Field of Science

Rainforest Field Trip - Corkscrew Flower

This largish, coiled flower (3") reminds many people of a seashell, but this ones smells pretty good. Most of my students guess this is some type of orchid, but the coiled shape fools everyone pretty well and even though most of you would think you knew the family pretty well, you might not figure out that this is a legume, a bean. Now the standard faboid bean flower has 5 petals: an upright standard, a pair of laterals, and two lower petals forming a keel within which the 10 anthers and pistil are located. In many cases a pollinator's weight causes the keel to shift downward so that the stamens or stigma make contact with the pollinator's body. Actually this tropical bean flower (Vigna) works the same way, sort of. The standard petal makes the coil (to the left), and the "laterals" are skewed to the top and bottom (lavendar ones), and the keel within is a long narrow coil. The bottom lateral petal forms the landing pad and weight upon this petal shifts the corolla such that long, coiled style and stigma within the keel push pollen out of the tip of the long, coiled keel, or once the pollen is depleted, just the stigma itself emerges several mm. One of the problems in a diverse ecosystem like a rain forest is having enough pollinators to go around, so to use the same pollinator without getting incompatible pollen clogging your stigma some flowers apply pollen to the top and some to the bottom of a pollinator allowing two different plants to share the same pollinator. Coiled flowers like this legume go one step further in dealing with the dorso-ventral biology of animals. This flower is asymmetrical forcing the pollinator to enter the flower from just one side and the pollen is delivered to and picked up from the left side of the pollinator. If you know how you can make this flower work by just pushing down gently on the landing pad petal. Go ahead, try it!

1 comment:

Greensparrow said...

So cool! I've seen the flowers before, but never could figure out how they worked the whole pollination thing.