CARBOHYDRATE STATUS OF NARROW ROW COTTON AS RELATED TO VEGETATIVE AND FRUIT DEVELOPMENT

Plant dry weights and total available carbohydrates (TAC) were compared during 2 seasons in narrow row cotton [Gossypium hirsutum L.] planted at population densities of 7.4, 14.8 and 22.2 plants/m2. Although large differences occurred in plant size, TAC levels among the 3 populations were similar during the various sampling dates. TAC had a cyclic pattern with low levels during mid-season. This depression coincided with a rapid increase in fruiting form weight when lint yields were high and with a rapid increase in vegetative weight when lint yields were low. This excessive vegetative growth can effectively compete with fruiting forms for TAC. In a related experiment, TAC levels along plant axes were lowest near the central part of the plant where developing bolls were located. This shows that the TAC depression can be relatively localized within plants suggesting that photosynthates are not effectively translocated from the top to the central part of the plant. Restructuring of the plant canopy to allow more solar radiation penetration to leaves near developing bolls and/or selecting for more efficient translocation from upper leaves to developing bolls should help increase yields.