MICROBIAL UTILIZATION OF BLACK POPLAR (POPULUS-NIGRA L) LEAF LEACHATE

A two weeks' black poplar (Populus nigra L.) leaf water leachate to wh ich [C-14]-labelled substrates had been added was used to determine mi crobial utilization rates and efficiency of the water-extracted fracti ons. Microbial utilization rate was dependent on the concentration of individual fractions in the leachate. Leachate alone showed no inhibit ory effect on microbial uptake rates of added [C-14]-labelled substrat es. The transformation efficiency of the radioactively labelled substr ates into microbial biomass ranged from 27.4 to 99.9% and incorporatio n rates ranged from 2.4 to 85.3%. A relatively high portion of the dis solved fractions of the leachate (up to 54.4%) was utilized by the mic robial assemblage during a 20 h incubation period. This indicates that a significant part of the leachable material is incorporated at a hig h rate into microbial biomass as an easily available source bf nutrien ts. The extent and the high rate of leachate utilization by microorgan isms in hydromelioration channels loaded with a poplar leaf detritus d emonstrates an integration of this process into the general food web o f the water ecosystems.