Energetics of sucrose transport into protoplasts from developing soybean cotyledons |
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Authors: | Lin W |
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Affiliation: | Central Research and Development Department, E. I. du Pont de Nemours and Company, Experimental Station, Wilmington, Delaware 19898. |
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Abstract: | The accumulation of tetraphenylphosphonium (TPP+), 5,5′-dimethyl-oxazolidine-2,4-dione (DMO), and a micro pH electrode were used to measure membrane potential, intracellular and extracellular pH, respectively, upon the addition of exogenous sucrose to soybean cotyledon protoplasts. Addition of sucrose caused a specific and transient (a) depolarization of the membrane potential (measured by TPP+ accumulation), (b) acidification of the intracellular pH (measured by DMO accumulation), and (c) alkalization of the external medium (measured by a micro pH electrode). The time course for all these changes was similar (i.e. 5 to 10 minutes). Based on the rate of sucrose uptake and alkalization of the external medium, a stoichiometry of 1.02 to 1.10 for proton to sucrose was estimated. These data strongly support a proton/sucrose cotransporting mechanism in soybean cotyledon cells. |
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