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 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 mins) 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 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.