The effect of phosphate deficiency on the kinetics of phosphate absorption by sterile excised barley roots, and some factors affecting the ion uptake efficiency of roots

Abstract

Abstract The influence of phosphate nutrition on the kinetics of phosphate absorption by sterile excised barley roots was examined. The roots of seedlings grown in dilute CaSO4 showed uptake kinetics similar to roots grown in phosphate deficient nutrient culture. The absence of microorganisms did not abolish the dual form of the absorption isotherm at pH 4.0 The most important effect of phosphate deficiency for uptake at low phosphate concentration was a marked decrease in the apparent dissociation constant of the ion‐carrier complex postulated to be involved in the uptake process. The results are discussed in relation to kinetic factors which may influence the efficiency of ion uptake by roots of different species of plants, including the apparent dissociation constant, the rate constant for uptake and the concentration of the ion‐carrier system.