Concentration of citric and malic acids in root exudates of P-deficient or P-sufficient plant species. Wheat, tomatoe and chickpea initially received 0.25 mm P, and root exudates collected following a period of P deprivation. For these three species, 0.0 acid concentration ranges from actual zero to negative values relative to the control. Values followed by different letters for P treatments of each plant species are significant different at P < 0.05. The other values had standard deviations ranging from 0 to 25%