Fiber Properties and Carbohydrate and Nitrogen Levels of Cotton Plants as Influenced by Moisture Supply and Fruitfulness.

As distinct from the cereal crops and the spring-flowering fruits, which are characterized by a reproductive climax, cotton is like the tomato and cucurbits in its indeterminate growth; but it is different in the minor extent to which fruit size is influenced by environment and fruitfulness. In a regional variety study (3), 16 varieties of cotton planted during each of three years at eight locations showed locational variations in the varietal means of only 8%c in fiber length, 6%c in fiber weight-per-inch and 9%0 in fiber strength. In terms of use value, however, such differences have high significance. The tendency toward uniformity in the bolls of cotton is accounted for by the extent to which young bolls are shed as the plant becomes heavily fruited. Within varieties and environments, the number of developing bolls per unit of vegetative weight (11) has been found to be remarkably uniform. From California irrigation experiments, ADAMS et al. (1) record that reductions in water supply result generally in losses in staple length (usually within 1/32 inch), seed index (usually within 1.0 gram) and lint index (usually within 0.5 gram). Drought has been observed to decrease the length of cotton lint (2, 5, 18); with this effect, an increase in fiber strength was usually found. BERKLEY et al. (4), as well as others, have associated the increased strength of fibers with a narrowing of the angle of the cellulose crystallites (x-ray angles). Increased nitrogen supply has been found to result in some increase in length of fiber (7, 16, 19). On the other hand, little effect upon length was found by STURKIE (18), whereas, in the presence of inadequate supplies of some other elements, BROWN (6) reported length reductions to result from nitrogenous fertilizers. As has been the general experience with other plants, WADLEIGH (19) found increased nitrogen supply to result in lower carbohydrate accumulations. He associated as causal the plus and minus changes in carbohydrate or nitrogen with the changes in boll properties and in fiber length that corresponded in sign. CROWTHER (7) and NELSON (16) have shown phosphate to increase boll size but not to alter fiber properties. Nelson also found that potash additions which greatly increased yield also increased fiber length and weight per inch; the x-ray angles were increased and the strength of fiber and yarn decreased. YOUNGE (20) has shown sulphur deficiency that reduced boll production had little effect on fiber properties.