Sex expression and reproductive biology of Stachyurus praecox (Stachyuraceae)
2007
Abe, T.(Forestry and Forest Products Research Inst., Tsukuba, Ibaraki (Japan))
Sex expression, sexual differences, flower visitors, and fruit set of Stachyurus praecox were examined in forest edges of Mt. Tsukuba for two years. Floral morphology, sexual organs (ovule and pollen), and fruit set suggested that S. praecox was gynodioectic. Sex change was not observed for two years. Significant sexual differences were observed in the number of flowers per inflorescences and fruit set. Despite the existence of ovules, fruit set of hermaphrodite flowers was very rare (nearly 0.0%) and was not increased by hand-pollination. Thus, the hermaphroditic flowers seemed to contribute mostly as male and this species is considered to be functionally dioecious. In addition, the rare existence of intermediate inflorescence containing hermaphroditic flowers and female flowers implied that the sex expression of S. praecox was instable. About 35% of female flowers set fruit in both years, and hand-pollination did not increase the amount of fruit set. Frequent flower visitors such as hover flies and small solitary bees were likely to be effective pollinators for S. praecox flowering in early spring in sunny forest edges.
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