Poplar, oak, merbau, western redcedar, tatajuba and ipe wood biomass was leached with EtOH at 70 degrees C. The leachates were used for accelerating the duckweed growth and increasing the chlorophyll content at concns. 2.5, 10, 30 and 100 mg/dm(3) in 96 h long study. The oak and ipe leachafes showed the higest toxicity against duckweed while the merbau leachate increased the biomass growth. The chlorophyll content decreased with increasing the concn. of the leachates.