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Cessation of Assimilate Uptake in Maturing Soybean Seeds

Charles D. VerNooy, John H. Thorne, Willy Lin and Ross M. Rainbird
Plant Physiology
Vol. 82, No. 1 (Sep., 1986), pp. 222-225
Stable URL: http://www.jstor.org/stable/4270161
Page Count: 4
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Cessation of Assimilate Uptake in Maturing Soybean Seeds
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Abstract

In vitro assimilate uptake and metabolism were evaluated in embryos of known age isolated from seeds at mid-podfilling through physiological maturity. The capacity of isolated Wye soybean embryos to take up exogenous [14C]sucrose dropped nearly 4-fold in less than 1 week at incipient cotyledon yellowing. This drop in rate of sucrose uptake coincided with cessation of seed growth as well as rapid decline in leaf photosynthetic rate that preceded leaf yellowing. Conversely, the rate of [3H]glutamine uptake by cotyledons increased as they yellowed. Yellow cotyledons also rapidly converted exogenous [3H]glutamine to ethanol-insoluble components, but converted little exogenous [14C]sucrose to ethanol-insoluble components, primarily because of greatly reduced sucrose uptake. Sustained import and metabolism of amino acids remobilized from senescing leaves may prolong seed growth beyond loss of photosynthetic competency and sucrose availability.

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