Glucose-6-phosphate Dehydrogenase Activity under Conditions of Water Limitation: a Possible Model System for Enzyme Reactions in Unimbibed Resting Seeds and its Relevance to Seed Viability |
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Authors: | STEVENS, EVELYN STEVENS, L. |
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Abstract: | A model system has been used to measure glucose-6-phosphatedehydrogenase (G-6-PDH) activity when the water contents ofthe reactants are comparable to the water contents of dry restingseeds. The activity of G-6-PDH is reduced by 102103 whenthe water content is limited to between 1.5 and 25 per cent.G-6-PDH activity is affected by temperature and by the proteincontent of the model system. The glucose 6-phosphate (7.03 nmolg1 embryo) and the NADP+ (25.0 nmol g1 embryo)contents of barley embryos were measured. Using these measurements,together with the measurements in the model system of G-6-PDHactivity at low water concentrations, an estimate is made ofthe G-6-PDH activity in resting barley embryo. A cor-relationbetween estimated G-6-PDH activity at different water contentsand the periods for which seeds remain viable is indicated.The limitations of the model system are discussed. |
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