FIBER PROPERTIES AND CARBOHYDRATE AND NITROGEN LEVELS OF COTTON PLANTS AS INFLUENCED BY MOISTURE SUPPLY AND FRUITFULNESS

Abstract

The effects of restricting the number of bolls per cotton plant to 2 and limiting the water supply were studied in a series of expts. at College Station, Texas, and Shatter, California. Both of the treatments increased CHO levels and N in the plants, but partial defloration did not limit the rate of CHO utilization in vegetative growth and in the remaining bolls, whereas drouth did. Under the 2-boll treatment increases occurred in plant growth, wt. of seed cotton per boll, wt. of 100 seeds, lint on 100 seeds, fiber length, fiber wt. per inch, and fiber maturity. With extra N in the seed, protein synthesis proceeded at the expense of oil synthesis. For the most part, drouth reduced all of these characters; some exceptions were found, particularly in an expt. with the var. Acala pl8, in which water limitation reduced plant growth by 50% but caused no wilting. The 2 treatments increased carbohydrate levels and usually increased fiber strength. Fiber strength represents a formative effect on the fiber cellulose rather than a growth effect. A few measurements indicated an inverse relation between CHO and the orientation of the cellulose crystallites with respect to the fiber axis (X-ray angles). In a 5-var. expt., those making the greatest growth and having the greatest fiber strength had the lowest CHO levels in their stems. Within vars., however, treatments that increased CHO levels also increased fiber strength. The orientation of the polar glucose molecule as it enters the plasma film for polymerization into cellulose is apparently influenced by the intensity of the polar forces of the lint cell; and the intensity of this electrical field evidently varies both with the level of supply and rate of utilization of CHO. CHO levels were much lower in plants grown in California compared with plants in Texas, and fiber strength, length, and weight per inch were also lower; but in plants grown in California the weight of seed cotton per boll, wt. per seed, and lint per seed were higher.