The effects of paraffin oil on phototropic and geotropic responses in avena coleoptiles
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Experiments are described which were designed to test the significance of the coleoptile tip as the site of reception of light stimulus leading to negative photo-tropic response under paraffin oil. The results show clearly that the tip is of paramount importance in this respect. Further experiments in which the coleoptile tips were bisected in a plane at right angles to the light rays lend support to the hypothesis that negative phototropism under oil is related tolateral transport of material in the tip. Lastly, experiments which show that the geotropic response of coleoptiles is not reversed by immersion in oil are described. These findings are discussed in relation to certain hypotheses concerning the mechanism of negative phototropism under oil.