The Absorption and Utilization of Phosphate by Young Barley Plants

Abstract

Organic phosphorus compounds have been extracted from the roots of intact plants which have absorbed radioactive phosphate. The distribution of phosphorus between different organic fractions of the root during a 24-hour absorption period is markedly influenced by the concentration of phosphorus supplied. Less than 1 minute after entry a significant proportion of the absorbed phosphorus is found to be in organic compounds. Incorporation into nucleotides is particularly rapid, whereas incorporation into hexose phosphates occurs more slowly. The pattern of esterification is influenced by the phosphate status of the plants. 2: 4-dinitrophenol (10 ⁻⁴ M.) reduces the uptake of phosphorus and also the extent of esterification, the latter effect being due solely to reduced incorporation into the nucleotide fraction. Although extensive esterification of phosphate occurs in roots, it appears to be transported to the shoot as inorganic phosphate accompanied by only a small amount of a single organic compound.