Sucrose modifies growth and physiology in axenically grown Myriophyllum spicatum with potential effects on the response to pollutants.

Sucrose as a carbon source in axenic tests affects plant growth and physiology. The high sucrose concentration in Organisation for Economic Co-operation and Development (OECD) guideline 238 for the submerged growing aquatic plant Myriophyllum spicatum might modify pollutant effects, thus impairing environmental risk assessment. In a factorial design experiment with axenic M. spicatum exposed to 3 sucrose concentrations (no, low, and high) with or without cadmium, growth, dry matter content, content in pigments or phenolic compounds, and elemental stoichiometry of carbon (C), nitrogen (N), and phosphorus (P) were measured. The results show that sucrose is crucial for growth but can be used at lower concentrations than currently considered. Sucrose-treated plants had higher dry matter content and C content but lower contents of chlorophyll and N. Cadmium affected the content in chlorophyll, phenolic compounds, and elemental stoichiometry. Interactive effects were observed on length growth, C and N content, and the C:N and N:P molar ratios. Remarkably, cadmium led to increased shoot length at low, but not at high, sucrose concentration. This contrasting effect might result from differences in osmotic potential caused by sucrose. Overall, the results suggest a strong effect of sucrose concentration on the growth and physiology of M. spicatum and modifications of the response to cadmium. Further studies should establish the lowest sucrose level needed to account for realistic environmental risk assessment based on the axenic OECD 238. Environ Toxicol Chem 2017;36:969-975. © 2016 SETAC.