Poster: Tropisms
Abs #
675: Vibrational forces and ultrasound can displace organelles inside plant gravireceptor cells.
Plant gravity perception can be studied by displacing statoliths inside receptor cells by forces other than gravity. In a plant subjected to non-symmetric vibrations dense statoliths experience inertial force, which causes their cyclic motion relative to cytoplasm and, due to complex rheology of the cell interior, can result in a net statoliths displacement, as if a “vibrational” ponderomotive force is acting on them. Vertically growing Arabidopsis seedlings, subjected to horizontal, saw-tooth shaped oscillations (250 Hz, 1.5 mm amplitude), showed 17±2o root curvature toward and shoot curvature of 11±3o against the stronger acceleration. Reversal of the oscillations polarity has lead to reversal of the direction of curvature. Control experiments with starchless mutants (TC7) produced no net curvature. Linum roots curved 25±7o. Ceratodon protonemata subjected to the same oscillations have shown displacement of plastids and curvature. Acoustic ponderomotive forces, originating from transfer of a sonic beam momentum due to sound scattering and attenuation in a mechanically heterogeneous system also can displace statoliths. Vertically growing flax seedlings curved away from the ultrasonic source (800 kHz, 0.1 W/cm2). Besides investigating the graviperception mechanism, vibrational and acoustic forces can serve as tools for analyzing mechanical properties of cell interior and can provide directional stimuli for plants in microgravity.
