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This Plant Bleeds Sweet Nectar To Recruit Ant Bodyguards

A bittersweet nightshade plant, Solanum dulcamara.
A bittersweet nightshade plant, Solanum dulcamara.
Photograph by Joel Sartore

Six years ago, Anke Steppuhn noticed that the bittersweet nightshade, when attacked by slugs and insects in a greenhouse, would bleed. Small droplets would exude from the wounds of its part-eaten leaves. At the same time, Steppuhn and her colleagues saw that the wild plants were often covered in ants.

These facts are connected. Steppuhn’s team from the Free University of Berlin, including student Tobias Lortzing, have since discovered that the droplets are a kind of sugary nectar, which the beleagured nightshade uses to summon ants. The ants, in return for their sweet meals, attack the pests that are destroying the plant. And this discovery provides important clues about the evolution of more intimate partnerships between ants and plants.

Acacia trees, for example, are masters at recruiting ant bodyguards. The insects protect the trees from plant-eaters and even prune back invading vines. In return the trees provide them with shelter in the form of swollen thorns, snack stations that look like orange berries, and drinks in the form of nectar. The latter come from small green lumps called extrafloral nectaries, which the ants sip from.

Some 4,000 species of plants have extrafloral nectaries, which vary considerably in their shape. Some are obvious structures, like those of the acacia. Others are mere pits or hollows. But whatever their form, their benefits are invaluable. They are not only ant rewards, but also ant concentrators.

“Ants often appear to be whimsically inefficient plant defence agents,” says Elizabeth Pringle from the Max Planck Institute for Chemical Ecology. “They wander to and fro, haphazardly nipping at anything that happens to be in their way, which gives plenty of time for something with a hard exoskeleton and wings, like an adult flea beetle, to escape and happily land somewhere else to feed. But concentrate lots of ants around a sugar source, and pretty soon nothing soft and slow stands a chance. This is the value of extrafloral nectaries.”

The bittersweet nightshade’s oozing droplets have almost all the characteristics of extrafloral nectaries. It’s a sweet liquid, obviously. But Lortzing showed that it’s not just fluid that passively leaks from a damaged leaf. When he cut the nightshade with a clean scalpel, the nectar droplets didn’t appear. They did emerge, however, if Lortzing first coated his scalpel in jasmonic acid—a hormone that plants release upon insect attack.

Sweet nectar oozes from a wounded bittersweet nightshade.
Sweet nectar oozes from a wounded bittersweet nightshade.
Photograph by Tobias Lortzing

He also showed that the nectar is chemically distinct from the plant’s actual sap—full of sweet sucrose, and deficient in almost everything else. Clearly, it is actively produced and secreted by the plant.


To find out, the team added droplets of either sucrose or water to wild undamaged nightshades. After a month, they saw that the sucrose-treated plants were patrolled by more ants, and had suffered half as much damage to their leaves. To their surprise, the ants even seemed to protect the nightshades against slugs. That’s new. Ants have been known to defend plants against other insects and mammals, but never before slugs or snails.

More bizarrely, the ants didn’t seem to attack adult flea beetles—the nightshade’s greatest enemies. They seemed like poor defenders, until Steppuhn’s team realised that the ants were focused not on the beetle adults, but on their larvae. The larvae hatch from eggs in the soil, climb up the nightshade’s shoots, and bury themselves in its stem.

Ants will pick up the larvae and carry them into their nests, never to be seen again. The ants might ignore the adults, but they stop the next beetle generation from causing even greater harm.

So, the nectar droplets, being actively produced, chemically distinct, and efficient at summoning guardian ants, are very much like the extrafloral nectaries of other plants. The only difference is that they’re not associated with any specific structure—no obvious lump or pit. It’s the “most primitive extrafloral nectary that has been discovered so far and shows how little is needed to make a functioning nectary,” says Martin Heil from CINESTAV in Mexico.

