10 ダイコン下胚軸の光屈性と制御物質(口頭発表の部)

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Phototropism is the curvature of a plant organ under the influence, and particularly also of the direction of the irradiation. Went (1928) proposed that phototropism is caused by a lateral gradient of growth-promoting auxin in the bending organ. This led to the Cholodny-Went theory of photo- and geotropic curvatures (1937). This elegant theory, is it true? Bruinsma and Hasegawa (1990) recently found that the shaded half did not contain more auxin than the illuminated one 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. In the radish seedlings, the inhibitors playing a role in phototropic curvature have been identified, and their role has been largely elucidated by Hasegawa's group. The activity is mainly exerted by raphanusanins and, to a smaller extent, by raphanusamide. The chemical structures of raphanusanins and raphanusamide were once reported to be piperidinethione and 1,3-oxazepin-2-one derivatives, respectively. However, their structures were recently revised by X-ray crystallographic structure analysis and chemical synthesis (Harada, Yamamura, and Hasegawa): raphanusanin A, (3R^*, 6R^*)-3-[methoxy(methylthio)methyl]-2-pyrrolidinethione; raphanusanin B, (3R^*, 6S^*) isomer, raphanusamide, (E)-3-methoxymethylene-2-pyrrolidinethione. The structure-activity studies of raphanusanins and analogues clarified that thioamide and thioacetal or thiomethylmethylene moieties were important for their growth inhibitory activities.
天然有機化合物討論会の論文
1992-09-10

10 ダイコン下胚軸の光屈性と制御物質(口頭発表の部)

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