Impact des métaux lourds sur les interactions plante/ver de terre ...

SUMMARYtel-00486649, version 1 - 26 May 2010The objective of this work was to study the interactions between phytoremediating plantLantana camara (Verbenaceae), the earthworm Pontoscolex corethrurus (Glossocolecidae)and microorganisms in soil contaminated with lead.Initially, it appears that in the contaminated soil, the presence of earthworm leads to anincrease in the biomass of root and aerial parts of plants and increased absorption of lead.The physico-chemical characterization of root-aggregates showed that the activity ofearthworms increases the rate of organic matter, cation exchange capacity, total nitrogen, totaland available potassium. Moreover, the presence of earthworms increases certain enzymaticactivities in the rhizosphere. The increased growth of L. camara could result from thesedifferent actions.The action of earthworm on plants would be through terrestrial microbial-communities.Thus, the biomass of microorganisms, bacteria and fungi, of root-aggregates increase in thepresence of earthworms. By PCR-DGGE, we were unable to demonstrate differences intaxonomic diversity of the bacteria community but the analysis of physiological profiles withBiolog plates showed that the activities of earthworm enhance the functional diversity of soilbacteria. In other hand, the restructuring of fungal taxonomy has been clearly observed by theactivity of earthworm. All changes observed can explain increased growth of plants andimproved phytoextraction of heavy metal.Finally, the study underlines the role of the earthworms on the growth and thephytoextraction efficiency of the plants. So, the combination of earthworm P. corethrurus andplant L. camara could be considerable potential for the treatment of industrial sites pollutedwith lead.Key words: Heavy metal, phytoextraction, Lantana camara, earthworm, Pontoscolexcorethrurus, enzymatic activity, physic-chemical, terrestrial microflora, structure diversity,functional diversity.