Although such structures are common throughout the plant world, every group with nectary-bearing species also has nectary-less members. “This means that extrafloral nectaries appear and disappear quickly, in evolutionary terms,” says Heil. And Steppuhn’s discovery “helps us understand why and how these nectaries can evolve out of nowhere.”

Perhaps, at first, fluids that passively leak from wounds are visited by ants. Gradually, plants evolve to recruit the ants more effectively by controlling those leaks and tweaking the liquids that emerge, as the nightshade has done. Eventually, they develop specialised structures.

But nectaries are lost so frequently among plant families that they clearly incur some cost, says Pringle. It takes a lot of up-front investment to build the dedicated structures and to keep them constantly brimming with nectar. By contrast, the nightshade’s droplets show that plants can summon ants in a more ad hoc and less effortful way.

Whether plants go for that cheaper option, or head towards full-blown nectaries, probably depends on how badly they’re threatened by plant-eaters, how effective ants are, and how much energy it takes to summon and reward them. Nothing in nature comes for free, and evolution is the ultimate arbiter of costs and benefits.

Getting to the Root of How Earth’s Massive Coal Seams Formed

Close-up of a lycopsid tree. Did fungus break down these plants? Image from Wikipedia.
Close-up of a lycopsid tree. Did fungus break down these plants? Image from Wikipedia.

Writing about science is a tightrope walk. You can practice as much as you want, and during preparation you have lifelines in the form of editors and experts you can phone for answers, but in the end it’s just you out there, trying to toe the line suspended between attention and accuracy. Eyes are on you for any misstep, and even a perfect performance comes with an often-unrecognized risk. That’s because science is a process, not a static collection of facts, and in an instant a new discovery or study can make the rope vanish beneath your feet.

A few months back my Phenomena neighbor Robert Krulwich wrote a post titled “The Fantastically Strange Origin of Most Coal on Earth.” It’s a lovely little story, all about how a delay in microbial evolution allowed the vast forests of over 300-million-years-ago to become compressed into the fossil fuels we rely on. “[W]hen those trees died,” Krulwich writes, “the bacteria, fungi, and other microbes that today would have chewed the dead wood into smaller and smaller bits were missing.”

Paleontologists call this the “lag hypothesis.” And it turns out to be wrong.

Back in March, about two months after Krulwich’s post went up, Stanford University geoscientist Matthew Nelsen and colleagues published a paper in PNAS that set the record straight in the very title: “Delayed fungal evolution did not cause the Paleozoic peak in coal production.” What seemed like a neatly-solved question once again turned into a conundrum.

The key to the puzzle is lignin. This is the sturdy stuff that often gives bark, wood, and even the cell walls of many plants their resilience. And in the thick forests of the Carboniferous, over 300 million years ago, lignin was supposed to be the stuff that microoganisms and fungi just couldn’t chew up. With no decomposers up to the task, the enormous trees of the time and other plant material piled up for burial rather than breaking down.

A 19th century rendition of a Carboniferous forest. Source.
A 19th century rendition of a Carboniferous forest. Source.

Yet new discoveries have totally reversed what paleontologists expected of those primordial forests. The bulk of the great Carboniferous swamp biomass consisted of trees called lycopsids, Nelsen and colleagues write, but up to 80% of these plants was made of a kind of bark that has no modern equivalent. In other words, these trees did not rely on lignin to support themselves.

And it gets better. “Carboniferous fossils provide direct evidence that fungi were taxonomically and ecologically diverse,” Nelsen and coauthors point out, and paleontologists have already uncovered Carboniferous wood “infiltrated with fungi and possessing damage consistent with white rot decay or other forms of fungal degradation of lignified tissue.”

The lag was in our understanding, not fungus evolution. Lignin wasn’t as critical as had been thought, and, even then, fungus and other decomposers were still capable of busting up the material. And this makes the vast coal seams created by these forests even stranger. If not a reprieve from becoming compost, what could have made such a glut of fossil fuels? The answer, Nelsen and colleagues suggest, probably has to do more with how those forests became buried.

