Nitrogen partitioning in entire plants of different spring wheat cultivars

The aim of this study was to investigate nitrogen partitioning in entire plants, including roots, of spring wheat in two temperature regimes during grain filling. Six cultivars, genetically different and with varying grain protein concentration, were grown in solution culture to full maturity. After anthesis, half the plants were grown in high temperature (23/17 degrees C, day/night) and half in low temperature (18/12 degrees C). Root nitrogen concentration was genetically influenced. The roots had ability to redistribute nitrogen to aboveground plant parts. At maturity the roots contained 10-20 % of the total nitrogen amount in the plants. Harvest index (HI) and harvest index for the entire plant (HItot) for cv. Heta were significantly higher at low temperature than at high. Cv. Heta had a rapid development rate from planting to maturity. Due to slow senescence at low temperature, cv. Karn II showed lower HI and nitrogen harvest index (NHI) at low, compared with high, temperature. Cvs Karn II and Sport showed higher nitrogen amount in the roots and shoots at low, compared with high, temperature. A negative correlation was found between NHI and NHItot vs. root weight, total shoot weight and root N amount. Because of the latter correlation, breeding for low root N concentration is suggested.