Zinc (Zn)-phosphorus (P) interactions in two cultivars of spring wheat (Triticum aestivum L.) differing in P uptake efficiency

Zinc-phosphorus (Zn-P) interactions were investigated in two wheat cultivars (Brockton and Krichauff) differing in P uptake efficiency, The experiment was carried out in a growth chamber. Rock phosphate or CaHPO4 were used as P sources, and ammonium nitrate or nitrate only as nitrogen sources. Two Zn levels were used: 0.22 and 2.2 mg ZnSO4. 5H(2)O kg(-1). The results confirmed that Brookton had a higher P uptake efficiency than Krichauff under low P conditions, irrespective of nitrogen and Zn supply. Zn supply had little effect on tissue P concentration and P uptake per unit of root weight in either cultivar, irrespective of nitrogen supply. An increase in P availability caused a significant reduction in Zn uptake per unit of root weight, and tissue concentration of Zn in both cultivars. The reduction in tissue Zn concentration cannot be explained entirely by a dilution effect. Zn uptake by, and Zn concentrations in, Brockton (with high P uptake efficiency) were significantly lower than those of Krichauff. Zn concentrations in Brockton were more sensitive to P uptake than those in Krichauff. It is suggested that high P uptake efficiency may depress plant uptake of Zn, and therefore cause a reduction in the concentration (density) of Zn in grains of wheats grown in low P (and possibly tow Zn) soils. (C) 2001 Annals of Botany Company.