Does ethylene mediate the autochemotropic and rheotropic responses in Phycomyces?

We tested the hypothesis that ethylene was involved in autochemotropism (avoidance response) and rheotropism (wind response) of the sporangiophore (spph) of Phycomyces blakesleeanus Burgeff. When a solid barrier was placed 1 mm away from the growing zone of the spph, the spph grew away from the barrier. This response had a lag time of 2-4 min and persisted at least for 20 min. Coating the surface of the barrier with powdered Purafil, a strong ethylene oxidant, did not affect the avoidance response. When the spph was placed in a laminar flow of air, it grew into the wind within 2-4 min. When ethylene (200 μl l(-1)) was added to the air flow, the same positive rheotropic growth response took place. Neither autochemotropism nor rheotropism of the Phycomyces spph seem to be mediated by ethylene produced by the spph.