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Plant Physiology 80:812-817 (1986)
© 1986 American Society of Plant Biologists

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Articles

Transport of Gibberellin A1 in Cowpea Membrane Vesicles 1

Sharman D. O'Neill2, Brian Keith and Lawrence Rappaport

Department of Vegetable Crops, University of California, Davis, California 95616, Plant Growth Laboratory, University of California, Davis, California 95616

The permeability properties of gibberellin A1 (GA1) were examined in membrane vesicles isolated from cowpea hypocotyls. The rate of GA1 uptake was progressively greater as pH decreased, indicating that the neutral molecule is more permeable than anionic GA1. Membrane vesicles used in this study possessed a tonoplast-type H+-translocating ATPase as assayed by MgATP-dependent quenching of acridine orange fluorescence and methylamine uptake. However, GA1 uptake was not stimulated by MgATP. At concentrations in excess of 1 micromolar, GA1, GA5, and GA, collapsed both MgATP-generated and artifically imposed pH gradients, apparently by shuttling H+ across the membrane as neutral GA. The relatively high permeability of neutral GA and the potentially detrimental effects of GA in uncoupling pH gradients across intracellular membranes supports the view that GA1 accumulation and compartmentation must occur by conversion of GA1 to more polar metabolites.

2 Present address: Department of Genetics, Briggs Hall, University of California, Davis, CA 95616.

1 Supported by National Science Foundation grant NSF-PCM81-14942.






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ASPB Publications PLANT PHYSIOLOGY THE PLANT CELL
Copyright © 1986 by the American Society of Plant Biologists