Control of sucrose concentration in sorghum stem after grain maturity /
| Main Author: | |
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| Other Authors: | , , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Knowledge of mechanisms regulating differential sucrose accumulation in stems of diverse sorghum [Sorghum bicolor (L.) Moench] types after grain physiological maturity would reveal opportunities for genetic manipulation to enhance biomass yield as a byproduct of grain production. Possible mechanisms studied were i) modulation of carbon exchange rate and leaf export through shifts in assimilate allocation among leaf carbohydrates, and ii) stem-situated controls through assimilate metabolism and assimilate compartmentation. A method was first established for estimating assimilate allocation at particular growth stages in numerous samples. The method used hexokinase to convert [14C]hexose to hexose-phosphate, which was then reproducibly (SE = 1.3%) separated (> 95%) from [14C] sucrose by batch treatment with anion exchange resin. The method was applied in examining the first possible mechanism. Of the possible mechanisms studied, two appear to be relatively unimportant: i) modulation of leaf export through allocation among leaf carbohydrates and ii) control through stem assimilate metabolism. Although diurnal and hybrid differences in [14C] assimilate allocation among leaf sucrose, hexose, and starch were demonstrated, these differences were small compared to diurnal and hybrid variation in leaf export of [14C] assimilate during 4 h of daylight. A survey of extractable stem activities of soluble sucrose-degrading enzymes in diverse genotypes showed activities were low prior to sucrose accumulation, and could not have controlled differential sucrose accumulation. These studies did speculate a role for leaf compartmentation of sucrose, and suggest sucrose inversion in panicle during grain filling, and suggest pretranslational, thus nonartifactual, regulation of stem Sus2 sucrose synthase activity during sucrose accumulation. To understand the role of the third possible mechanism, a novel application of stem infusion was evaluated. Infusion of [14C] sucrose left local sucrose concentration unaltered, but created downward gradients in stem of intracellular 80% ethanol soluble and insoluble [14C] components... |
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| Item Description: | Vita. "Major subject: Plant Physiology." |
| Physical Description: | xii, 100 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |