Fluctuation of 20-hydroxyecdysone in Individual Organs of Achyranthes japonica during Reproductive Growth Stage and Its Accumulation into Seed

To better understand 20-hydroxyecdysone (20E) fluctuation and accumulation in perennial plant, 20E concentration in individual organs of Achyranthes japonica during reproductive growth stage were analyzed by high performance liquid chromatography (HPLC). Concentrations of 20E in root and floral part were much higher than those in stem and leaf during reproductive growth stage and rapidly increased from flowering stage in August to seed-setting stage in October, and thereafter decreased at the stage of seed maturing in November. In contrast, the 20E concentrations in stem and leaf gradually decreased during reproductive growth. In the analysis of detailed fluctuation of 20E in floral part, the 20E concentration was highest in the seed at the early stage of seed development, compared to flower, peduncle, seed coat, and/or seed in other growth stages, and decreased during seed maturation. The accumulation of 20E in reproductive organs, especially seed and root, suggests that 20E has a defensive role for protection of especially newly developing organs against phytophagous insects.