title: Effect of nanoparticles on red clover and its symbiotic microorganisms.
abstract: BACKGROUND
  Nanoparticles are produced and used worldwide and are released to the environment, e.g., into soil systems. Titanium dioxide (TiO2) nanoparticles (NPs), carbon nanotubes (CNTs) and cerium dioxide (CeO2) NPs are among the ten most produced NPs and it is therefore important to test, whether these NPs affect plants and symbiotic microorganisms that help plants to acquire nutrients. In this part of a joint companion study, we spiked an agricultural soil with TiO2 NPs, multi walled CNTs (MWCNTs), and CeO2 NPs and we examined effects of these NP on red clover, biological nitrogen fixation by rhizobia and on root colonization of arbuscular mycorrhizal fungi (AMF). We also tested whether effects depended on the concentrations of the applied NPs.
  
  
  RESULTS
  Plant biomass and AMF root colonization were not negatively affected by NP exposure. The number of flowers was statistically lower in pots treated with 3 mg kg(-1) MWCNT, and nitrogen fixation slightly increased at 3000 mg kg(-1) MWCNT.
  
  
  CONCLUSIONS
  This study revealed that red clover was more sensitive to MWCNTs than TiO2 and CeO2 NPs. Further studies are necessary for finding general patterns and investigating mechanisms behind the effects of NPs on plants and plant symbionts.
authors.affiliation: Agroscope, Institute for Sustainability Sciences ISS, 8046, Zurich, Switzerland.|Plant-Microbe-Interactions, Department of Biology, Utrecht University, 3508 TB, Utrecht, The Netherlands.
authors.forename: Janine
authors.initials: J
authors.lastname: Moll
authors.affiliation: Agroscope, Institute for Sustainability Sciences ISS, 8046, Zurich, Switzerland.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gogos
authors.affiliation: Agroscope, Institute for Sustainability Sciences ISS, 8046, Zurich, Switzerland.
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Bucheli
authors.affiliation: Agroscope, Institute for Sustainability Sciences ISS, 8046, Zurich, Switzerland.
authors.forename: Franco
authors.initials: F
authors.lastname: Widmer
authors.affiliation: Agroscope, Institute for Sustainability Sciences ISS, 8046, Zurich, Switzerland. marcel.vanderheijden@agroscope.admin.ch.|Plant-Microbe-Interactions, Department of Biology, Utrecht University, 3508 TB, Utrecht, The Netherlands. marcel.vanderheijden@agroscope.admin.ch.|Institute of Evolutionary Biology and Environmental Studies, University of Zurich, Winterthurerstrasse 190, 8057, Zurich, Switzerland. marcel.vanderheijden@agroscope.admin.ch.
authors.forename: Marcel G A
authors.initials: MG
authors.lastname: van der Heijden
mesh_terms: D002563:Cerium / Q000737:chemistry / Q000378:metabolism*; D038821:Mycorrhizae / Q000187:drug effects / Q000502:physiology; D053758:Nanoparticles / Q000737:chemistry / Q000378:metabolism*; D037742:Nanotubes, Carbon / Q000737:chemistry*; D009586:Nitrogen Fixation / Q000187:drug effects; D012988:Soil Microbiology; D014025:Titanium / Q000737:chemistry / Q000378:metabolism*; D029921:Trifolium / Q000187:drug effects* / Q000382:microbiology* / Q000502:physiology
chemical_list: D037742:Nanotubes, Carbon; C009495:titanium dioxide; D002563:Cerium; C030583:ceric oxide; D014025:Titanium
keywords: Agriculture; Beneficial soil microbes; Crop; Ecosystem services; Nanomaterials