Can elevated CO 2 combined with high temperature ameliorate the effect of terminal drought in wheat?

Wheat (Triticum aestivum L.) production may be affected by the future climate, but the impact of the combined increases in atmospheric CO [sub 2] concentration, temperature and incidence of drought that are predicted has not been evaluated. The combined effect of elevated CO [sub 2], high temperature and terminal drought on biomass accumulation and grain yield was evaluated in vigorous (38-19) and nonvigorous (Janz) wheat genotypes grown under elevated CO [sub 2] (700 μL L-1) combined with temperatures 2°C, 4°C and 6°C above the current ambient temperature. Terminal drought was induced in all combinations at anthesis in a split-plot design to test whether the effect of elevated CO [sub 2] combined with high temperature ameliorates the negative effects of terminal drought on biomass accumulation and grain yield. Biomass and grain yield were enhanced under elevated CO [sub 2] with 2°C above the ambient temperature, regardless of the watering regimen. The combinations of elevated CO [sub 2] plus 4°C or 6°C above the ambient temperature did not enhance biomass and grain yield, but tended to decrease them. The reductions in biomass and grain yield (45-50%) caused by terminal drought were less severe (21-28%) under elevated CO [sub 2] with 2°C above the ambient temperature. The amelioration resulted from a 63% increase in the rate of leaf net photosynthesis in 38-19 and a 39% increase in tillering and leaf area in Janz. The contrasting responses and phenological development of these two genotypes to the combination of elevated CO [sub 2], temperature and terminal drought, and the possible influences on their source-sink relationships are discussed. Wheat may have different responses to future climates in Australia. Grain yield and biomass under elevated CO [sub 2] increased when the temperature was 2°C higher than the ambient, regardless of irrigation or terminal drought, but not when temperatures were >2°C higher than the ambient. The interaction of elevated CO [sub 2] × temperature × drought should be considered in the new generation of studies on crop adaptation to future climates in Australia. [ABSTRACT FROM AUTHOR]