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5 Horrifying Ways Plants Can Fight Back

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Most people probably consider plants to be nothing more than a lovely green backdrop to their lives—one that is constantly being eaten by even the lowliest of animals. These people are unaware that plants have been slowly plotting their revenge. While you sleep, even our very food crops are subtly planning ways to seek payback! Here is a quick listing of just some of the ways we might expect to meet our ends at the leaves of these photosynthetic psychopaths.

1. Cyanide Poisoning

Over 3000 different plants—including apples, cassava, spinach, and lima beans—have evolved a defense that causes the animals that eat them to choke on hydrogen cyanide (HCN) [PDF]. This compound is synthesized by plants in an attempt to dissuade herbivores from munching down on them. During the process, called cyanogenesis, hydrogen cyanide is attached to sugar or fat molecules and eventually stored. When an animal eats a part of the plant containing these cyanide laced sugars (cyanogenic glycosides) or fats (cyanogenic lipids), they are broken down in the digestive tract, releasing the hydrogen cyanide which disrupts cellular respiration, the process from which we are able to, you know, continue living.

But how does the plant keep from poisoning itself? It compartmentalizes the poison in specialized cells which only release the poison after being ruptured. So an average plant cell sequence may go something like this: delicious, delicious, delicious, deadly poison, delicious. And the reason that we don't die from eating things like apples is that the concentration of cyanide is much lower than in plants like cassava, which need to be soaked in water or cooked in order to leach out the cyanide compounds! 

2. Giving You Immediate Heart Attacks

Some plants want to cut right to the chase. Why give you time to slowly die from cellular death like cyanide when they can just go for the heart of the matter, literally? Plants like foxglove contain incredibly potent toxins that can stop the heart dead in its tracks. Digitoxin, the cardiac glycoside responsible for the poisoning and named after the foxglove genus Digitalis, is fatal in excess of 10 milligrams. Toxins such as digitoxin are certainly a good way to ensure that even if a potential herbivore takes a nibble of you, chances are they won’t be doing so again—namely because they’ll be too busy convulsing on the ground, dying.

People have been accidentally poisoning themselves with foxglove for years; its leaves look remarkably similar to the leaves of comfrey (Symphytum spp.) which is commonly made into a soothing, healing tea. Below is a comparison of the two leaves. 

3. Injecting You With Horrifyingly Painful Neurotoxin

Some trees just want to see you suffer. The Stinging Tree of Australia (Dendrocnide moroides), or Gympie Gympie, is certainly one of them. This relatively innocuous looking plant is covered in countless microscopic hairs, all of which are loaded with an incredibly potent neurotoxin. The hollow hairs get easily stuck in skin on contact and deliver the neurotoxin, which causes intolerable pain and, sometimes, death—this according to Dutch Botanist H. J. Winkler, who recorded such an event in the 1920s after an associate was stung by the plant. 

How intense is the pain? It’s apparently akin to being burned alive while being stabbed and can apparently last for months after the initial sting. It turns out, plants can really hold a grudge. Here’s a video of an Australian biologist brushing the plant with the back of his finger for barely a second.

 

4. Covering You in Innumerable Biting, Swarming Ants

Wikimedia Commons

Just like humans, some plants have turned to hiring bodyguards in order to protect themselves. The bull-horn acacia (Acacia cornigera) has evolved a mutualistic relationship with the aptly named acacia ant (Pseudomyrmex ferruginea): In exchange for housing—inside of its giant thorns, which can house many ants each—and food (the plant feeds them through special nectaries and even by producing little bag-lunches for the ants in the form of fat and protein-packed Beltian bodies), the ants viciously defend the tree. 

If a herbivorous insect even so much as touches the tree, it is immediately descended upon by the ants, who will eat the intruder or throw it off the tree.  Even large animals such as humans will be given no mercy by the ants, who will swarm and bite in order to defend their precious all-providing tree. In fact, many bull-horn acacias have reduced pollination rates as compared to other plants as even beneficial pollinating insects can barely approach the tree without having a hurricane of ants sweep them to their deaths!

5. Summoning Deadly Wasps from the Heavens

When you think of corn (Zea mays), you may think of warm summers, grilling with your family, and enjoying the ears at your leisure, slathered in butter. Rarely do people think of corn as a capable arcane wizard of a plant that can call down a torrent of wasps to annihilate would-be murderers. 

Corn, as well as many other plants, produces what are referred to as “green leaf volatile compounds” when its leaves are chewed on. These compounds are a cocktail of various chemicals, including terpenoids and phenolics, that are incredibly attractive to parasitic wasps. These wasps fly to the plant that is being eaten, find the culprits and, depending on the species, employ a few different protection strategies: some wasps, like digger wasps (genus Sphex), will actually pick up the host and put it somewhere else. Other wasps will lay eggs in the creature munching on the plant; those eggs hatch a la the Xenomorphs from Alien, often chewing their way out of the host’s body cavity within a day or two. 

This sounds like a long time if you're being eaten, but it takes a while for caterpillars or other insects to completely destroy a corn plant. Generally, the host is dying or near dead by the time the larvae emerge. So the next time you pick a fresh ear of corn, make sure you leave as quickly as possible—the wasps are probably already en route.

Additional Source: Lambers, H., Chapin F.S., Pons, T.L., Plant Physiological Ecology, Second Edition, Springer Science+Business Media, LLC, 2008, New York.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
May 21, 2017
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iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

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May 23, 2017
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