Effect of Umbel Order and Umbellet Position on the Production and Characteristics of Seeds and on the Development and Growth of Seedlings in Angelica acutiloba Kitagawa

Abstract

Angelica acutiloba Kitagawa, Touki, is a medicinal plant belonging to the Apiaceae family. Flowering is characterized by a series of sequentially formed umbels producing seeds. The present study was carried out to analyze the effect of the umbel order and umbellet position on: (i) seed production characteristics, (ii) seed germination, (iii) seedling emergence, and (iv) seedling growth. The results showed that seed development and maturity occurred earlier in the order of primary>secondary>tertiary umbels. Accordingly, the seed weight value was higher in the order of primary>secondary>tertiary umbels, but was not different among the umbellet positions. Seeds were mainly produced on the secondary umbels. The seed germination percentage was very high (>90%) at the optimum temperature, and the seedling emergence percentage was high (>70%) under greenhouse conditions. Seed germination and seedling emergence were not affected by the umbel order and umbellet position. The values of the growth parameters (i.e. leaf area, root diameter, shoot and root dry weight) were significantly higher in the seedlings obtained from seeds on the primary umbel than in those from seeds on the secondary and tertiary umbels. The umbellet position did not affect seedling growth. Seed production, development and seedling growth were affected by the umbel order. The primary umbel produced the heaviest seeds and subsequently the most vigorous seedlings. However, a small amount of seeds was produced on the primary umbel. It is suggested that harvesting the seeds on the primary and secondary umbels at around 9 weeks after the first flowering is most important for high-quality seed production.