The Uptake and Utilization of Phosphorus and Nitrogen by Diploid, Tetraploid and Hexaploid Wheats (Triticum spp.)

Abstract

Twenty genotypes of Triticum and Aegilops wheats including diploid, tetraploid and hexaploid types, were grown under contrasting phosphorus (P) regimes (control and low P) at 15 °C by day and 10 °C at night. Dry-matter production and phosphorus and nitrogen uptake and distribution were measured on mature plants. Phosphorus efficiency (PE) was considered in terms of yield per unit of P in the main shoot and concentration of phosphorus in grain (per cent P). In the low-P set, PE, which ranged from 110 to 715 mg grain mg−1 P, increased as the yield per culm and dry-matter partitioning (harvest index) increased, with hexaploid > tetraploid > diploid. In both the control and low-P plants percentage P in grain decreased in the order diploids > tetraploids > hexaploid wheats. Grain phosphorus was highly negatively correlated with the log of grain yield (r = −0.74; −0.88) and the log of harvest index (r = −0.80 and −0.88) for control and low-P plants, respectively. This suggests that future gains in plant harvest index will cause smaller reductions in grain phosphorus concentrations. But, within either a high or low phosphorus supply, wheats with a given grain harvest index have significantly different grain phosphorus concentrations, and conscious selection for this character is feasible. Low-P plants had similar grain nitrogen concentrations but lower nitrogen harvest indexes than control plants.