Differences in leaf nitrogen content, photosynthesis, and resource-use efficiency between Eichhornia crassipes and a native plant Monochoriavaginalis in response to altered sediment nutrient levels

Eichhornia crassipes is one of the world’s most prevalent invasive aquatic plants, causing significant ecological and socio-economic impacts in introduced areas. In this study, we compared the leaf resource capture- and use-related traits of E. crassipes with its confamilial native aquatic plant Monochoria vaginalis at three nutrient levels. Our results showed that leaf nitrogen content based on mass, leaf nitrogen content based on area, N:C, photosynthetic rate, specific leaf area, and leaf construction cost of E. crassipes increased significantly with increasing levels of nutrition, the mean values of these traits increased 0.55, 0.35, 0.51, 0.43, 0.21, and 0.07 times from low nutrient level to high, respectively. These traits (except for the leaf construction cost) in M. vaginalis remained unchanged. At low nutrient level, M. vaginalis had a higher leaf nitrogen content, N:C, photosynthetic rate, specific leaf area, and water-use efficiency than E. crassipes. At high nutrient level, E. crassipes had a higher photosynthetic rate and photosynthetic nitrogen-use efficiency than M.vaginalis, suggesting that the invasiveness of E. crassipes was dependent on the availability of resources in environment. In addition, our results supported the fluctuating resources hypothesis, indicating that an increased level of nutrients in the environment will increase the invasiveness of E. crassipes.