Solubilization of rock phosphate by rape

Abstract

Local rhizosphere acidification by rape as a reaction to P-starvation was visualized by means of an agar plate technique. By means of a modification of this technique local differences in cation-anion uptake and organic acid exudation along intact roots of rape were observed for plants grown on nutrient solution with or without added P. No differences in uptake rates of K-, NO3- and Ca-ions could be detected between P-starved and P-supplied plants. However, exudation of malic and citric acid was distinctly higher in acidified root zones of P-starved plants, coinciding with higher levels of malate in the corresponding root tissue. Organic acid exudation is indicates as the cause of local rhizosphere acidification by rape as a reaction to P-starvation and as a possible mechanism of its phosphate-solubilizing capacity.