Calcium Inhibition of Potassium Absorption in Corn Roots

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Abstract
Calcium (or magnesium) sulfate or chloride was found to inhibit energy dependent potassium transport in excised corn roots. This Ca2+ inhibition of K+ transport was most pronounced during the initial phases of transport. As the absorption periods were lengthened the effect of Ca2+ gradually changed from an inhibition to a typical promotion (after about 30-45 min.) of K+ transport. Kinetic analysis indicated the inhibition to be of a non-competitive nature. Identical experiments with excised barley roots showed that CaSO4 had no effect on K+ absorption whereas CaCl2 had a typical stimulatory effect on K+ absorption. Kinetic analysis indicated that both corn and barely have efficient K+ transporting systems but barley roots are approximately 5 times more active (on a fr wt basis) than corn roots. These results illustrate the hazards involved in applying results obtained with 1 (or even several) plant species to all species.
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