| Research Abstract |
Phototropism is one of the common growth responses of plants to unilateral irradiation. Went proposed that phototropism is caused by a lateral gradient of growth-promoting auxin in the bending organ (Cholodny-Went theory). Recently, Bruinsma found that the shaded half did not contain more auxin than the illuminated ones as required by the C.-W. theory. Instead it was found that the even distribution of auxin was accompanied by a lateral gradient of growth-inhibitory substances during phototropic curvature.
We have been investigating the relationship between plant growth inhibitors and growth inhibition by light in plants, and have succeeded in isolation some light-induced growth inhibitors and these precursors related to phototropism, raphanusanins from radish (Raphanus sativus var. hortensis f. gigantissimus M.) hypocotyls, 6-methoxy-2-benzoxazolinone from light-grown maize (Zea mays L.) shoots, 3-hydroxy-β-ionone from light-grown dwarf bean (Phaseolus vulgaris) shoots, p-hydroxy cinnamic acid from light-grown bean (Vigno mango L.) seedlings, unsaturated fatty acid hydroperoxides from light-grown buckwheat (Fagopyrum esculentum) seedlings and 8-epixanthatin from sunflower (Helianthus annuus L).
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