Interactions Between Intact Barley Plants . Potassium and Calcium in Their Absorption by I . Effects of Potassium on Calcium Absorption '

A bstract. Increasing concentrations of K (20, 200, 2000 ,uM) in the nutrient solution depressed Ca content and concentration in barley plants growing in nutrient solutions of low Ca concentrations (250 and 2500 Mm). Increasing K from 20 to 200 AM depressed Ca absorption more than increasing K from 200 to 2000 FM K. The strong depression of Ca absorption by low concentraltions of K must involve a different process from that studied by other workers at high concentrations of K. Since the depression in net absorption of Ca was as great at 250 as at 2500 aM Ca the results fail to support previous suggestions that a specific mechanism for Ca absorption operates at low Ca concentrations. It is suggested that, at the low concentrations of K and Ca likely to be found at the root surface in many sioil solutions, the above mentioned effect of K in inhibiting Ca obsorption may be important in the Ca nutrition of plants.