Season 7 Episode 15 | 3m 57s | Video has closed captioning.
Cape sundews are carnivorous plants that grow in bogs, where they don't have access to many nutrients. So they exude sweet, shimmering droplets from their tentacles to lure in unsuspecting insects. Once their prey is hopelessly stuck, they wrap it up and dissolve it for a tasty meal.
Aired: 08/06/20
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You’ve probably heard of the infamous Venus fly trap ... ... or the elegant pitcher plant.
Sundews are their sticky, shimmering relative.
There are hundreds of species.
Some of them small as a pea, others with towering branches the length of your arm.
They’re often found in bogs with nutrient-poor soil where only some plants can thrive.
But they need more nitrogen and phosphorus than they can find in this meager soil.
So our carnivorous friends evolved a resourceful way to bring a little life into their diet.
Each leaf is studded with red, hair-like tentacles that secrete dew drops from their round glands.
Those glistening droplets are made of water and complex sugars.
They lure in insects – like this unfortunate weevil – with their sweet aroma and taste.
But before long, the weevil gets hopelessly trapped in this super sticky substance.
Sessile glands at the base of the tentacles release digestive enzymes into the prey.
Some sundews, like this forked variety, dissolve their meals on the spot.
But the Cape sundew goes even further.
Over several hours, it tightly grips its meal with its leaves.
By completely enveloping its prey, the sundew can extract even more nutrients.
Cape sundews bend the very idea of how we think plants should behave.
They not only move their tentacles, but they sense prey with them, too.
Incredibly, they seem to be able to tell what’s alive – like this fly – and what’s not, like this leaf.
Just a tiny stimulus can set the sundew in motion.
Moving in response to touch like this is called thigmotropism.
While plants don’t have brains or neurons like we do, they do use electrical signals just like our nervous systems.
Scientists call these signals “action potentials.” They guide the tentacles’ graceful and deadly grasp.
It’s possible that sundews can also detect whether they’ve trapped something that’s nutritious or not.
That one got lucky.
For the unlucky ones, all that’s left is an empty exoskeleton.
When a sundew’s had its fill, it will slowly unfurl again, patiently waiting for its next meal.
