Effects of Water Stress on Branching Enzyme Activity and Fine Structure of Cotton Leaf Starch

Chong W. Chang


 
ABSTRACT

Cotton plants (Gossypium hirsutum L.) were subjected to a gradual dehydration until the leaf water potential reached about -2.0 MPa at the end of 5 days. The plants were then rewatered during the subsequent 5 days when the water potential reached about -0.95 MPa. Control plants were, however, kept well hydrated during this period. Starch content decreased during the initial dehydration period, whereas this polymer accumulated immediately after plants were rehydrated. The decrease in starch content was associated with an inhibited branching enzyme activity, while the accumulated starch content was associated with an enhanced enzyme activity. Starch components were purified by use of the Sepharose-2B column chromatography. The average percent beta-amylolysis of amylopectin was higher than the control level (56.1) with the starch content reduced due to dehydration. To the contrary, the value of percent beta-amylolysis with the accumulated starch content was lower than control. These data demonstrate that the fine structure of amylopectin was altered by the modified branchingenzyme activity. The less branched amylopectin structure is compatible with the decrease in starch content and the amltodextrin accumulation. The increased branching in amylopectin is directly related to starch accumulation.



Reprinted from 1986 Proceedings: Beltwide Cotton Production Research Conferences pp. 91 - 92
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998