著者

東村 隆子

出版者

奈良教育大学

雑誌

奈良教育大学紀要. 自然科学 (ISSN:05472407)

巻号頁・発行日

vol.38, no.2, pp.7-20, 1989-11-25

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lt was investigated in two species of dandelion. Taraxacum japonicum and T. officinale, how the elongatoin of scapes (flowering stalks) was correlated with the growth of fruits, seeds and embryos. The effect of some growth substances on the elongation of scapes was also studied by measuring the growth rate of excised segments in the solutions including various combinations of those substances. 1) The elongation of scapes shows a double-sigmoid curve and is somewhat different between two species. The early rapid elongation of scapes continues until the end of the flowering stage in T. japonicum, while it stops one day after flowering in T. officinale. The later rapid elongation starts just at begining of the ascending stage in the former species but during the prostrating stage in the latter. 2) The elongation of scapes is apparently correlated with the growth of embryos; the elongation of scapes is suspended during the rapid growth of embryos and recovered at the stage when the embryo reaches approximately 80% of full size (length). 3) The fruits grow in accordance with the enlargement of embryos in T. japonicum, while they grow almost to full size before the embryo begings a rapid growth in T. officinale. This seems to be correlated with the difference of reproduction; usual sexual reproduction in the former and asexual reproduction (apomixis) in the latter. 4) The solution including only auxin or gibberellin promotes the elongation of excised segmerits of the scapes in the budding and prostrating stages, while the solution including both auxin and gibberellin does in the later stage of flowering, This suggests the elongation is affected by the physiological age (length) of epidermal cells of scapes as well as by the amount of internal auxin.