title: Chemical hydrophobicity and uptake by plant roots.
abstract: The transpiration stream concentration factor (TSCF), the ratio between a compound's concentration in the xylem to that in the solution adjacent to the roots, is commonly used to describe the relative ability of an organic compound to be passively transported from root to shoot. Widely cited bell-shaped curves relating TSCFto the octanol/water partition coefficient (log Kow) imply that significant root uptake and transfer into shoot tissues occurs only for compounds falling within an intermediate hydrophobicity range. However, recent laboratory and field data for relatively water soluble compounds such as sulfolane, methyl tert-butyl ether (MTBE), and 1,4-dioxane suggest that these relationships are not universally applicable, especiallyfor nonionizable, highly polar, water soluble organics. To re-evaluate the relationship between root uptake and chemical hydrophobicity, TSCFs were measured for 25 organic chemicals ranging in log Kow from -0.8 to 5 using a pressure chamber technique. Using the TSCF values measured in this study, a new empirical relationship between TSCF (0 and 1) and log Kow (-0.8 to 5) is presented that indicates that nonionizable, polar, highly water soluble organic compounds are most likely to be taken up by plant roots and translocated to shoot tissue.
authors.affiliation: Utah Water Research Laboratory, Utah State University, 8200 Old Main Hill, Logan, Utah 84322, USA.
authors.forename: Erik M
authors.initials: EM
authors.lastname: Dettenmaier
authors.forename: William J
authors.initials: WJ
authors.lastname: Doucette
authors.forename: Bruce
authors.initials: B
authors.lastname: Bugbee
mesh_terms: D002110:Caffeine / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D018551:Solanum lycopersicum / Q000187:drug effects / Q000378:metabolism; D008627:Mercuric Chloride / Q000494:pharmacology; D009930:Organic Chemicals / Q000378:metabolism*; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism*; D018526:Plant Transpiration / Q000187:drug effects; D011312:Pressure; D013025:Glycine max / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D009930:Organic Chemicals; D002110:Caffeine; D008627:Mercuric Chloride