Fluxes of H+ and K+ in Corn Roots
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Discussion
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Implication
Electrophysiological study reveals coupled potassium and proton fluxes in corn seedling roots, suggesting potassium uptake occurs via cotransport rather than an antiporter.
Key Points
- Quantify simultaneous electrochemical potential gradients and fluxes of H+ and K+ at the root surface of corn seedlings to determine the mechanism of potassium uptake.
- Measured steady-state electrochemical potential gradients for H+ and K+ in the unstirred layer of 4-day-old intact corn seedlings and root segments using ion-selective microelectrodes.
- Compared microelectrode-derived net K+ influx with unidirectional K+ (86Rb+) influx kinetic data across varying K+ concentrations.
- Concurrently monitored cortical membrane potential and net K+ influx across the micromolar K+ concentration range.
- Calculated H+:K+ stoichiometry was highly variable, showing that net K+ influx was rarely charge-balanced by net H+ efflux.
- Cortical membrane potentials exhibited high sensitivity to micromolar K+, with depolarization Michaelis constants (Km 6–9 µM K+) closely aligning with net K+ influx kinetics (Km 4–7 µM K+).
Cite This Study
Newman et al. (1987) studied this question.