title: Analysis of magnetic gradients to study gravitropism.
abstract: OBJECTIVE
  Gravitropism typically is generated by dense particles that respond to gravity. Experimental stimulation by high-gradient magnetic fields provides a new approach to selectively manipulate the gravisensing system.
  
  
  METHODS
  The movement of corn, wheat, and potato starch grains in suspension was examined with videomicroscopy during parabolic flights that generated 20 to 25 s of weightlessness. During weightlessness, a magnetic gradient was generated by inserting a wedge into a uniform, external magnetic field that caused repulsion of starch grains. The resultant velocity of movement was compared with the velocity of sedimentation under 1 g conditions.
  
  
  RESULTS
  The high-gradient magnetic fields repelled the starch grains and generated a force of at least 0.6 g. Different wedge shapes significantly affected starch velocity and directionality of movement.
  
  
  CONCLUSIONS
  Magnetic gradients are able to move diamagnetic compounds under weightless or microgravity conditions and serve as directional stimulus during seed germination in low-gravity environments. Further work can determine whether gravity sensing is based on force or contact between amyloplasts and statocyte membrane system.
authors.affiliation: Biology Department, University of Louisiana at Lafayette, Lafayette, Louisiana 70504-2451, USA. hasenstein@louisiana.edu
authors.forename: Karl H
authors.initials: KH
authors.lastname: Hasenstein
authors.forename: Susan
authors.initials: S
authors.lastname: John
authors.forename: Peter
authors.initials: P
authors.lastname: Scherp
authors.forename: Daniel
authors.initials: D
authors.lastname: Povinelli
authors.forename: Susan
authors.initials: S
authors.lastname: Mopper
mesh_terms: D018522:Gravitropism / Q000502:physiology*; D060328:Magnetic Phenomena; D009068:Movement; D010944:Plants / Q000378:metabolism*; D013213:Starch / Q000378:metabolism / Q000648:ultrastructure; D014893:Weightlessness
chemical_list: D013213:Starch