Calcium Inhibition of Potassium Absorption in Corn Roots

Calcium (or magnesium) sulfate or chloride was found to inhibit energy dependent potassium transport in excised corn roots. This Ca(2+) inhibition of K(+) transport was most pronounced during the initial phases of transport. As the absorption periods were lengthened the effect of Ca(2+) gradually changed from an inhibition to a typical promotion (after about 30-45 mins) of K(+) transport. Kinetic analysis indicated the inhibition to be of a non-competitive nature.Identical experiments with excised barley roots showed that CaSO(4) had no effect on K(+) absorption whereas CaCl(2) had a typical stimulatory effect on K(+) absorption. Kinetic analysis indicated that both corn and barley 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.