Wheat grain quality under increasing atmospheric CO2 concentrations in a semi-arid cropping system

We investigated wheat (Triticum aestivum) grain quality under Free Air CO ₂ Enrichment (FACE) of 550 ± 10% CO ₂ μmol mol ^-1. In each of two full growing seasons (2008 and 2009), two times of sowing were compared, with late sowing designed to mimic high temperature during grain filling. Grain samples were subjected to a range of physical, nutritional and rheological quality assessments. Elevated CO ₂ increased thousand grain weight (8%) and grain diameter (5%). Flour protein concentration was reduced by 11% at e[CO ₂], with the highest reduction being observed at the late time of sowing in 2009, (15%). Most of the grain mineral concentrations decreased under e[CO ₂] - Ca (11%), Mg (7%), P (11%) and S (7%), Fe (10%), Zn (17%), Na (19%), while total uptake of these nutrients per unit ground area increased. Rheological properties of the flour were altered by e[CO ₂] and bread volume reduced by 7%. Phytate concentration in grains tended to decrease (17%) at e[CO ₂] while grain fructan concentration remained unchanged. The data suggest that rising atmospheric [CO ₂] will reduce the nutritional and rheological quality of wheat grain, but at high temperature, e[CO ₂] effects may be moderated. Reduced phytate concentrations at e[CO ₂] may improve bioavailability of Fe and Zn in wheat grain.