Carboniferous forests were incredibly productive, throwing up plant life faster than the dead plants could decay, creating a literal logjam of organic material in the hot, humid habitats. This happened in a glacial world, but as those stores of ice melted the thick tangles of slowly-decaying plants were buried and eventually compacted down. The Earth’s crust had its own role to play, too. The sweltering forests grew in areas of the planet that were shunted beneath the surface as Pangaea coalesced, the movement of the Earth providing the geological forces necessary to create the fuel for the Industrial Revolution and the climate change we’ve brought upon ourselves.


Nelsen, M., DiMichele, W., Peters, S., Boyce, C. 2016. Delayed fungal evolution did not cause the Paleozoic peak in coal production. PNAS. doi: 10.1073/pnas.1517943113

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The Sneaky Life of the World’s Most Mysterious Plant

It looks so ordinary, this vine. But it’s not. It is, arguably, the most mysteriously talented, most surprising plant in the world.

Photograph Courtesy of Ernesto Gianoli
Photograph Courtesy of Ernesto Gianoli

It’s called Boquila trifoliolata, and it lives in the temperate rain forests of Chile and Argentina. It does what most vines do—it crawls across the forest floor, spirals up, and hangs onto host plants. Nothing unusual about that.

Drawing by Robert Krulwich
Drawing by Robert Krulwich


But one day a few years ago, Ernesto Gianoli, a plant scientist, came upon a Boquila trifoliolata while walking with a student in the Chilean woods. They stopped, looked, and “then it happened,” Gianoli says. On the forest floor, they could see that the vine’s leaves looked like this, kind of stumpy and roundish:

Drawing by Robert Krulwich
Drawing by Robert Krulwich

But once the vine climbed up onto a host tree, its leaves changed shape. Now they looked like this—much longer and narrower:

Drawing by Robert Krulwich
Drawing by Robert Krulwich


Both leaves came off of the same vine, but when the vine changed hosts, its newer, longer leaves matched its new surroundings. In Gianoli’s photograph below, the vine leaves are marked “V” and the tree leaves “T,” for “tree.” As you can see, it’s hard to tell them apart.

Photograph Courtesy of Ernesto Gianoli
Photograph Courtesy of Ernesto Gianoli

It’s almost as if the plant is camouflaging itself, changing shape to resemble its host.

As Gianoli walked along, he kept an eye out for Boquila vines climbing through the forest, grabbing onto tree after bush after tree, and it happened again! What he saw he found “astonishing.”

Photograph Courtesy of Ernesto Gianoli
Photograph Courtesy of Ernesto Gianoli

In this photo, the vine is on a different tree, and this time the tree’s leaves (marked “T”) are rounder, more like flower petals. And the vine (the leaf marked “V”)? Its leaves are now roundish too!

Woody Allen once made a film called Zelig, about a guy who takes on the characteristics of whomever he’s standing next to. The more Gianoli looked, the more Zelig-like this vine became, morphing over and over to look like one different host after another.

As my blog-buddy Ed Yong described it in 2014, when he wrote about this same plant, it has all kinds of moves: “Its versatile leaves can change their size, shape, color, orientation, even the vein patterns to match the surrounding foliage.”

On this tree, for instance …

Photograph Courtesy of Ernesto Gianoli
Photograph Courtesy of Ernesto Gianoli

… the tree leaf is jagged-edged, like a saw blade. (We’ve marked it with a “T.”) Our vine tries to create a zig-zag border (see the leaf marked “V”) and sort of pulls it off. Here’s a case, said Gianoli to Yong, “where Boquila ‘did her best’ and attained some resemblance but did not really meet the goal.”

Good try, though. It’s a crafty little vegetable.

But Why? How Does Mimicry Help This Vine?

The probable answer is that it keeps it from being eaten.

