Carbohydrate content of cotton plants at different growth periods and the influence of fertilizers

The data show that the total sugars, representing the soluble carbohydrates, decreased in concentration in the plant tops between the stages of seedling and square formation, after which the trend in concentration was upward and increased rapidly during active boll formation, the rate of increase diminishing as the bolls approached maturity. At maturity, when the cotton bolls began opening, the total sugars began decreasing in concentration. Excepting the period of active boll formation, when the concentration of total sugars in both the tops and roots was rapidly increasing, the course of the changes in concentration of the total sugars in the roots tended to be opposite to that in the plant top. During the period of study, the concentration of total sugars in the roots exceeded the concentrations in the plant tops. The diose sugars of the roots exceeded by a large margin the concentration of monose sugars. In the tops of the cotton plant the difference in concentration of the two sugars was influenced by the stage of plant development and the fertilizer used. In general, during the latter stage of boll formation, July 9 to August 6, the monose sugars exceeded in concentration the diose sugars. The monose sugars in the tops of cotton plants and the diose sugars in the roots were the best indicator of the effects of fertilization on the soluble carbohydrates. The polysaccharoses, representing the insoluble or storage carbohydrates, were found to occur in greater concentration in the roots than in the tops of the cotton plant. In general, the course of the changes in concentration for both the roots and tops of the plant was upward throughout the growth periods studied. The rate of change in concentration was greater in the plant roots than in the tops. Plants fertilized with complete fertilizers had a higher level of soluble and insoluble carbohydrates in both the tops and roots during the latter stages of plant development than did the unfertilized plants or those fertilized with nitrogen and phosphorus separately. Phosphorus alone tended towards effecting a higher level in the plant tops. Nitrogen alone had no consistent effect upon the soluble carbohydrates in either the tops or roots but did tend to effect a lower concentration of insoluble carbohydrates near the end of the season. The growth of cotton plants and yields of seed cotton were increased by fertilizer applications, the largest returns resulting from the 9-3-3 followed by the 3-9-3 fertilizer. These mixtures also produced most cotton at the first picking, showing an early stimulating effect on growth and square and boll formation, resulting in earlier maturity of cotton. The greater carbohydrate content of the plants correlates with larger plant growth and larger yields. The total carbohydrate content expressed as percentage of green plant or as grams per plant was greatest in plants grown with 9-3-3 and 3-9-3 fertilizers, these being the fertilizers giving largest plant growth and greatest yields.