title: Root uptake of lipophilic zinc-rhamnolipid complexes.
abstract: This study investigated the formation and plant uptake of lipophilic metal-rhamnolipid complexes. Monorhamnosyl and dirhamnosyl rhamnolipids formed lipophilic complexes with copper (Cu), manganese (Mn), and zinc (Zn). Rhamnolipids significantly increased Zn absorption by Brassica napus var. Pinnacle roots in (65)Zn-spiked ice-cold solutions, compared with ZnSO4 alone. Therefore, rhamnolipid appeared to facilitate Zn absorption via a nonmetabolically mediated pathway. Synchrotron XRF and XAS showed that Zn was present in roots as Zn-phytate-like compounds when roots were treated with Zn-free solutions, ZnSO4, or Zn-EDTA. With rhamnolipid application, Zn was predominantly found in roots as the Zn-rhamnolipid complex. When applied to a calcareous soil, rhamnolipids increased dry matter production and Zn concentrations in durum (Triticum durum L. cv. Balcali-2000) and bread wheat (Triticum aestivum L. cv. BDME-10) shoots. Rhamnolipids either increased total plant uptake of Zn from the soil or increased Zn translocation by reducing the prevalence of insoluble Zn-phytate-like compounds in roots.
authors.affiliation: Soil and Land Systems, School of Earth and Environmental Sciences, The University of Adelaide, PMB 1, Glen Osmond, SA 5064, Australia. samuel.stacey@adelaide.edu.au
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Stacey
authors.forename: Michael J
authors.initials: MJ
authors.lastname: McLaughlin
authors.forename: Ismail
authors.initials: I
authors.lastname: Cakmak
authors.forename: Ganga M
authors.initials: GM
authors.lastname: Hettiarachchi
authors.forename: Kirk G
authors.initials: KG
authors.lastname: Scheckel
authors.forename: Michael
authors.initials: M
authors.lastname: Karkkainen
mesh_terms: D000042:Absorption; D029688:Brassica napus / Q000378:metabolism; D006017:Glycolipids / Q000008:administration & dosage / Q000378:metabolism*; D007700:Kinetics; D018517:Plant Roots / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D010944:Plants / Q000378:metabolism*; D012987:Soil / Q000032:analysis; D013057:Spectrum Analysis; D014908:Triticum / Q000378:metabolism; D015032:Zinc / Q000032:analysis / Q000378:metabolism*
chemical_list: D006017:Glycolipids; D012987:Soil; C418382:rhamnolipid; D015032:Zinc