How Plants Attract Bodyguards


Plants are a lot like animals, in the sense
that they have to get nutrients to grow, fight off anything that wants to eat them, and reproduce. But, unlike most animals, plants can’t just
get up and move around… which is why some of them put out nectar to recruit bodyguards. Lots of flowering plants produce sugary nectar,
which attracts pollinators like birds, bats, and insects. They take the pollen with them
to the next flower, helping the plant reproduce. But a few plants have evolved a completely
separate source of nectar. They’re known as extrafloral nectaries, special structures
outside of the flower that produce a liquid cocktail of sugars and amino acids — a lot
like the nectar inside flowers, just in a more strategic place. As the nectar-eaters defend their source of
food, the plant ends up with bodyguards. Nectars — both the floral and the extrafloral
kind — are meant to attract and reward animals, creating what’s called a mutualistic relationship. The animals benefit from the nectar — since
they get food — and the plant gets either pollinators or protection. It’s a win-win. For instance, in Inga plants in tropical rainforests,
ants will get rid of other, plant-eating insects. These outside nectaries are rich in carbohydrates,
like sucrose and glucose, as well as proteins and amino acids — all important nutrients
for the ants. In exchange for the food, the ants protect
the plants from invaders like caterpillars. They’re pretty good at it, too — studies
have shown that leaves without ants get much more damaged than leaves that do have ants. And, when a plant eater comes to munch on
its leaves, the Inga can make extra nectar as a bonus incentive for the ants. The plant’s basically saying “come help,
I’m under attack! Here, take more sugar!” Then there’s the Passion flower, a North
American plant that has extrafloral nectaries at the base of each leaf and under the flower
bud. The passion flower already has poisonous chemicals
in its leaves. But some species of butterfly have evolved an immunity to the toxic leaves,
and recruiting ants gives the flower another line of defense. In the 1980s, a group of researchers removed
the outside sources of nectar from some passion flowers. They found that those plants had
fewer ants around them, were attacked more, and made less fruit. Even cotton plants have them — though they
aren’t looking for ants. They’re trying to attract parasitic wasps. These wasps are a lot different from the yellow
jackets invading your summer picnic. For one thing, they’re tiny. They also happen to
lay their eggs inside caterpillars. The eggs hatch into larvae while they’re
still in the caterpillar and start to eat it, eventually clawing their way out through
its skin. All while it’s still alive. Then they take over the caterpillar’s mind,
forcing it to protect them as they keep growing. Once they fly away, the caterpillar starves
to death. As you can probably imagine, it’s an effective
way to kill a caterpillar, which is why some cotton farmers use these wasps as a natural
pesticide. The cotton plant sets out its nectar as a
food source for the mini wasps, and in return for the sugary snack, the parasitic wasps
stick around and take over the caterpillars. But nectar’s good for defending against
more than just insects. According to a study published in 2009 in
The Plant Journal, it also has compounds that protect the plant from invading viruses, bacteria,
and fungi. For example, the nectar of certain Acacia
plants contains proteins called chitinases that stop invading fungi. Meaning that sometimes the extrafloral nectar
itself is a kind of bodyguard. That nectar doesn’t come cheap, though,
energy-wise. To make it, the plant has to use energy it could otherwise be using for
things like growth and reproduction. But for a lot of plants, it’s worth setting
out a nectar pot for a little extra security. Thanks for watching this episode of SciShow,
sponsored by Audible. Right now, Audible’s offering SciShow viewers a free 30-day trial
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71 thoughts on “How Plants Attract Bodyguards

  1. But what about root exudates?! Helps the soil microbes to cycle organic material to release nutrients. Want to know something even better? There is evidence that some plant can absorb whole bacteria as a source of nutrients ?

  2. QQ: How do electronic calculators work? (And do they work the same way on phones, or do phones just automatically look the answers up?)

  3. Insects like mealy bugs also produce a kind of nectar that attracts ants to defend them against predators like the mealy bug destroyer while they feast on the plant (usually citrus). So the bodyguard trick can cut both ways, depending on who's doing the bribing.

  4. So the protectors get to eat the nectar and whatever other insects happen to feeding on that plant's body, giving them no reason to feed on the plant itself. Neat.

  5. I was wondering about the science behind "talents", why are some people so much better than others at something even when, at times the same effort was put in, thinking of my own "talents" (drawing and artistic endeavours, as well as academic intelligence in maths and science but mostly drawing). I was disliked people saying I was "talented" because I put effort into things and usually have the assumption people can do the same (given drawing is the use of lines, curves and geometry) and usually can, but with a lot more effort. I really wonder why, (I assume it is to do with hand eye coordination, or whatever fits a given activity) but I don't like assuming.

  6. I want to know how fish hear underwater. There is no videos on this topic and I could only find literature in encyclopedias and biology books.

  7. Wait, wait…go back to the part where THE WASP LARVAE TAKE OVER THE CATERPILLAR'S MIND?! Can we have an episode on THAT?!

  8. so wait…. plants basically lure wasps to kill insects and benefit from the process, they make ants want sugar so much they kill insects that'll try to eat thr plant, hence again benifit from murder….are plants actually evil geniuses?

  9. I wonder if the people on the walking dead would be able to wipe out the zombie population with the right insect/worm/parasite. I'm sure they could find some flies to do it.

  10. SciShow, can you guys slow down the speech monologue used in videos? At some points, you're talking so fast, I'm concentrating more on deciphering the really fast speech versus understanding the information.

    Also, the jump cuts don't help much if the natural speech patterns are interrupted, and causes monologues to turn into even larger blocks of monologues.

    Otherwise, I love everything you do!

  11. You can't beat a human bodyguard, some plants are special enough they've been selected to grow on a space station. You hear that you stubborn dandelions? Get outta my yard dandelions >.<

  12. This isn’t really related to plants but it’s about bugs that live ON plants, aphids produce a byproduct called honey dew (it’s… really sugary poop, don’t eat it), which larger bugs eat. This attracts things like bees and ants which in turn, scare away any ladybugs on the plant, the natural predator of aphids. They literally poop to save their own lives.

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