Feature of naturalized region of Papaver dubium (PAPAVERACEAE) in Japan−from the standpoint of seed germination characteristics

Abstract

The role of seed germination characteristics in facilitating the rapid acclimation of the exotic long-headed poppy (Papaver dubium) in Japan was assessed using indoor and outdoor cultivation experiments. Results of outdoor experiments showed that seeds sown in June germinated in the fall of the same year and the following spring. Indoor germination experiments, conducted using seeds stored under different temperatures and moisture conditions, revealed that seed germination rates were highest under the following conditions:(1) moist, warm conditions for 2 to 3 months followed by storage at 5°C, (2) moist, warm conditions for 3 months followed by storage under moist, cold conditions for half month to a month and then at 10∼20°C, and (3) storage for three months under varying temperature and moisture conditions. These outdoor and indoor germination experiments confirmed that seeds germinated under natural environmental conditions in the fall when temperatures decreased relative to the moist warm conditions of summer and in the subsequent spring when the temperatures increased after the cold winter months. Seed germination in seeds stored at high or room temperatures, under dry conditions for approximately three years, or under dark conditions, was relatively lower. Consequently, seeds that become buried in the ground are likely to remain dormant for extended periods of time. In addition, the optimal germination temperatures for the longheaded poppy observed in this study closely match the meteorological conditions of the numerous regions, both domestically and internationally, where this species is found.