Effect of seed selection based on seed weight and specific gravity on seed germination and seedling emergence and growth in Angelica acutiloba Kitagawa

Ninh Thi Phip, H. Nojima and T. Tashiro, Jpn. J. Tropical Agric., 50: 154-162

Abstract : Angelica acutiloba Kitagawa (Touki) is a perennial medicinal plant used as a natural drug, in Japan and in many other Asian countries. Seed germination and seedling growth are critical for species survival, plant quality and productivity. However, the seed characteristics (e.g. seed weight and specific gravity) and the optimal temperature, which affect the germination of Touki seeds and seedling growth, have not been reported. In the present study, a suitable method for classifying seeds based on the specific gravity and seed weight was applied. Experiments were conducted to examine the effect of seed weight and specific gravity on the germination of Touki seeds in the laboratory, and seedling emergence and growth in a closed system. Also the effect of the temperature on seed germination was examined. The results showed that the optimal temperature for germination was 20.0｡ﾉ. Selecting seeds based on the seed weight showed that by increasing the seed weight, the germination percentage increased and seedling growth was promoted. The root diameter and the values of the total plant dry weight were higher in the seedlings obtained from heavier seeds than in those obtained from lighter seeds. Root/shoot ratio was relatively higher in the seedlings obtained from heavier seeds than in those obtained from lighter seeds. Water uptake was affected by the seed weight. Lighter seeds absorbed water faster than heavier seeds. Selecting seeds based on the specific gravity enabled to increase the seed germination percentage, and seedling emergence and quality. The root /shoot ratio tended to be higher in the seedlings obtained from seeds with a higher specific gravity. Heavy seeds with a high specific gravity produced highly vigorous seedlings.
Key words: Germination temperature, Medicinal plant, Seed characteristics, Touki.