Abstract
Evidence is presented that K+ uptake in corn root segments is coupled to an electrogenic H+/K+ -exchanging plasmalemma ATPase while phosphate uptake is coupled to an OH−/Pi antiporter. The plasmalemma ATPase inhibitor, diethylstilbestrol, or the stimulator, fusicoccin, altered K+ uptake directly and phosphate uptake indirectly. On the other hand, mersalyl, an OH−/Pi antiporter inhibitor, inhibited phosphate uptake instantly but only slightly affected K+ uptake. Collapse of the proton gradient across the membrane by (p-trifluoromethoxy) carbonyl cyanide phenylhydrazone resulted in immediate inhibition of K+ uptake but only later inhibited phosphate uptake. Changing the pH of the absorption solution had opposite effects on K+ and phosphate uptake. In addition, a 4-hour washing of corn root tissue induced a 5-fold increase in the rate of K+ uptake with little or no lag, but only a 2- to 3-fold increase in phosphate uptake with a 30- to 45-minute lag. Collectively these differences strongly support the coupling of an electrogenic H+/K+ -exchanging ATPase to an OH−/Pi antiporter in corn root tissue.
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Selected References
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