Fate of polycyclic aromatic hydrocarbons in plant-soil systems: Plant responses to a chemical stress in the root zone
Plant uptake and translocation of polycyclic aromatic hydrocarbons (PAHs) from soil was investigated to explore plant-microbial interactions in response to a chemical stress in the root zone. Plant uptake of individual PAHs was examined under laboratory conditions which maximized root exposure. White sweetclover, Melilotus alba, was grown in soils dosed with [sup 14]C-naphthalene, -phenanthrene, -pyrene, and -fluoranthene. The highest [sup 14]C concentrations were associated with roots, with decreasing concentrations observed in stems and leaves; however, the greatest percentage of recoverable [sup 14]C remained in the soil ([ge]86%) for all four PAHs. No evidence of bioaccumulation of the individual PAHs was found in M. alba over a 5-day exposure period. Root uptake and translocation of PAHs from soil to aboveground plant tissues proved to be a limited mechanism for PAH transport into terrestrial food chains. However, root surface sorption of PAHs may be important for plants in soils containing elevated concentrations of PAHs. Consequently, the root-soil interface may be important for plant-microbial interactions in response to a chemical stress. [sup 14]CO[sub 2] pulse-labeling studies provide evidence of a shift in [sup 14]C-allocation from aboveground tissue to the root zone when plants were exposed simultaneously to phenanthrene in soil. In addition, soil respiration and heterotrophic plate counts of rhizosphere microorganisms increased in plants exposed to phenanthrene as compared to controls. This study demonstrates the importance of the root-soil interface for plants growing in PAH contaminated soil and provides supportive evidence for a plant-microbial defense response to chemical toxicants in the root zone. Lipophilic toxicants in soils may reach high concentrations in the root zone, but rhizosphere microbial communities under the influence of the plant may reduce the amount of the compound that is actually taken up by the root.
- Research Organization:
- Tennessee Univ., Knoxville, TN (United States)
- OSTI ID:
- 7026781
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CLOVER
PLANT GROWTH
POLYCYCLIC AROMATIC HYDROCARBONS
BIOCONVERSION
BIOLOGICAL EFFECTS
ENVIRONMENTAL EXPOSURE PATHWAY
SOILS
CONTAMINATION
BIOLOGICAL STRESS
MICROORGANISMS
NAPHTHALENE
PHENANTHRENE
PYRENE
ROOT ABSORPTION
UPTAKE
ABSORPTION
AROMATICS
CONDENSED AROMATICS
GROWTH
HYDROCARBONS
LEGUMINOSAE
MAGNOLIOPHYTA
MAGNOLIOPSIDA
ORGANIC COMPOUNDS
PLANTS
SORPTION
560300* - Chemicals Metabolism & Toxicology