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Annals of Botany 74: 357-364, 1994
© 1994 Annals of Botany Company
Gynodioecy in Cirsium chikushiense Koidz. (Compositae)
Department of Biology, Faculty of Education, Kagoshima University, Kohrimoto, Kagoshima, 890, Japan
A study of the morphology and function of flowers in Cirsium chikushiense revealed that the species was distinctly gynodioecious. Self-incompatible hermaphrodite florets produced both seeds and pollen grains, while female ones produced seeds but no pollen grains at all. The degenerated stamens of females were not only smaller but also sometimes occurred at a lower position inside the floral tube than in hermaphrodites. The stigmata of females often developed more fully than those of hermaphrodites. The frequencies of female plants in natural populations varied from 15·5 to 50%. Almost all the pollinators stayed on both female and hermaphrodite heads only to collect nectar. The female plants of this species may be more specialized in their gender by saving the cost of not only pollen grains but also stamens, and may be maintained by sufficient pollinators in natural populations. This gynodioecy may provide an example of nuclear-cytoplasmic male sterility.Copyright 1994, 1999 Academic Press
Sex expression, gynodioecy, Cirsium chikushiense, Compositae, male sterility, degenerated stamen, female frequency