The forest is full of leaf-eaters. Imagine a hungry caterpillar wandering up to a tree:

Drawing by Robert Krulwich
Drawing by Robert Krulwich

It loves eating leaves. It might find vine leaves extra tasty. But if our vine is hiding among the many, many leaves of the tree, each vine leaf has a smaller chance of being chewed on.

Or maybe the vine is assuming the shape of leaves that are toxic to the caterpillar. This is called Batesian mimicry, when a harmless species tries to look like a very bad meal.

Whatever the reason, mimicry seems to work. Gianoli and his co-author, Fernando Carrasco-Urra, reported that when the vine is mimicking its neighbors higher up, it gets chewed on less. On the ground, it gets eaten more. But what’s really intriguing about this vine is how it does what it does: It’s been called the “stealth vine” because, like the classified American spy plane, its inner workings are still a secret.

Learning Its Secret…

No plant known to science has been able to mimic a variety of neighbors. There are some—orchids for example—that can copy other flowers, but their range is limited to one or two types. Boquila feels more like a cuttlefish or an octopus; it can morph into at least eight basic shapes. When it glides up a bush or tree that it’s never encountered before, it can still mimic what’s near.

And that’s the wildest part: It doesn’t have to touch what it copies. It only has to be nearby. Most mimicry in the animal kingdom involves physical contact. But this plant can hang—literally hang—alongside a host tree, with empty space between it and its model, and, with no eyes, nose, mouth, or brain, it can “see” its neighbor and copy what it has “seen.”

How Does It Do This?

Gianoli and Carrasco-Urra think perhaps something is going on in the space between the two plants. They imagine that the bush or tree may be emitting airborne chemicals (volatiles) that drift across, like so …

Gif by Robert Krulwich
Gif by Robert Krulwich

… and can be sensed by the vine. How the vine translates chemicals into shapes and then into self-sculpture nobody knows. The signal could be written in light, in scents, or perhaps in a form of gene transfer. It’s a mystery.

“It’s hard for us to grasp that there are … ‘scents’ that we cannot smell, but which plants, noseless and brainless, can,” writes science journalist Richard Mabey in his new book The Cabaret of Plants. It’s against the rules to call a plant “smart” the way we might call a dolphin smart; brainless beings aren’t properly called intelligent. Intellect, we like to think, requires a nervous system like our own, which is an animal thing, except that, as Mabey writes, “[I]n being able to cope with unfamiliar situations, [this vine] is demonstrating the first principle of intelligence.”

Hmmm. A knock, knock, knocking on the animal kingdom’s door? Or do plants have their own secret ways of reckoning, totally unknown to us? If Boquila can do this, surely there are others.

This little vine is sitting on a gigantic secret. I can’t wait to find out what it’s doing, because whatever it is, it’s whispering that plants are far more talented than we’d ever imagined.

To find out more about Boquila trifoliolata, you can start where I did, with Ed Yong’s wonderful post from a couple of years ago, then go on to geneticist Jerry Coyne’s post, which asks a barrage of provocative and stimulating questions, and finish up with Richard Mabey’s short essay in The Cabaret of Plants. Or you can check out the science paper from Gianoli and Carrasco-Urra that started it all.

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Does the Loneliest Plant in the World Need Help?

One day in 1895, while walking through the Ngoye Forest in Zululand, southern Africa, a botanist with the oh-so-suitable name of John Medley Wood caught sight of a tree. It sat on a steep slope at the edge of the woods and looked quite unlike its neighbors, with a fattish trunk (actually it had two trunks) and what seemed like a splash of palm fronds on top.

It’s now called E. woodii, in Wood’s honor. It is a cycad. Cycads are a very old order of tree. They’ve been on the planet for roughly 280 million years, but this one is special—in a bite-your-lip kind of way. Richard Fortey, one of the world’s great biologists, calls it “Surely … the most solitary organism in the world.”

Illustration by Stocktrek Images, Inc., Alamy Stock Photo
Illustration by Stocktrek Images, Inc., Alamy Stock Photo

What Wood found may be the last surviving wild example of an ancient species of cycad, which stretches back in an unbroken line to the age of the dinosaurs. Now it’s all by itself, writes Fortey, “growing older, alone, and fated to have no successors. Nobody knows how long it will live.”

