INTRACELLULAR MAGNETOPHORESIS OF AMYLOPLASTS AND INDUCTION OF ROOT CURVATURE

High-gradient magnetic fields (HGMFs) were used to induce intracellula r magnetophoresis of amyloplasts. The HGMFs were generated by placing a small ferromagnetic wedge into a uniform magnetic field or at the ga p edge between two permanent magnets. In the vicinity of the tip of th e wedge the dynamic factor of the magnetic field, V(H-2/2), was about 10(9) Oe(2) . cm(-1), which subjected the amyloplasts to a force compa rable to that of gravity. When roots of 2-d-old seedlings of flax (Lin um usitatissimum L.) were positioned vertically and exposed to an HGMF , curvature away from the wedge was transient and lasted approximately Ih. Average curvature obtained after placing magnets, wedge and seedl ings on a 1-rpm clinostat for 2h was 33 +/- 5 degrees. Roots of horizo ntally placed control seedlings without rotation curved about 47 +/- 4 degrees. The time course of curvature and changes in growth rate were similar for gravicurvature and for root curvature induced by HGMFs. M icroscopy showed displacement of amyloplasts in vitro and in vivo. Stu dies with Arabidopsis thaliana (L.) Heynh. showed that the wild type r esponded to HGMFs but the starchless mutant TC7 did not. The data indi cate that a magnetic force can be used to study the gravisensing and r esponse system of roots.