Abstract
Rye (Secale cereale cv. Rheidol) and wheat (Triticum aestivum cv. Mardler) were grown at shoot/root temperatures of 20/20 °C (warm grown, WG plants), 8/8 °C (cold grown, CG plants) and 20/8 °C (differential grown, DG plants). Plants from contrasting growth temperature regimes were standardized and compared using a developmental timescale based on accumulated thermal time (°C d) at the shoot meristem. Accumulation of dry matter, nitrogen and potassium were exponential over the time period studied (150–550 °C d). In rye, the rates of plant dry matter and f. wt accumulation were linearly related to the temperature of the shoot meristem. However, in wheat, although the rates of plant dry matter and f. wt accumulation were temperature dependent, the linear relationship with shoot meristem temperature was weaker than in rye. The shoot/root ratio of rye was stable irrespective of growth temperature treatment, but the shoot/root ratio of wheat varied with growth temperature treatment. The shoot/root ratio of DG wheat was 50% greater than WG wheat. In both cereals, nutrient concentrations and dry matter content tended to be greater in organs exposed directly to low temperatures. The mean specific absorption rates of nutrients were calculated for the whole period studied for each species/temperature combination and were positively correlated with both plant shoot/root ratio and relative growth rate. The data suggest that nutrient uptake rates were influenced primarily by plant demand, with no indication of specific nutrient limitations at low temperatures.