37.重力刺激によって変動するサクラジマダイコン黄化芽生えに含まれる生理活性物質(口頭発表)

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Radish (Raphanus sativus L. var. hortensis f. gigantissimus Makino) seedlings were grown under various gravity conditions in the dark. A compound content in the etiolated radish hypocotyls was decreased under simulated microgravity conditions on a 3-dimensional clinostat, but increased under 500g gravity produced by centrifugation, comparing to 1g conditions. It was isolated from etiolated radish hypocotyls grown on 1g conditions and identified to be 1-β,4-di-0-(4-hydroxy-3,5-dimethoxycinnamoyl) gentiobiose, raphanusol A which showed a potent growth-inhibiting activity for radish hypocotyl growth, based on its spectral data. The distribution of endogenous raphanusol A between the epidermis of the upper and lower flank of radish hypocotyls during gravitropic curvature was analyzed using a physicochemical assay. Gravitropic stimulation increased raphanusol A content in the upper flank within 30min after the onset of gravitropic stimulation, whereas that in the lower flank was similar to that in the controls. Previously we reported that a major factor in gravitropism in radish hypocotyls is the suppression of growth on the upper side of hypocotyls, but not the acceleration on the lower side. These results suggest that raphanusol A plays a role in controlling radish hypocotyl growth in response to various gravistimuli, especially in differential growth in gravitropism of radish hypocotyls.
2009-10-06