A ROLE FOR THE AKT1 POTASSIUM CHANNEL IN PLANT NUTRITION

In plants, potassium serves an essential role as an osmoticum and char ge carrier. Its uptake by roots occurs by poorly defined mechanisms. T o determine the role of potassium channels in planta, we performed a r everse genetic screen and identified an Arabidopsis thaliana mutant in which the AKT1 channel gene was disrupted. Roots of this mutant lacke d inward-rectifying potassium channels and displayed reduced potassium (rubidium-86) uptake. Compared with wild type, mutant plants grew poo rly on media with a potassium concentration of 100 micromolar or less. These results and membrane potential measurements suggest that the AK T1 channel mediates potassium uptake from solutions that contain as li ttle as 10 micromolar potassium.