高浓度CO2下氮素对小麦叶片干物质积累及碳氮关系的影响

高大气CO₂浓度下植物叶片干物质积累、碳氮关系和糖含量的变化对光合作用的适应性下调有重要的反馈作用,通过研究不同施氮量对高大气CO₂浓度下植物叶片干物质积累、叶氮浓度和糖含量的影响,可进一步明确氮素对植物光合作用适应性下调的调控机制。以不同大气CO₂浓度和氮素水平为处理条件,测定盆栽小麦拔节期叶片鲜重、干重、含水量、还原糖、可溶性糖、全氮含量,研究了氮素对长期高大气CO₂浓度(760μmol·mol-1)下小麦叶片的干物质积累、糖含量及碳氮含量的影响。结果表明,大气CO₂浓度升高使小麦叶片的鲜重和干重增加,含水量下降。大气CO₂浓度升高使N0处理的小麦叶片还原糖含量下降,而可溶性糖含量显著升高;施氮后小麦叶片还原糖含量无显著变化,但可溶性糖含量降低。高大气CO₂浓度条件下小麦叶片全氮含量下降,C/N比增加,而增施氮素后C/N比显著下降。可溶性糖含量和C/N比的下降有利于减轻同化物质对光合作用的反馈抑制,提高大气CO₂浓度增高条件下小麦叶片的P_n。

EFFECTS OF NITROGEN ON THE DRY MATTER ACCUMULATION,CARBON ANDNITROGEN METABOLISM OF WHEAT LEAVES UNDER ELEVATED ATMOSPHERIC CO2 CONCENTRATION

The photosynthetic down-regulation in plant leaves under elevated atmospheric CO2 may be related to the changes of the relationship between nitrogen and carbon, and soluble sugars content in plant leaves. It is helped to investigate the effect of nitrogen application on the dry matter accumulation, foliar N concentration and soluble sugar content and determine the regulatory mechanism of nitrogen application on photosynthetic down-regulation under elevated atmospheric CO2 concentration. A pot experiment was conducted to wheat treated by different atmospheric CO2 concentrations and nitrogen application rates, the fresh weight, the dry weight, moisture content, foliar N concentration, reductive and soluble sugar content measured in this, to understand the effect of nitrogen application on the dry matter accumulation and nitrogen-carbon relationship in wheat flag leaves under elevated atmospheric CO2 concentration (760μmol ·mol-1). The results showed that elevated CO2] increased the fresh weight and the dry weight,but decreased moisture content in wheat leaves, at the same time, elevated CO2] decreased reductive sugar content, but increased soluble sugar content in wheat leaves in N 0 treatment. However, the reductive sugar content did not change significantly, the soluble sugar increased significantly while nitrogen supplied. Consequently, elevated CO2] decreased foliar N content, increased C/N ratio, nitrogen application decreased C/N ratio and soluble sugar content. The decrease of C/N ratio and soluble sugar content was beneficial to relieve the feedback inhibition of assimilation matter on photosynthesis, increase net photosynthetic rate under elevated atmospheric CO2 concentration.