Non-functional flowers in Catasetum orchids (Catasetinae, Orchidaceae)

Abstract

ROMERO, G. A., 1992. Non-functional flowers in Catasetum orchids (Catasetinae, Orchidaceae). Plants of the genus Catasetum generally produce unisexual, dimorphic flowers but occasionally bear intermediate, polymorphic flowers. Staminate (male) flowers are commonly produced both in cultivation and in nature. Within the genus, the morphology, texture, resupination, and colour of male flowers are extremely variable. Pistillate (female) flowers, in contrast, are rarely produced in cultivation and in nature and have relatively constant morphology, texture, resupination and colour. Intermediate, polymorphic flowers are extremely rare, ranging in morphology from male-like to female-like, often combining characters of both. Some are bilaterally half male and half female. Intermediate flowers have previously been regarded as functionally hermaphroditic but evidence presented here shows that in Catasetum male and female functions appear to be mutually exclusive. Intermediate flowers that approach the morphology of female flowers may bear seeds but do not have functional pollinaria; those that approach male flower morphology do not have functional stigmas and seldom have functional pollinaria. The vast majority of Catasetum intermediate flowers are sterile. The absence of truly hermaphroditic flowers in Catasetum is important in the interpretation of evidence for gender choice in this genus, as flowers and/or plants can be unequivocally scored as either functionally male or female.