A phytotoxicity test using transpiration of willows

A short-term acute toxicity assay for willow trees growing in contaminated solution or in polluted soil was developed and tested. The test apparatus c onsists of an Erlenmeyer flask with a prerooted tree cutting growing in it. Growth and reduction of transpiration are used to determine toxicity. Tran spiration is closely related to photosynthesis and growth, but is easier an d faster to measure and can be measured without disturbance of the test sys tem. Plants are grown for 24 h in uncontaminated nutrient solution before t he toxicant is added to determine the initial transpiration. The loss of we ight is expressed as % decrease after 48 and 72 h or longer compared to the initial transpiration, divided by the transpiration of control plants. Mor e toxicity parameters are growth and water use efficiency of the plants. Th e sensitivity of the test was evaluated with 3,5-dichlorophenol. EC50 value s between 5.8 and 9.6 mg/L were found. This is similar to the results from algal growth rate tests. The willow tree toxicity test may be useful for de termining the site-specific toxicity of polluted soils and for terrestrial risk assessment of new chemicals and pesticides.