This Orchid Has a Spring-Loaded Propulsion System
Catasetum tenebrosum orchid photo credit: Arne and Bent Larsen, CC BY-SA 2.5 DK via Wikimedia Commons
By now, no weird orchid fact should be surprising. Given that over 28,000 species of orchids exist, and given the staggering diversity of those plants, perhaps we should assume that orchids can do just about anything (a career in politics, perhaps?) And yet, I continue to learn things about them that make my jaw drop.
Case in point: male catasetum orchid flowers eject pollen sacs with surprising speed and force when touched by a potential pollinator. There are 166 species in the genus catasetum, and most have this capability. Many people have captured this process in video. Here’s one, complete with slow-motion, from the Huntington Library, art collection, and botanical gardens:
(that blurry yellow thing is the pollen sac!)
In the above video, a human triggers the launch mechanism of a Catasetum sanguineum. The flower’s anther generates pollen, which forms two sacs of pollen grains called pollinium. The pollinium connect to the flower’s column or main stem via a pedicel, which is the key piece. The pedicel is like spring on a mouse-trap—triggering it sets off the whole thing.
The pedicel stores potential energy by coiling up and then being held in place by the flower’s hooked and sticky rostellum, which is similar to a mouse trap’s down-bar. When an insect (or finger) touches the flower’s antennae, the rostellum breaks and the pedicel releases and launches the pollen sac. The pollen sac then sticks to an insect—in this case, a Euglossine bee attracted by the scent of male flowers—which buzzes from flower to flower and facilitates cross-pollination.
Image credit: https://cronodon.com/BioTech/orchids.html
Catasetums are epiphytic, deciduous orchids that experience growing periods and dormant periods. They store water and energy in pseudobulbs, which allows them to rest during the dry season. They’re native to tropical areas, including Central and South American and the West Indies, and prefer temperatures of around 80 F during their growing season.
Charles Darwin was a particular fan of catasetum orchids and he wrote about them in his book Fertilisation of Orchids. He described this amazing pollen sac ejection system only to face ridicule from some scientists who couldn’t believe his descriptions.
Botanists were perplexed by catasetums because of how different the male and female flowers look—botanists and taxonomists thought they might be different species entirely. But Darwin was able to figure out that the male and female flowers come from the same plant, and that the plant’s growing environment determines whether it grows a male or female flower. That’s unusual, since the majority of orchids have both male and female organs.
Catasetum barbatum photo credit: Stefano, CC BY-NC-SA 2.0 via Flickr
Orchids may not have opposable thumbs, but catasetum orchids come with their own mini catapults. They’ve also mastered free transit, as the pollen sacs stick tight to the pollinating bees. What will they think of next?!
