Relationships of Chlorophyll and Enzyme Gradients to Sucrose Content of Sugarcane Leaves

Abstract

The distribution of sucrose, chlorophyll, ß-amylase and ATPase was examined in sugarcane leaves of different rank sampled at different hours of the day. Leaf ranks —2 to +7 were detached at 0600, 0800, and 1330 hours and segmented into 30-cm portions from base to apex prior to analysis. Positive basipetal sucrose gradients were found in all ranks with maximum values at 1330 hours. Inverse gradients (acropetal) were obtained for chlorophyll, with large decreases between 0600 and 0800 hours in blade segments most exposed to light, ß-amylase activity was inversely related to sucrose content between leaf ranks, and positively related from apex to base of individual blades. Pronounced increases occurred between 0600 and 0800 hours which appeared to be independent of changes in light intensity or chlorophyll content. Both ß-amylase and ATPase were exceptionally active in the youngest leaf rank (—2), particularly in the darkened lower half. In mature leaves (+1 to +7) ATPase activity was essentially constant relative to gradient, rank, and diurnal parameters. Important enzymic roles in foliar sucrose movement are suggested by the data. These are discussed in terms of polyglucoside hydrolysis and regulation of energy expenditure for sugar transport processes.