Assessing the dynamic changes of rhizosphere functionality of Zea mays plants grown in organochlorine contaminated soils

The persistent organochlorine pesticides (OCPs) in soils are suspected to disturb soil biogeochemical cycles. This study addressed the dynamic changes in soil functionality under lindane and chlordecone exposures with or without maize plant. Decreases in soil ammonium concentration, potential nitrogen mineralization and microbial biomass were only OCP-influenced in bulk soils. OCPs appeared to inhibit the ammonification step. With plants, soil functionality under OCP stress was similar to controls demonstrating the plant influence to ensure the efficiency of C- and N-turnover in soils. Moreover, OCPs did not impact the microbial community physiological profile in all tested conditions. However, microbial community structure was OCP-modified only in the presence of plants. Abundances of gram-negative and saprophytic fungi increased (up to +93% and +55%, respectively) suggesting a plant stimulation of nutrient turnover and rhizodegradation processes. Nevertheless, intimate microbial/plant interactions appeared to be OCP-impacted with depletions in mycorrhizae and micro/meso-fauna abundances (up to -53% and -56%, respectively) which might have adverse effects on more long-term plant growth (3-4 months). In short-term experiment (28days), maize growth was similar to the control ones, indicating an enhanced plasticity of the soil functioning in the presence of plants, which could efficiently participate to the remediation of OCP-contaminated soils.