Phosphorus Uptake by Six Plant Species as Related to Root Hairs1

Abstract Plant species vary in the amounts of P they obtain from the soil. It was hypothesized that investigation of the differences among species with a mathematical model describing the processes involved in P uptake from soil, would both show why species varied and provide a more rigorous test of a model verified for corn ( Zea mays L.). A controlled climate chamber experiment was conducted with six plant species varying in ability to grow in soils at low levels of soil P. The soil and plant parameters required to operate the model were measured and the agreement between predicted P uptake and observed P uptake evaluated. When the roots were considered to be smooth cylinders absorbing P from soil solution, several species absorbed more P than predicted by the model. The species varied widely in root hair length and density. When the contribution of root hairs to P uptake was included, predicted P uptake agreed with observed uptake. A linear regression gave an r of 0.89 and a slope of 0.89. In addition to root hairs, P uptake efficiency of the plant species was influenced by amount of root surface per gram of plant, rate of plant growth, and the P influx kinetics of the root.