Efficiency and kinetics of phosphorus uptake from soil by various barley genotypes

Summary

Barley cultivars grown under field conditions of moderate deficiency of phosphorus (P) had great differences in P uptake and grain yields.

As the rate determining step in P uptake under these conditions is located in the root net influx of P (Ī_nL*) per g of dry matter of the plant can be expressed by

$$ \bar I_n L* = \bar I_{max} L*\frac{{c - c_{min} }} {{c - c_{min} + K_m }} $$

where Ī_n, L*, Ī_max, c, c_min and K_m denote mean net influx per unit length of the root, root length per unit weight of the plant, maximal mean net influx per unit length of the root, P concentration at the root surface, minimum concentration in solution of which net influx appears to be zero and Michaelis-Menten factor of P uptake, respectively. Studies of P uptake kinetics in water culture showed that the values of L*, Ī_max, K_m and c_min of P uptake varied considerably between barley cultivars. Furthermore, agreement was found between P uptake in the field and P uptake predicted from Ī_max-, K_m-, c_min- and L*-values observed in water culture experiments.

The data thus indicate that it should be possible to improve the efficiency by which plants utilize soil as a source of P by selecting and/or developing genotypes of barley with a smaller c_min and/or K_m and a greater Ī_max and/or L* during the main period of growth.

The results suggest therefore that it should be feasible to adapt plants to a considerably lower soil P level.