Starch Depletion and Sugars in Developing Cotton Leaves

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Abstract
Cotton plants (cv. ''Coker 100'') were exposed to a 14-h dark period. Starch degradation occurred with no accumulation of sugars due mainly to translocation. Considerable amounts of starch degradation products however were detected from leaves after phloem transport was blocked. A minor component (10-25% of total starch) with a linear structure, amylose, was preferentially degraded, whereas the major multiple-branched component (about 80%), amylopectin, showed an increasing resistance to degradation with leaf age. This relationship was also shown by the decreasing iodine-binding capacity of unit starch with increasing leaf age. The structural resistance of amylopectin to enzymic dark degradation was one of the barriers to starch dissolution in cotton.