Phosphorus Influx and Growth Characteristics of Corn Roots as Influenced by Phosphorus Supply1

Abstract Knowledge of the effect of P status of corn ( Zea mays L.) plants and P distribution in the toot zone on P influx and root growth is important for simulation modeling of P uptake by corn. Only limited information is available. The objective of this research was to determine the relation between plant P status and the portion of the roots supplied with P on plant P influx and root growth and morphology. Two solution culture experiments were conducted in controlled climate facilities. Phosphorus influx was measured on 18‐day‐old corn plants that had been starved for P for 1 to 6 days. Split‐root experiments were used to measure the effect of P distribution on root growth and P uptake. Starving the plant for P reduced P concentration in the shoot and root and this resulted in a 55% increase in the maximum P influx, Imax. Supplying P to only part of the root system also resulted in a lower plant P concentration and higher Imax by the roots in P solution. When less than 50% of the roots were supplied with P, root growth rate in the P solution was 25% greater than in the minus P solution. Phosphorus uptake was correlated with root surface exposed to P (R 2 = 0.88).