Calculation of Rate of Nutrient Uptake by Growing Roots1

Abstract

AbstractEquations are presently available to calculate the rate of nutrient uptake by growing roots. They can be used to estimate an average rate of uptake by the entire root system, but they fail to give specific information on uptake by a unit segment of root or on the effects of aging and morphological changes of such a segment on its capacity for uptake. This paper gives a theoretical analysis of the process of nutrient uptake by a growing root system. The objective of this analysis is to derive equations that would give such specific information. A frequency distribution function is used to partition root systems into a continuum of age groups, each possessing a rate of uptake that is a function of the age of that group. Equations are derived that utilize time‐series measurements of root length and nutrient accumulation in the plant. These derivations are used to calculate parameters of nutrient uptake related to two properties of the root system: (i) the rate of nutrient uptake of a unit segment of root and the manner by which this rate changes with aging and (ii) the rate of nutrient flux into the entire root system as a function of time.