Growth and stress responses of Nuttall's waterweed Elodea nuttallii (Planch) St. John to water movements

Understanding the interactions between aquatic plants and environmental factors is important to clarify aquatic ecosystem functioning. The mechanisms governing the interactions between water flow and plants are not yet fully understood, and the responses of plants to main flow (without turbulence) compared to turbulence are largely unknown. Here, we compared the growth and stress responses of the aquatic macrophyte Elodea nuttallii to exposure to turbulence and main flow. Turbulence and main flow were generated using a vertically oscillating horizontal grid and a recirculating system, respectively and the experiment lasted for 3 weeks. A decrease in shoot elongation coupled with an increase in radial expansion was observed in plants exposed to water movements. These effects were further accompanied by significant increases in cellulose and lignin. Turbulence reduced total chlorophyll by approximately 40% compared to plants in the control and main flow. Mechanical stress induced by turbulence leads to increased oxidative stress and tissue rigidification. The turbulence triggered stress in E. nuttallii is more severe than that induced by main flow. Our findings can offer insights for explaining the habitat preferences of macrophytes and contribute to a better planning of the criteria that benefit in aquatic ecosystem management.