Electrical and Curvature Responses of the Avena Coleoptile to Unilateral Illumination

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Abstract
Expts. were performed to detn. the electrical and curvature responses of 3 segments of the Avena coleoptile to unilateral illumination of 200 and 31,200 mcs. The usual effect of unilateral illumination on the longitudinal electrical polarity was to cause the apical level to become more electronegative to the basal region. In the apical 10 mm. of plants stimulated by 200 mcs. of light, the lighted side became electronegative to the shaded side, while in the basal 20 mm. the polarity of the response was reversed. When this dosage of light was used, the plants generally bend toward the light In all plants that bend away from the light, when 31,200 mcs. were applied, the lighted side became electropositive to the shaded side regardless of the positions of the contacts. Since the growth curvature responses of the apical 10 mm. are always toward the electronegative side of the coleoptile, the orientation of the transverse electrical polarity established by unilateral illumination is correct for it to function in an electrophoretic mechanism of lateral auxin transport.