ELECTROTROPISM OF NICOTIANA POLLEN TUBES

Electrotropism of tobacco pollen tubes towards the anode was analysed. The threshold and saturation values for the electrotropism were less than 50 mV mm-1 and 200 mV mm-1, respectively. The tropic response gradually increased with increasing duration to exposure, but no further increase in the tropic response was observed when exposure of the electric field was terminated. Pollen tubes growing towards the cathode had a tendency to burst in a strong electric field. These results suggest that an externally applied electric field acts as a motive force for electrotropism but not as a trigger and that endogenous currents play a role in tip growth of pollen tubes. Possible mechanisms responsible for the electrotropism of pollen tubes are discussed.