Kinetics of P Absorption by Excised Roots and Leaves of Corn Hybrids1

Abstract

AbstractThe kinetics of phosphate uptake was studied using H332PO4 to determine if the observed differences in accumulation of inorganic phosphate by corn hybrids could be explained on the basis of genetic differences in the mechanism of absorption. The absorption of phosphate by corn roots was found to be similar to that for barley roots in that two independent mechanisms of ion absorption were observed. Vmax for the absorption at high concentration was 40 × 10−8 mole P/Mg root × hour, while that of the low concentration reaction was 1× 10−8 mole P/Mg root × hour. The Km for the high and low concentration reactions were 2 × 10−1 and 10−4 mole P/liter, respectively.No difference was observed in the kinetics of uptake of phosphate by roots of the corn hybrids studied. Phosphate absorption by excised leaves was found to be different for the high and low phosphorus accumulators. The difference in absorption rates suggests a difference between hybrids in the strength of the phosphorus‐carrier bond. The variation observed between hybrids was sufficient to account for a 1.6‐fold difference in accumulation of phosphate.