strength relationships of developing fibers, we have observed large variations in the strengths of developing fibers of any given age [2][3][4][5][6]. We have minimized the sources of fiber strength variations by using first-position (closest to the main stem) bolls between the fourth and the twelfth fruiting branches, using the fibers from the medial section of the most developed ovules from each boll, and by measuring only the middle section of each fiber [3].…”

“…In our investigation of how strength develops in cotton fibers and the structure-strength relationships of developing fibers, we have observed large variations in the strengths of developing fibers of any given age [2][3][4][5][6]. We have minimized the sources of fiber strength variations by using first-position (closest to the main stem) bolls between the fourth and the twelfth fruiting branches, using the fibers from the medial section of the most developed ovules from each boll, and by measuring only the middle section of each fiber [3].…”

“…This sampling approach targets the fibers that represent each of the developmental stages most closely. For G. hirsutum, i.e., SJ-2 [3] and Maxxa [4][5][6], single fiber breaking force (both hydrated and dried) and elongation increase with fiber development. The most significant increases occur during the fourth week of development.…”

Understanding the variability of vegetable fibres: a case study of harakeke (Phormium tenax)

“…7,9,15,18,20,22,23 The effect of developmental stage or age of the plant part harvested on fibre tensile properties has been investigated for a number of plant species. 3,4,7,8,10,24,25 In bast and leaf species, fibre tensile properties tend to increase with distance from the meristem of the plant, at a number of structural levels. For example, 'fibre elasticity E 0 ' (measured using dynamic mechanical thermal analysis) of kenaf (Hibiscus cannibus) bast fibre reportedly increased from the apex of the plant stem (youngest plant tissue) to the base (oldest plant tissue) 25 .…”

Variation in maturity observed along individual cotton fibers using confocal microscopy and image analysis

“…Hsieh and Wang show there can be variations in strength within a single fiber, which can be attributed to maturity among other factors. 11 However, no work has specifically examined maturity in a manner that could be used to corroborate Shahriar et al's findings. It is this intrafiber variability in maturity that we wish to explore via an independent measuring method.…”