Phototactic responses of Chlamydomonas reinhardtii in electric fields

Abstract

Chlamydomonas reinhardtii Dangeard strain Göttingen 11 – 32(+) responds both phototactically and galvanotactically. If electric fields and a light stimulus of 496 nm were applied simultaneously, phototaxis persisted but the response was modified. Field lines perpendicular to the phototactic direction of movement inhibited phototaxis. If the field lines were parallel to the light direction, the effect depended on the position of the poles. When the cathode faced the light, an increase of the phototactic reaction values was observed. In this case electric fields enhanced positive phototaxis with increasing voltages from 3 V up to 12 V. If the cathode was on the opposite side, positive phototactic movement was inhibited. The maximum inhibition was found at 12 V. At this voltage positive phototaxis was measured neither at low nor at high fluence rates, and positive phototaxis was shown only between 0.1 and 1.5 W m−1.