Abstract: 【Objective】This study aims to elucidate the interactive effects of elevated CO₂ concentration [CO₂] and different nitrogen applications on phenology, photosynthesis and yield of winter wheat, then to provide theoretical understanding for objective assessment on the potential yield of winter wheat under climate change conditions.【Method】The experiment was conducted from 2011-2014 using a Free Air CO₂ Enrichment (FACE) facility with pot experiment and winter wheat cultivar “Zhongmai 175”. Each pot was filled with 45 kg of sieved soil. The treatments were set at elevated [CO₂] of 550 mg·L^-1 and ambient [CO₂] of 390 mg·L^-1，nitrogen fertilizer applied at N1, 0.16g·kg^-1 soil and N0, 0 g·kg^-1 soil. The changes of phenology, physiology and yield of winter wheat were investigated. The elevated CO₂ feeding was in operation from regreen to maturity stage each year and injected time from 6:30-18:30 each day, and no CO₂ was released at night. The [CO₂] was controlled through computer program and could synchronously adjust with wind speed and direction time by a solenoid valve in a release pipe, then it achieved the expected [CO₂].【Result】The pot experiment results indicated that elevated [CO₂] accelerated the growth process of winter wheat compared with ambient [CO₂], jointing stage speeded up of 1 day, flowering period can be 1-2 days in advance, and the whole growth duration was shortened 3-5 days under the same fertilizer level. While as the high nitrogen could prolong the growth duration, the flowering period can be extended by 1-2 days, filling period by 4-5 days, synchronous alleviated the accelerative effects of elevated [CO₂] on growth process; High [CO₂] enhanced winter wheat yield about 16.0% via increased grain number per spike and grains weight significantly, and photosynthesis of flag leaves was enhanced by 13.7% compared with ambient [CO₂]. Under elevated [CO₂] conditions, higher application of nitrogen fertilizer could increase the yield of winter wheat about 50%，enhance the photosynthesis increase rate about 2.5% and transpiration about 13.5% compared with low nitrogen fertilizer supply. That means the nitrogen fertilization can not only promote the high [CO₂] positive effect, but still plays a more important role to maintain a stable and higher yield of winter wheat even with [CO₂] enrichment conditions; Moreover, elevated [CO₂] can increase the grain number per spike by 3.69% compared with ambient [CO₂], higher nitrogen increased by 3.43% compared with low nitrogen, the dual role of high nitrogen and high [CO₂] increase grain number highest of 38.37 grains/ear, low nitrogen and ambient [CO₂] treatment had the lowest level of spike grain numbers, which indicated high [CO₂] has the slightly higher positive effects than that of a purely nitrogen treatment on grain number. Dual effects of high [CO₂] and nitrogen had the most positive effects on grain number, but the effects had no obvious difference if these measures are used separately. High [CO₂] increased grain weight by 5.3%, and if it combined with high nitrogen that the grain weight could increase 7.3%. All these showed that nitrogen promoted the positive effects of high [CO₂] on grain weight.【Conclusion】Therefore, under future climate change conditions, higher [CO₂] has positive effects to enhance yield of winter wheat and has obvious positive interactions with nitrogen, high nitrogen can extend the growth period which mitigate the shorten growth duration by higher [CO₂], improve photosynthesis and promote CO₂ fertilization effects. Higher [CO₂] could increase yield via high grain number per spike and grains weight which could be considered for wheat breeding.

Key words: winter wheat, FACE, CO₂, nitrogen, yield