Poster: Tropisms

Abs # 666: Noise-amplification of gravisensing

Presenter:	Ma, Zhong , zxm1769@louisiana.edu
Authors	Ma, Zhong  (A)   Hasenstein, Karl H (A)
Affiliations:	(A): University of Louisiana.edu

A common problem in sensory physiology is the detection of a weak signal, such as the repositioning of statoliths (amyloplasts) in gravisensing cells from a noisy background. Work on stochastic resonance and related nonlinear noise-assisted effects suggests that mechanoreceptors may perceive weak signals by noise amplification. We investigated possible dependency of the gravistimulus, a physically weak signal, on thermodynamic or vibrational noise by examining the effect of oscillating flax roots at different frequencies and amplitudes either vertically or laterally. Fifteen min stimulation was applied either prior to or during the first 15 minutes of gravistimulation. The oscillation was either parallel or perpendicular to the root axis. Our data show that initial curvature was most effectively enhanced by oscillations of 5 Hz and 0.49 mm amplitude. On average, vertically oscillated roots reached half-maximal curvature 32 min after reorientation, about 18 min earlier than non-oscillated roots. Vertical oscillation at 10 or 20 Hz during the early phase of reorientation also exhibited enhanced sensitivity of roots to gravity, whereas 80 Hz had no effect. Our data indicate that graviresponse and noise effects differ with the age of roots, and that gravisensing may be enhanced by or dependent on thermodynamic noise. Supported by NASA grant NAG10-190