Phosphate absorption by intact rice plants was found to be mediated by two distinct mechanisms when studied over a range of phosphate concentrations from 0.16 to 161µM . A low concentration, high affinity (Km = 1.4 x 10-6M) mechanism becoming saturated at about 2.5 x 10-6M phosphate, and a low affinity (Km = 7 x 10-6M) mechanism operative at higher phosphate concentrations were observed. The role of both mechanisms in phosphate absorption by plants growing in the soil is discussed.