| Winter wheat is a very important grain crop in China. Climate chamge is happening with elevated CO2, how yield of winter wheat response to elevated CO2, and how elevated CO2 influnce on winter wheat growth,development and nitrogen uptake are becoming an urgent scientific question to answer. Experiment were based on the CAAS's FACE system, with two CO2 concentration levels (550±60 ppm and 400±40 ppm),two N fertilizer leavl (Normal Nitrogen is 189kg·hm-2 and Low Nitrogen is 47kg·hm-2) and two winter wheat varieties( CA0493 and ZM175). Each treatment has three replicants.Experimets were taken to investigate the response of wheat growth to elevated CO2 at Changping, Beijing. Research was done on effects of elevated CO2 on the morphology, yield, dry matter production and distribution, nitrogen uptake and utilization and photosynthetic acclimation. Conclusions are listed as follows:(1) Elevated CO2 resulted in taller wheat (+2.78%) and larger flag leaf area (+8.98%).That is interesting to find that with LN conditions, stimulation of flag leaf area with elevated CO2 was greater than NN conditions.we conculd that flag leaf area increased, but became thinner at elevated CO2.(2) Effect of elevated CO2 on yield was different between two varieties.Yield of CA0493 increased 24.67% significantly with exposure to elevated CO2; however, yield of ZM175 showed litter effect of elevated CO2.Leaf sencense got earier for wheat of ZM175 with exposure to elevated CO2, which will limit the response of ZM175 to elevated CO2 and result in difference of yield response to elevated CO2 between two varieties.For CA0493, elevated CO2 increased the kernel number per spike up to 3.45 kernels per spike, that is 14.48% increasment(P=0.059), which was the main reason for CA0493 to increase yield.(3) The interaction effects of CO2×N×variey on aboveground dry matter was significant. For CA0493 exposed to elevated CO2, normal nitrogen fertilizer did stimulate aboveground dry matter, however, for ZM175 exposed to elevted CO2, aboveground dry matter increased with Low nitrogen.(4) At the later stage of CA0493, elevated CO2 decreased the proportion of leaf dry matter to aboveground dry matter and stem dry matter propotion, but increased the head dry matter proportion.That is good for head of CA0493 to get more dry matter. At the later stage of ZM175, elevated CO2 devreased the proportion of leaf dry matter to aboveground dry matter, but increased stem drymatter proportion and head dry matter proportion.(5) Aboveground N uptake increased 9.78% with exposure to elevated CO2(P=0.098) at dough maturity. More nitrogen was shifted to stem and head at elevated CO2 and leaves were main source of nitrogen at flowering stage. While till dough maturiety, leaf and stem were main source of nitrogen and shifted more nitrogen to head at elevated CO2.(6) For ZM175, elevated CO2 resulted in higher Pn(+32.36%～+38.35%) before flowering, however, decreased in dough maturity. Stomal conductance decreased (-25.78%～-87.08%) significantly afer flowering with exposure to elevated CO2. Transporation rate decreased at elevated CO2, but Ci/Ca increased 10.67% in booting and 32.35% in dough maturity at elevated CO2, respectively.(7) In dough maturity, photosynthetic acclimation occurs in the flag leaf of ZM175. Elevated CO2 decreased the content of chlorophyll and SPAD in dough, which means that leaf of ZM175 got earlier senescence with exposure to elevated CO2. This would limit the response of ZM175 to elevated CO2 and result in photosynthetic acclimation of leaf, or photosynthetic acclimation was one of reasons for leaf senescence. |
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