The relationships between leaf and petiole potassium (K⁺) concentration, leaf photosynthesis (Pn), and sugar content were studied in field- and greenhouse-grown cotton (Gossypium hirsutum L.). Differing rates of soil K⁺ were applied in order to modify the K⁺ content of the crop. Two weeks after first white flower approximately 100 uppermost first-position sympodial leaves were dated with jewelers tags in each field plot on the day they unfolded. Photosynthetic activity was measured on leaves of similar age beginning two weeks after tagging at weekly intervals for five weeks. After each Pn measurement, the leaves and their corresponding petioles were removed from the plant and analyzed for plant K⁺. A portion of the leaf material was reserved for sugar analyses. Greenhouse studies were conducted in order to obtain more consistent results from the sugar analyses.

Cotton was grown in large pots with differing amounts of soil K⁺. First position flowers were dated on the day of anthesis. Leaves subtending the dated flowers were analyzed for sugars and plant K⁺ at different stages of maturity. Leaf Pn did not vary across the soil K⁺ levels in the field experiments. Leaf and petiole K⁺ levels, however, did show trends across the different soil K⁺ levels that suggested more soil K⁺ resulted in more plant K⁺. Sugar data taken from the field were variable and did not exhibit any clear patterns. Greenhouse-grown cotton leaves showed similar trends with respect to leaf and soil K⁺. Sugar analyses suggested more plant K⁺ resulted in less leaf glucose, fructose, and sucrose and more starch. This work will continue with additional emphasis on sampling and carbohydrate analysis.