Effects Of Atmospheric CO₂ Enrichment And Nitrogen Application Rate On Photosynthetic Parameters,stomatal Parameters And Water Use Efficiency Of Spring Wheat

Plant photo-physiology would be changed under atmospheric CO₂ enrichment conditions, the mechanism of photosynthetic down-regulation and its nitrogen regulation was one of the focus topic in plant physiological field. Using the Top Open Chambers simulated the elevated atmospheric CO₂ concerntration, wheat (Triticum aestivum L.) was grown under different N application levels and atmospheric CO₂ concerntration, the net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) and intercellular CO₂ concentration (Ci) of spring wheat leaves which exploure of different atmospheric CO₂ concerntration were measured by a protable photosynthetic measurement system, the leaf water use efficiency (WUE) and stomatal limitation value also be cauculated in this potted experiment, to study the response of photosynthesis and WUE to atmospheric enrichment and its regulation mechnism of nitrogen application. The results shown that Pn, Ci, Ls and WUE were increased, but Gs decreased gradually, and Tr decreased first and then increased with nitrogen levels increasing under high atmospheric CO₂ concentration conditions.Compared to ambiment atmosphric CO₂ treatments, Pn was decreased significantly in 0g,0.1g N·kg^-1(soil) treatments and significantly increased in 0.2g N·kg-1 treatment which exploure of different atmospheric CO₂ concerntration, Gs, Ci and Tr were decreased. Ls and WUE were highest in 0.2g N·kg-1, and the differences were significant compared to the other treatments. Pn and Ls were significantly increased with nitrogen levels under the condition of different atmospheric CO₂ concerntration. but the response of Ci.and Tr were inconsistent. So,WUE and Ls was significantly increased under long-term high CO₂ concentration. The photosynthetic down-regulation was occured in 0g,0.1g N·kg^-1, but not occured under the 0.2g N·kg-1 treatment. Meanwhile, the stomatal as the main channel of plants and the atmosphere CO₂ and water vapor exchange. In 760μmol mol-1CO₂ concentration,the changes of stomatal parameters are inconsistent,To compared with 400μmol mol-1,the stomatal density and stomatal width was reduced,and stomatal length was significantly increased.But stomatal opening have not significantly change. The performance of stomatal parameters were also inconsistent under different nitrogen concentrations.With the nitrogen concentration,stomatal density was significantly lower in turn, and the difference reached a significant level, while the stomatal length,width,and stomatal opening were significantly increased in turn.In 760μmolmol^-1CO₂ concentrations,the stomatal parameters and Cond, Ci and WUE correlation between the performance of all discrepancies, including stomatal density and Cond and Ci become very significant negative correlation,and no correlation with WUE. Stomatal opening and Cond,Ci have a very significant positive correlation but in contrast to WUE. Cond and Ci stomatal length were not correlated,but have a significant positive correlation with WUE.stomatal width and Cond and Ci have a significant positive correlation, but no correlation with WUE. Either in 400μmolmol^-1CO₂ treatments or 760μmolmol^-1CO₂ treatments,stomatal density, stomatal opening and Cond,Ci and WUE have same correlation.The related performance of stomatal length,stomatal width and Cond and Ci and WUE are basically the same,and the performance of the stomal length and width of both Ci and Cond were significantly positively correlated,but have a very significant negative correlation with WUE.And in 760μmolmol^-1CO₂ treatments, stomatal density and stomatal opening have a significant negative correlation,Stomatal length, stomatal width and stomatal density have no correlation,while in the control group, stomatal opening,stomatal length and stomatal density there was a significant correlation, but have no correlation between stomatal width and stomatal density.Under different nitrogen concentrations, stomatal density and Cond are forming a very significant negative correlation with the Ci and WUE. but have highly significant positive correlation with the Ci and WUE. And different nitrogen concentrations have no impact on stomatal density and Cond, Ci and WUE relationship. in N₂₀₀ treatments,Stomatal opening and Cond, Ci and WUE were not correlated, in the N₁00 treatment, stomatal opening and Cond is also no correlation, but with Ci and WUE have a significant positive correlation. In the N₀ treatment, stomatal opening and Cond have a very significant positive correlation, between with Ci and WUE has significant negative correlation. in N₀ and N₁₀₀ treatments, between stomatal length and cond, there was significant negative correlation, with Ci and WUE have a significant positive correlation. But the performance in the N₂00 treatments were the opposite. Stomatal width and Cond had significant positive correlation under N₀ treatment,with Ci and WUE have a significant negative correlation. In N₁₀₀ treatments, stomatal width and Ci were significantly correlated, but not correlated with Cond and WUE. In N₂₀₀ treatments,stomatal width and Cond, Ci and WUE were not correlated. In N₀ treatment,the stomatal density and stomatal opening has a significant positive correlation,but significantly negatively correlated with stomatal length and stomatal width.In N₂₀₀ and N₁₀₀ treatments, stomatal density and stomatal opening, stomatal width have no correlation.