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  • If you're ever vacationing in the Flamingo section of Everglades National Park in Florida,

  • beware of the apples.

  • In fact, if you're pretty much anywhere from northern South America to Florida, including

  • the Caribbean and Galapagos Islands, and you see a tall tree growing near water with yellowish-greenish

  • crab apple-looking fruit, it's probably best to keep your distance.

  • The fruit might be delicious, but it could also be deadly.

  • Because that tree might be a Manchineelwhich, according to the folks at Guinness World Records,

  • is the world's most dangerous tree.

  • Every part of the Manchineel is toxic.

  • The sap in its wood and leaves can cause blindness and blistering, its fruit can cause boils

  • in the mouth and throat as well as severe intestinal damage that can kill you.

  • It's no wonder Spaniards gave it the nicknamela manzanilla de la muerte”, or "little

  • apple of death.”

  • The tree contains a number of toxins, but the worst is probably phorbol.

  • Or, I should say, phorbols. “Phorbolrefers to a family of related organic molecules

  • that have two terpene chemical groups.

  • And they're similar to compounds you have in your bodywhich is a bit of a problem.

  • See, phorbols mimic the action of diacylglycerol — a fatty molecule your body uses in a number

  • of ways, including to activate an enzyme called protein kinase C, or PKC for short.

  • PKC is a pretty big deal because it regulates things like cell growth and metabolic activity.

  • So when phorbols over activate PKC, cells will increase their expression of genes involved

  • in inflammation and cell death. This leads to a range of nasty effects like blistering

  • and ulcering.

  • Manchineels have phorbols everywhere, which is why you shouldn't touch any part of them.

  • Oh, and here's a not-so-fun fact: Phorbols are very soluble in water, so it's not a

  • good idea to stand under a Manchineel when it's raining, either. Which, you know, it

  • does in places like the Everglades. A lot.

  • What's not entirely clear is why this tree went so overkill on the toxicity.

  • It may be that, since the Manchineel typically grows in areas where there are lots of other

  • toxic plants, it has such overdeveloped defense mechanisms to stay competitive.

  • And it can get away with having toxic fruit because it doesn't need animals to spread its seeds.

  • It lives by the ocean, so its fruit can bob along on the waves to move to new lands.

  • Though, it may get more love from critters than you'd think.

  • Some reptiles seem to eat the fruit with no ill effects, and black spiny-tailed iguanas

  • will even live in the trees! How remains a mystery.

  • And even our species doesn't always keep away.

  • Because the trees live in places like Florida where there are a lot of strong windsand,

  • you know, hurricanes every so oftentheir wood is really hard.

  • So cabinet makers love it. Though, they have to carefully cut and dry the planks for several

  • days to let the phorbol-laced sap evaporate out.

  • And the trees aren't just hardtheir deep roots and thick branches help protect

  • coastlines from damaging winds and waves.

  • That means, while they might be toxic to touch, they help protect us and coastal ecosystems

  • during storms.

  • So if you do see a Manchineel while you're strolling along the beach, you can smile and

  • appreciate all that it's doing for the plants, animals, and people who live nearbyand

  • then give it a wide berth.

  • Thanks for watching this episode of SciShow! Fun, educational science videos like this

  • one are what we do, but we can't do it without the help of our patrons on Patreon.

  • If you want to learn more about joining our awesome community of patrons and how you can

  • help support the work we do, you can head on over to Patreon.com/SciShow.

  • And if you want to learn more about poisonous plants, you might enjoy our list of nine that

  • might be around your house right now! Some of them are quite surprising.

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