[Effects of free-air CO2 enrichment (FACE) on dry matter production and allocation in wheat].

A free-air CO2 enrichment (FACE) experiment was conducted in 2001-2003 to study the effects of predicted higher CO2 levels on the dry matter (DM) production and allocation in winter wheat variety Ningmai 9. The results showed that under FACE, the DM production had an increase of 10. 8% , 31. 6% , 40. 5% and 27. 2% during the growth periods from sowing to wintering ( Period 1 ) , wintering to jointing ( Period 2) , jointing to booting ( Period 3) , and booting to heading (Period 4) , respectively, but a decrease of 5. 5% in the period from heading to grain maturity (Period 5). As a result, the final total biomass at maturity was increased by 13. 6%. FACE had no significant effect on leaf area index (LAI) and net assimilation rate (NAR) in Period 1, but made the LAI in Period 2 increased obviously, and the NAR decreased dramatically in Period 3. Under FACE, the proportion of leaf to total above-ground DM decreased, while that of stem (including sheath) to total above-ground DM showed an opposite trend in the whole growth period. The percentage and total amount of soluble sugar and starch in the stem at grain-filling stage were also increased obviously under FACE.