Spring-Loaded Hood Orchids
Some orchids of the genus Pterostylis have adopted rapid plant movement as a method of ensuring pollination.
Male fungus gnats are attracted to pheromones exuded by the flower and try to copulate with the dark, furry structure known as the labellum. The labellum is attached to a sensitive elastic strap that flips upwards in response to disturbance.
If a gnat lands on the labellum, the whole surface springs back and traps the pollinator in the hood. To escape, the insect must crawl through a small opening in the hood, brushing against the orchid’s pollinia in the process. These sticky packets of pollen adhere to the insects back.
The insect, now carrying pollen, visits a new flower and goes through the ordeal again. This time, the pollen on the insect’s back brushes past the new flower’s stigma while the pollinator escapes, which fertilises the flower.
(Pterostylis longifolia shown)