Floral syndrome and breeding system of Senna (Cassia) corymbosa

Abstract

Senna (Cassia) corymbosa is an ornamental plant with asymmetric flower in which petals and stamens are also involved in floral asymmetry. The pollen number of abaxial lateral stamen (AL), abaxial median stamen (AM) and middle stamen (MI) are descended in sequence. In field, the insects of visiting flowers are available and pollinators are essential to the pollination success of S. corymbosa. Bombidae was presumably the effective pollinators by buzzing pollination and wasp may be the potential pollinators. Pollen number and germination rate per type of stamen experiments supported the hypothesis of “division-of-labour” among stamens by Darwin. Both AL, AM and MI may afford food to visiting insects, while long stamens (including AL and AM) function as the “pollinating” stamens and the brownish yellow is presumably the effective color attractants to pollinators.

Key words: Senna, pollen, pollination, breeding system.