水体氮浓度对狐尾藻和金鱼藻片段萌发及生长的影响

为了厘清水体氮浓度对沉水植物片段萌发及生长的影响，通过模拟控制试验，设计了水体总氮浓度分别为0 (CK)、 0.5 mg/L (N1)、 2 mg/L (N2)、 8 mg/L (N3)和12 mg/L (N4）共5个处理，研究了水体不同氮浓度条件下狐尾藻 (Myriophyllum spicatum) 和金鱼藻 (Ceratophyllum demersum)片段(3节)萌芽数、 萌发位置、 芽长和生物量的差异。结果表明, 水体氮浓度对不同沉水植物片段萌发的影响存在差异，较高的水体氮浓度不利于狐尾藻片断萌发，而对金鱼藻片段却有一定程度的促进；氮浓度处理促进了狐尾藻顶端优势，却抑制了金鱼藻的顶端优势。狐尾藻以0.5 mg/L处理的芽长较长，生物量以2 mg/L处理最大；而金鱼藻以8 mg/L处理芽长最长，生物量以2 mg/L处理最大。由此可见，不同沉水植物对水体氮适应性存在差异，水体氮浓度较低时，沉水植物断枝可以进行萌发和生长, 而当氮浓度超过2 mg/L时，对沉水植物断枝萌发及生长反而有抑制作用；金鱼藻片段比狐尾藻对水体氮浓度的耐受性强。

Effects of nitrogen concentration in water on the germination and growth of Myriophyllum spicatum and Ceratophyllum demersum fragments

Hydrophyte especially the submerged macrophytes are important primary producer and main contributor to the subprime productivity in the water ecosystem. Improper agriculture and industry practices have led to deteriorated water quality, and eutrophication is one of the most pressing problems. The quantity of many kinds of hydrophytes,  especially submerged macrophytes,  have declined and even disappeared in the world as a result. The submerged macrophytes segments keep germinating when eaten by fish and cut by boats. There is not enough information about the effect of water nitrogen concentration on the germination and growth of the submerged macrophytes. In this experiment,  the fragments with 3 nodes of M. spicatum and C. demersum were used,  the bud number,  location of bud and biomass were investigated under five nitrogen levels in water:  0 (CK),  0.5 mg/L (N1),  2 mg/L (N2),  8 mg/L (N3) and 12 mg/L (N4). The results indicate that the tolerance to high N level is different with different submerged macrophytes. The shoot length and biomass of M. spicatum were largest when the N concentration was 0.5 mg/L and 2 mg/L respectively,  those of C. demersum were largest when the N concentration was 8.0 mg/L and 2 mg/L respectively. The segment germination and growth of the submerged macrophytes would be restrained when the N concentration was higher than 2 mg/L.