Characteristics of the Falling Speed of Japanese Orchid Seeds

Orchid seeds, which are produced in abundance, are particularly small and light. Some orchid species are anemochorous, i.e., bear seeds that are dispersed by wind. To characterize the seeds of Japanese orchids, we measured the size of seeds and embryos of 68 Japanese orchid species. Most orchid seeds had a length of 0.3 to 2 mm and a width of 0.07 to 0.2 mm. Embryo length and width were 0.1 to 0.3 mm and 0.04 to 0.2 mm, respectively. Twenty-seven orchid species produced 1000 to 350000 seeds per pod. Speeds of fall of 34 Japanese orchid species were examined in order to obtain insight into their seed dispersal ability. Falling speeds ranged from 4 to 30 cm/s. These results strongly suggest that seeds of Japanese orchids are also dispersed by wind and thus that most Japanese orchids are anemochorous species.