title: Investigating differences in the root to shoot transfer and xylem sap solubility of organic compounds between zucchini, squash and soybean using a pressure chamber method.
abstract: A pressure chamber method was used to examine differences in the root to shoot transfer and xylem sap solubility of caffeine (log Kow=-0.07), triclocarban (log Kow=3.5-4.2) and endosulfan (log Kow=3.8-4.8) for zucchini (cucurbita pepo ssp pepo), squash (cucurbita pepo ssp ovifera), and soybean (glycine max L.). Transpiration stream concentration factors (TSCF) for caffeine (TSCF=0.8) were statistically equivalent for all plant species. However, for the more hydrophobic endosulfan and triclocarban, the TSCF values for zucchini (TSCF=0.6 and 0.4, respectively) were 3 and 10 times greater than the soybean and squash (TSCF=0.2 and 0.05, respectively). The difference in TSCF values was examined by comparing the measured solubilities of caffeine, endosulfan and triclocarban in deionized water to those in soybean and zucchini xylem saps using a modified shake flask method. The measured solubility of organic contaminants in xylem sap has not previously been reported. Caffeine solubilities in the xylem saps of soybean and zucchini were statistically equal to deionized water (21500mgL(-1)) while endosulfan and triclocarban solubilities in the zucchini xylem sap were significantly greater (0.43 and 0.21mgL(-1), respectively) than that of the soybean xylem sap (0.31 and 0.11mgL(-1), respectively) and deionized water (0.34 and 0.11mgL(-1), respectively). This suggests that the enhanced root to shoot transfer of hydrophobic organics reported for zucchini is partly due to increased solubility in the xylem sap. Further xylem sap characterization is needed to determine the mechanism of solubility enhancement.
authors.affiliation: Aqua Engineering, 533 W 2600 S Suite 275, Bountiful, UT 84010, USA. Electronic address: nahog@aquaeng.com.
authors.forename: Naho
authors.initials: N
authors.lastname: Garvin
authors.affiliation: Utah Water Research Laboratory, Utah State University, 8200 Old Main Hill, Logan, UT 84322, USA. Electronic address: william.doucette@usu.edu.
authors.forename: William J
authors.initials: WJ
authors.lastname: Doucette
authors.affiliation: Connecticut Agricultural Experiment Station, 123 Huntington Street, New Haven, CT 06504, USA. Electronic address: Jason.White@ct.gov.
authors.forename: Jason C
authors.initials: JC
authors.lastname: White
mesh_terms: D002110:Caffeine / Q000032:analysis; D002224:Carbanilides / Q000032:analysis; D028464:Cucurbita / Q000187:drug effects* / Q000502:physiology; D009930:Organic Chemicals / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects* / Q000502:physiology; D018520:Plant Shoots / Q000187:drug effects* / Q000502:physiology; D011312:Pressure; D012995:Solubility; D013025:Glycine max / Q000187:drug effects* / Q000502:physiology; D013455:Sulfur / Q000032:analysis; D052584:Xylem / Q000502:physiology
chemical_list: D002224:Carbanilides; D009930:Organic Chemicals; D002110:Caffeine; D013455:Sulfur; C009540:triclocarban
keywords: Hydrophobicity; Plant uptake; Pressure chamber; Solubility; Transpiration stream concentration factor