CO2 ENRICHMENT RESPONSES OF WHEAT - INTERACTIONS WITH TEMPERATURE, NITRATE AND PHOSPHATE

Rising levels of atmospheric CO2, climate change, and fertilizer pollution provide the ecological imperative for investigating the interaction between plant responses to atmospheric CO2 concentration, temperature and nutrient supply. In this study spring wheat (Triticum aestivum L. cv. Wembley) was grown at 40, 50, 60 and 70 Pa atmospheric CO2 pressure and three experiments were conducted to investigate interactions between growth responses to the CO2 treatment and: (i) temperature (24/16 degrees C vs. 18/10 degrees C - day/night), (ii) nutrient solution nitrate concentration (2.5, 5, 10 and 15 mM Ca(NO3)(2).4H(2)O), and (iii) phosphate concentration (0.025 and 0.5 mM KH2PO4). Dry mass and root/shoot ratio increased with CO2 level at the higher temperature. These responses were reversed at the lower temperature. The increase in yield with CO2 enhancement was limited by low rates of nutrient supply in both absolute and relative terms. In the elevated CO2 treatments, the shoot nitrogen concentration was reduced, as was the proportional allocation to the uppermost leaves. These results are discussed with respect to possible physiological mechanisms and potential for improved crop performance in a future, elevated CO2 world.