首页 | 本学科首页   官方微博 | 高级检索  
   检索      


H and k electrogenic exchanges in corn roots
Authors:Thibaud J B  Soler A  Grignon C
Institution:Biochimie et Physiologie Végétales, Institut National de la Recherche Agronomique (Centre National de la Recherche Scientifique, UA 573), Ecole Nationale Supérieure Agronomique, 34060 Montpellier Cedex, France.
Abstract:The membrane potential difference, the net H+ exchange rate, the K+ net flux, and the K+ (86Rb+) influx were measured in excised corn roots as functions of the K+ concentration in the medium at various pH values, in the presence of poorly permeant anions. The roots behaved as a K+/H+ exchange system. By comparing the results in normal or hypoxic conditions, or in the presence of vanadate, it was possible to distinguish the active components of membrane potential and transports from the passive ones. The magnitude of the electrogenic potential was not related to the active H+ extrusion rate. At pH 6, the variations of the electrogenic potential resulted from variations of the stoichiometry of the active H+/K+ exchange. The same relationship between this stoichiometry and the K+ concentration was observed in conditions ensuring different membrane polarizations (pH 6, pH 4, or pH 6 with fusicoccin). Both metabolic and Mg-ATPase specific inhibitors stopped the active H+ transport and the net K+ influx. Nevertheless, the tracer influx in the presence of vanadate remained higher than the passive influx calculated from the permeability coefficient determined in hypoxia. It is proposed that vanadate uncouples the K+ moiety of the H+/K+ antiport and allows it to mediate isotopic exchanges.
Keywords:
本文献已被 PubMed 等数据库收录!
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号