A method for determining Michaelis‐Menten kinetic parameters of nutrient uptake for plants growing in soil

Abstract

The relationship between nutrient influx (In) and solution concentration at the root surface (Clo) has not yet been determined for roots growing in soil because of difficulties in measuring Clo. Corn was grown on two soils with 12 and 21% clay. Each soil had five K levels ranging from low to very high. Potassium influx (In) was determined from K uptake between two harvests and root length. Clo was then calculated from the average soil solution concentration and In by assuming that diffusion is the main transport mechanism for K to the root. Potassium influx plotted against Clo showed a saturation curve, typical of a Michaelis‐Menten kinetic relationship. The Michaelis‐Menten uptake parameters, maximum influx (Imax) and Michaelis constant (Km), were obtained by the “Hanes” plot. There was close agreement, without lack of fit, between calculated and observed data. The proposed procedure therefore appears to be suitable for estimating the uptake kinetics of roots growing in soil. Requirements for applications of the method are discussed.

Mechanistic simulation models of nutrient uptake: A review

“…More recently, Baldwin et al (1973), Brewster et al (1976, Claassen andBarber (1976), Cushman (1979), Barber and Cushman (1981), Itoh and Barber (1983a), Claassen et al (1986), Hoffland et al (1990a), and Hoffland (1992 have combined the theoretical model of nutrient uptake for a single root with the rate of root growth to predict total nutrient uptake over a period of time. For such a calculation, initial root length together with the growth-rate constant (rate of change in root length as a function of time), root density in a finite soil volume (half-distance between root axes), and the mean root radius may suffice (Barber, 1984;Barber and Cushman, 1981).…”

“…Another way to estimate Michaelis-Menten kinetic parameters of nutrient uptake for plants growing in soil is to calculate average nutrient influx from the data on nutrient uptake and root length for two harvests (Seeling and Claassen, 1990). Nutrient concentration at the root surface can then be calculated from bulk soil solution concentration and average nutrient influx taking into account the ways of nutrient transport toward sorbing root surface (diffusion only in the case of K, Seeling and Claassen, 1990).…”

“…Nutrient concentration at the root surface can then be calculated from bulk soil solution concentration and average nutrient influx taking into account the ways of nutrient transport toward sorbing root surface (diffusion only in the case of K, Seeling and Claassen, 1990).…”

“…Similarly, differences due to nutritional status of plants are generally neglected. Since plants grown in nutrient solution and soil would certainly have different nutrient status, determination of Michaelis-Menten kinetic parameters for plants growing in soil (Seeling and Claassen, 1990) appears to be the method that would partly overcome this problem. However, generalisation over various soil types would still not be possible because plants grown in different soils, or in the same soil with different fertilisation, watering, etc., would have different nutrient status.…”

Mechanistic numerical modeling of solute uptake by plant roots

“…at very low concentration levels that may be hard to be accurately measured. Seeling and Claassen (1990) show that C min can be neglected for the cases of high K m values.…”