Abstract:  In order to find out the influence of water conditions on the CO2 fertilization，free Air CO2 Enrichment (FACE) system was conducted to research the interaction of the CO2 fertilization and water conditions. Winter wheat was treated with two atmospheric CO2 concentrations: elevated carbon dioxide(550μmol·mol-1) and ambient carbon dioxide(400μmol·mol-1) and two levels of soil moisture: high moisture (75% soil field capacity)and low moisture(55% soil field capacity) to observe the photosynthesis parameter, transpiration, dry matter accumulation and yield components. The results showed that elevated atmospheric CO2 decreased significantly stomatal conductance and transpirationrate, but significantly increased net photosynthetic rate, water use efficiency, yield per plant. The elevated CO2 dramatically benefited for the growth and development of winter wheat and its yield formation. Compared with the high moisture environment, low moisture condition decreased stomatal conductance and transpiration rate,increased net photosynthetic rate, water use efficiency, dry matter accumulation and yield component under elevated CO2.Thus, the elevated CO2 partly reduce the deleterious effects of water stress on the winter wheat. It is much more beneficial for the CO2 fertilization under low moisture environment.

Key words: Elevated CO2, Free Air Carbon dioxide Enrichment (FACE), Soil moisture, Net photosynthetic rate, Water use efficiency