CHANGES IN WHEAT-GRAIN QUALITY DUE TO DOUBLING THE LEVEL OF ATMOSPHERIC CO2

Elevated levels of atmospheric CO2 have been shown to increase grain y ield and reduce grain nitrogen concentration. The object of this study was to determine whether elevated CO2 levels would modify other aspec ts of grain quality relevant to processing, particularly protein and s tarch quality. Wheat of two genotypes (Hartog and Late Hartog) was gro wn in the field in controlled-atmosphere tunnels at either the ambient level of CO2 (350 mu l/L) or an elevated level (700 mu l/L). This ele vated level of CO2 produced significant increases in grain yield, but decreases in 1,000-kernel weight. Grain grown in the elevated CO2 atmo sphere produced poorer dough and decreased loaf volume, farinograph de velopment time, and dough extensibility. These changes were largely at tributable to the lower protein content of the grain grown at elevated CO2. There did not appear to be major changes in protein composition or in the functional properties of the protein. Grain produced at elev ated CO2 yielded starch with a significantly higher proportion of larg e (A-type) starch granules but no overall change in amylose-to-amylope ctin ratio. These studies indicate that elevated levels of CO2 may res ult in decreased quality of bread wheats largely due to lowered protei n content.