High phosphorus supply reduced zinc concentration of wheat in native soil but not in autoclaved soil or nutrient solution

Phosphorus (P)-induced zinc (Zn) deficiency is one of the most commonly studied antagonistic interactions in plant nutrition. However, there are many controversial reports about P-Zn interaction, possibly related to growth conditions. In this study, the effects of P supply on the root uptake and tissue concentrations of Zn as well as the development of Zn deficiency were investigated in wheat (Triticum aestivum) grown in different media. Plants were grown under greenhouse and growth chamber conditions in native soil, autoclaved soil and nutrient solution with different P and Zn supplies. In the soil experiment, the shoot biomass and grain yield were measured whereas in the nutrient solution experiment, the root and shoot biomass were determined. Development of Zn deficiency symptoms was examined. Concentrations of Zn, P and other elements were measured in harvested tissues. Mycorrhizal colonization of roots was scored in soil-grown plants. Root uptake of stable Zn isotope (Zn-70) was investigated at different P rates in a separate nutrient solution experiment. Higher P rates caused substantial decreases in shoot and grain Zn concentrations in native soil but not in autoclaved soil. Treatment of native soil with increasing P significantly reduced mycorrhizal colonization. At low Zn, P applications aggravated Zn deficiency symptoms in both soil and solution culture. In solution culture, root and shoot Zn concentrations were not lowered by higher P rates. Root uptake of Zn-70 from nutrient solution was even depressed at low P. The negative effect of increasing P supply on root Zn uptake and tissue Zn concentrations in wheat is mycorrhiza-dependent and may completely disappear in a mycorrhiza-free environment.