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Starch depletion and sugars in developing cotton leaves.
1United States Department of Agriculture, Science and Education Administration, Agricultural Research, Western Cotton Research Laboratory, 4135 East Broadway Road, Phoenix Arizona 85040.
Plant Physiology
|May 1, 1980
Summary
Cotton plants degrade starch during dark periods, primarily through translocation. Amylose is degraded preferentially over amylopectin, which becomes more resistant with leaf age, hindering starch dissolution.
Area of Science:
- Plant physiology
- Biochemistry
- Molecular biology
Background:
- Starch metabolism is crucial for plant energy storage and mobilization.
- Understanding starch degradation pathways is essential for crop yield optimization.
Purpose of the Study:
- To investigate starch degradation and sugar translocation in cotton plants under extended dark periods.
- To determine the differential degradation rates of starch components (amylose and amylopectin).
Main Methods:
- Exposure of cotton plants (cv. Coker 100) to a 14-hour dark period.
- Blocking phloem transport to assess translocation of starch degradation products.
- Analysis of starch component structure and iodine-binding capacity in relation to leaf age.
Main Results:
- Starch degradation occurred without significant sugar accumulation, mainly due to translocation.
- Starch degradation products were detected in leaves even when phloem transport was blocked.
- Amylose (linear component) was preferentially degraded, while amylopectin (branched component) showed increased resistance with leaf age.
- Decreasing iodine-binding capacity of starch correlated with increasing leaf age.
Conclusions:
- The preferential degradation of amylose and increasing resistance of amylopectin with age are key factors in cotton starch metabolism.
- Structural properties of starch components influence their susceptibility to degradation.
- Enzymic resistance of amylopectin presents a barrier to starch dissolution in cotton leaves.