02641naa a2200181 a 450000100080000000500110000800800410001910000130006024500730007326000090014652019010015570000170205670000140207370000150208770000160210270000200211877303210213813148582008-09-18       2008    bl uuuu     u00u1 u    #d1 aJANA, U.  aEarthworm impact on the model plant Arabidopsis thaliana plasticity.  c2008  aPlants exhibit phenotypic plasticity in response to changes in their environment, such as soil composition, presence of pathogens or soil engineers like earthworms. Worms are known to improve plant growth. However, the extent of worm effects depends on plant species, worm and soil types. To date, plant plasticity in response of earthworms has essentially been assessed through measurements of biomass production. In the present work, we propose a new approach to study earthworm effects on plant plasticity in which plant phenotypic variations are correlated with variations in the expression levels of several genes involved in cellular division and responses to stress. To do so, an original experimental setup was designed in which as many parameters as possible were tightly controlled. Individual Arabidopsis thaliana plants were grown with (or without) Aporrectodea caliginosa earthworms in two types of soil, a rich one or a poor soil almost free of organic matter and nitrogen. In the poor soil, plant phenotype was typical of nitrogen-starved plants, with a reduced aerial biomass production and an over-developed root system. However, earthworms restored vegetative and reproductive biomass production to the levels observed in the rich soil. In leaves, this seemed to correspond to increased cell divisions and enhanced defence against reactive oxygen species. Regardless of soil quality, worms significantly decreased length and biomass of the root systems, suggesting an improvement of plant mineral uptake. This hypothesis was confirmed by plant C:N analyses that revealed general N enrichment in all plants. Furthermore, worms decreased ammonium contents in both soils whereas they strongly increased nitrogen content in the poor soil. These experiments clearly showed effects of worms on soil mineral status and on nutrient uptake in plants leading to better resource allocation1 aREPELLIN, A.1 aBAROT, S.1 aBLOUIN, M.1 aLAVELLE, P.1 aZUILY-FODIL, Y.  tIn: INTERNATIONAL COLLOQUIUM ON SOIL ZOOLOGY, 15; INTERNATIONAL COLLOQUIUM ON APTERYGOTA, 12., 2008, Curitiba. Biodiversity, conservation and sustainabele management of soil animal: abstracts. Colombo: Embrapa Florestas. Editors: George Gardner Brown; Klaus Dieter Sautter; Renato Marques; Amarildo Pasini. 1 CD-ROM.