ペレット種子を用いたセンブリ機械播種技術の開発

抄録

Because the seeds of Swertia japonica (Schult.) Makino, the source plant of the crude drug Swertiae herba, are tiny, they are conventionally sown by suspending them in water. However, this method has the disadvantage that the seeds are sown irregularly and often too densely, which can lead to stunted growth and plant disease susceptibility. To control the seed density of S. japonica, we manufactured pelleted seeds, and investigated seeding conditions using a commercially available vegetable seeder. The germination rate of pelleted seeds was as high as that of untreated seeds. Of the two types of pelleted seeds we produced, the larger, with a long axis of 2.324 mm and a short axis of 2.096 mm, was suitable for mechanical seeding. The weight of 100 grains was 636.7 mg, or about 148 times that of untreated seeds. Both sowing depth and covering the soil surface with a perforated polyethylene film after sowing had significant effects (p<0.01) on the rate of germination and the size of rosette leaves in the first year of growth. Of the four combinations of 0 cm or 1 cm seeding depth and with or without the perforated polyethylene film, we found that a sowing depth of 0 cm and the use of film was most suitable: the number of seedlings was 3.6 times higher and the rosette leaf diameter was 1.3 times larger than in the least suitable condition of a sowing depth of 1 cm and without the film. In contrast, the yield in the second year of cultivation was highest, at 4.1 g per plant or 647.1 g/m², with the 1 cm sowing depth and without the film. The quality of the harvested product was evaluated according to the Japanese Pharmacopoeia 18th edition, and all test plots met the criteria for quality.