不同底质和透明度下马来眼子菜的表型可塑性研究

马来眼子菜(Potamogeton malaianusMiq.)是目前太湖沉水植物优势种之一。文章比较分析了3种不同底质和透明度情况下马来眼子菜的生长特征,探索其在太湖不断扩展的原因及其适应性。分别选取粘土质粉砂、粉砂和下蜀黄土底质上生长的马来眼子菜进行观察试验。结果表明,这3种底质在粒度组成、营养盐和分布特征上具有显著差异。在太湖粘土质粉砂和粉砂底质上马来眼子菜的生物量比下蜀黄土底质上的马来眼子菜高,其生物量随着底质营养盐的增加而增加。马来眼子菜与觅光相关的形态指标,如高度、节间距、节数、叶数、叶长及叶面积均随着底质营养盐的增加而显著增加。马来眼子菜的冠层高度与水体的透明度呈显著负相关,表明其对剧烈变化的湖泊光环境具有很强的适应能力。马来眼子菜在不同底质上的形态可塑性是其优先占据湖泊资源成为优势种的重要原因。

The phenotypic plasticity of Potamogeton malaianus Miq. on the effect of sediment shift and Secchi depth variation in Taihu Lake

The abundance and composition of aquatic macrophytes community has a great effect on a shallow lake ecosystem. Shallow lakes that support abundant aquatic macrophytes when the water is clear may be degraded by excessive nutrient inputs. Such degraded lakes are often turbid and devoid of aquatic vegetation. Taihu Lake is among the five largest fresh water lakes in China. Its ecosystem has deteriorated due to the increasing amount of pollutants discharged into the water body since the 1980s. Some aquatic macrophyte species decreased gradually and some even disappeared entirely, while Potamogeton malaianus Miq. is becoming one of the dominant species in Taihu Lake during the past 20 years. The effect of sediment shift and Secchi depth variation on the morphological plasticity of the dominant submerged macrophyte P. malaianus was examined in Taihu Lake and outdoor pond experiments. Silty clay loam, silt and Xiashu loess show different effects on the growth characteristics of P. malaianus. The results show that the nutrient concentration in the silty clay loam sediment will increase the biomass allocation than that in Xiashu loess sediment. The shoot length, internodes length, number of nodes, number of leaves, leaf length and leaf area differ in different sediments. P. malaianus showed a great morphological plasticity on canopy height in response to sediment shift and Secchi depth . The morphological traits related to light forging behavior increased significantly with the increase of the sediment nutrient. The traits include shoot length, internodes length, number of nodes, number of leaves, leaf length and leaf area. A significant negative correlation between canopy height of P. malaianus and water transparency indicates its high adaptive capacity to the drastically changing light environment of Taihu Lake. The morphological plasticity of P. malaianus on different sediments contributes greatly to its dominant status in Taihu Lake.