Effects of elevated atmospheric CO2 concentrations on the quantitative protein composition of wheat grain

The continuing increase in atmospheric CO2 concentration is predicted to enhance biomass production and to alter biochemical composition of plant tissues. In the present study, winter wheat (Triticurn aestivurn L. cv. 'Batis') was grown under ambient air (BLOW, CO2 concentration: 385 mu L L-1) and free-air CO2 enrichment (FACE, CO2 concentration: 550 mu L L-1) and two different nitrogen (N) fertilization levels (normal N supply: N1 00, 50% of normal N supply: N50). Mature kernels were milled into white flour and analyzed for the contents of crude protein, Osborne fractions, single gluten protein types and glutenin macropolymer. Elevated CO2 caused significant reductions in crude protein and all protein fractions and types (p < 0.001) except albumins and globulins. Effects were more pronounced in wheat samples supplied with normal amounts of N fertilizer. Crude protein was reduced by 14% (N100) and 9% (N50), gliadins by 20% and 13%, glutenins by 15% and 15% and glutenin macropolymer by 19% and 16%, respectively. Within gliadins, omega 5-gliadins (-35/-22%) and omega 1,2-gliadins (-27/-14%) were more affected than a-gliadins (-21/-13%) and alpha-gliadins (-16/-12%). Within glutenins, HMW subunits (-23/-18%) were more affected than LMW subunits (-12/-15%). According to these results, flour from high CO2 grown grain will have a diminished baking quality. To our knowledge, these are the first results of elevated CO2 concentrations impacts on wheat grain protein composition gained under relevant growing conditions at least for Central Europe.