27 January 2013
Another orchid on the kitchen table is blooming; this time it's the deliciously named cultivar Cycnoches cooperi 'Dark Chocolate' × 'Dark Fudge'. Thanks to these lovely little flowers, I'll now be able to voucher this specimen and include it in my phylogenetic work.
The interesting thing about this genus and its allied genera is that the flowers are unisexual and display sexual dimorphism where the characteristics of the male and female flowers are noticeably different. These here are the male flowers. You can tell by the narrow labellum at the top of the flower and the very long column below the labellum. It was that extraordinary column that gave the genus its common name swan orchids - there's a quite clever illustration at the bottom of the second to last page in this article that might help you visualize why the name is appropriate.
It has been suggested that plant vigor, amount of sunlight, or other environmental factors may lead to whether the plant invests its resources in presenting female flowers. A plant must be capable of supporting seed production if it is going to give up on the possibility of producing male flowers with relatively cheap pollen instead. Luckily for the swan orchids, the molecular "choices" that decide whether a flower is male or female do not decide the fate of all flowers for that year or season. Different inflorescences flowering at the same time can have opposite sex flowers as seen in figure 6 in this article (the photo by Katherine B. Gregg). Gregg's work in the 1970s is the last that I know of in Cycnoches to try and identify what combination of environmental patterns might be generating the plant's phenotypic plasticity. This kind of work has hit a new stride lately in population ecology (here's just one example in alligator weed). Might be an interesting project for someone to work on. And the study organisms aren't half bad to look at!