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  • 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 aroundwhich 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. Theyre 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.

  • Theyre 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 sayingcome 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. Theyre trying

  • to attract parasitic wasps.

  • These wasps are a lot different from the yellow jackets invading your summer picnic. For one

  • thing, theyre tiny. They also happen to lay their eggs inside caterpillars.

  • The eggs hatch into larvae while theyre 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 membership. Check out audible.com/scishow

  • where you can choose from over 180,000 audio programs and titles like Wicked Plants by

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  • title today.

Plants are a lot like animals, in the sense that they have to get nutrients to grow, fight

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植物がボディガードを引き寄せる方法 (How Plants Attract Bodyguards)

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    SylviaQQ に公開 2021 年 01 月 14 日
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