氮添加对长序榆C、N、P养分含量及非结构性碳水化合物含量的影响

Effects of Nitrogen Addition on Contents of C,N and P Nutrient and Non-Structural Carbohydrate in Ulmus elongata

【目的】通过研究外源氮添加,模拟氮沉降对濒危植物长序榆碳、氮、磷养分积累及其之间的计量关系及非结构性碳水化合物(NSC)含量的影响,以期为在氮沉降持续增加的背景下保护该极小种群提供参考。【方法】通过精确定量对1年生长序榆实生苗施加不同浓度的氮素,分析施氮后长序榆根、茎、叶中总碳、氮和磷的积累及其之间的计量关系和非结构性碳水化合物含量的变化。【结果】高氮量(N:262.3 mg·L-1)添加后,显著降低长序榆叶生物量,对根茎生物量没有明显影响。低氮(N:52.46 mg·L-1)和高氮均会提高根中总碳含量,但显著降低叶中总碳含量。高氮处理下,根茎叶中的总氮含量显著提高,总磷含量则会随着施氮水平的提高而显著降低。低氮和高氮处理均会降低植株中的C∶N值,C∶P和N∶P均表现在高氮处理下最高。低氮和高氮处理均会提高根、茎中可溶性多糖和淀粉含量。高氮处理显著降低叶中可溶性多糖和淀粉含量。非结构性碳水化合物含量随施氮水平的增加,在根和茎中先降低后升高,在叶中为先升高后降低。高氮处理导致Pn、Gs、Tr、WUE和Ls不同程度下降,Ci表现上升。【结论】高氮处理长序榆,提高了叶片N含量,抑制叶片的光合性能,降低碳物质积累,加剧磷素限制,由此提高其濒危的风险。同时,更多的非结构性碳水化合物在长序榆根中积累,以应对高氮对其造成的不利影响。

【Objective】Under the background of increasing nitrogen deposition,the effects of nitrogen deposition on carbon,nitrogen and phosphorus accumulation of endangered Ulmus elongata and their quantitative relationship and non-structural carbohydrate content were studied by adding exogenous nitrogen,so as to provide reference for the protection of this minimal population.【Method】The accumulations of total carbon,nitrogen and phosphorus in roots,stems and leaves of U.elongata and their quantitative relationships between those nutrients and changes of non-structural carbohydrate contents were analyzed by applying different concentrations of nitrogen to the annual seedlings of U.elongata.【Result】The leaf biomass was significantly reduced with the addition of high nitrogen(N:262.3 mg·L-1),but the root or stem biomass was not significantly affected.Both low nitrogen(N:52.46 mg·L-1)and high nitrogen treatment increased the total carbon content in roots,but significantly decreased the total carbon content in leaves.Under high nitrogen treatment,the total nitrogen content in roots,stems and leaves increased significantly,while the total phosphorus content decreased significantly with the increase of nitrogen application level.Both low and high nitrogen treatments reduced the C∶N value in the plant,however C∶P and N∶P were the highest under high nitrogen treatment.The soluble polysaccharides and starch contents in roots and stems were increased under both low and high nitrogen treatments.The content of soluble polysaccharide and starch in leaves was significantly decreased by high nitrogen treatment.The content of non-structural carbohydrates(NSC)first decreased and then increased in roots and stems,and in leaves NSC was contrary to roots and stems with the increase of nitrogen application level.High nitrogen treatment led to the decrease of Pn,Gs,Tr,WUE and Ls in varying degrees,but the increase of Ci concentration.【Conclusion】High nitrogen treatment increases N content in Ulmus elongates,and however inhibits the leaf photosynthesis,reduces the carbon accumulation and increases the phosphorus limitation,which increases the risk of endangerment.At the same time,U.elongata copes with the adverse effects of high nitrogen by accumulating more NSC in roots.