Unless there’s a twist ending. And thereby hangs a tale:

Wikimedia Commons
Wikimedia Commons

In the 1890s Wood, who made his living collecting rare plants (he directed a botanical garden in Durban), had some of this odd tree’s stems pulled up and removed and, in 1903, sent one of them to London, where it sat in a box in the Palm House at the Royal Botanical Gardens at Kew. It was a very long sit, being on display—by itself—for the entire 20th century. It’s still there.

Two hundred million years ago, cycads were everywhere. The giant continent that includes today’s Greenland and Antarctica were covered with them. Pterodactyls flew between them. Big dinosaurs munched on them. During the Jurassic period, small, stumpy, palm-looking trees made up about 20 percent of the world’s plants.

Illustration by Stocktrek Images, Inc., Alamy
Illustration by Stocktrek Images, Inc., Alamy

Somehow these E. woodii survived the catastrophe that wiped out the dinosaurs, got through five different ice ages, learned to live with bigger, newer trees—conifers and leaf bearers, followed by a profusion of fruiting and flowering plants—then got pushed into smaller, then even smaller, spaces until there were merely tens of thousands, then thousands, then hundreds, and then, for this particular species, perhaps, just this one.

The problem is that these trees cannot fertilize themselves. Some plants contain male and female parts on the same individual. Not E. woodii. It is, as the botanists say, dioecious. It needs a mate.

Photograph Courtesy of RBG Kew
Encephalartos woodii, Photograph Courtesy of Royal Botanic Gardens, Kew.

When a cycad is ready to reproduce, it grows a large colorful cone, rich with pollen or seed. It signals its readiness by radiating heat or sending out attractive odors to pollinators, who travel back and forth. Once fertilized, the seed-rich cone is ripped apart by hungry seed carriers (who’ve included, over the years, not just birds and insects, but also dinosaurs, pterosaurs, and bats—these trees have been eaten by just about everybody).

But what if you can’t find a mate? The tree in London is a male. It can make pollen. But it can’t make the seeds. That requires a female.

Researchers have wandered the Ngoye Forest and other woods in Africa, looking for an E. woodii that could pair with the one in London. They haven’t found a single other specimen. They’re still searching. Unless a female exists somewhere, E. woodii will never mate with one of its own.

But it survives. Plant geneticists have cloned it.

Photograph Courtesy of Mark W. Skinner, hosted by the USDA-NRCS PLANTS Database
Photograph Courtesy of Mark W. Skinner, hosted by the USDA-NRCS PLANTS Database

Indeed, botanic gardens across the world asked Kew for clones, or “offsets,” and now you can see genetically identical versions on display in Europe, Australia, California, South Africa. The plant is frozen genetically. It’s a living fossil, “an example of the curious but expanding process of the democratization of rarity,” says science writer Richard Mabey. It might be terminal, but if you like you can shoot a selfie in front of its exact genetic doppleganger. Or visit the original. Or maybe even buy a clone for yourself.

Cycads (there are several surviving species) are popular garden plants. Some of the rarest are bought and sold secretly. “Enormous sums of money change hands,” says the Kew Gardens website, “and because of the rarity of the species and their colourful history, offsets can sell for as much as $20,000 each.”

Left: Photograph by Julian Parker, Getty; Right: Photograph by Todd Williamson Archive, Getty
Left: Photograph by Julian Parker, Getty; Right: Photograph by Todd Williamson Archive, Getty

The problem is serious, Kew says:

It is so serious that the San Diego Police Department in southern California assigned an officer to ‘cycad beat’ to monitor these precious plants. Elsewhere in the Hollywood Hills, Brad Pitt, Oprah Winfrey, [the late] David Bowie and Kevin Costner are among the celebrities that cycad-sellers report as collectors. ”I planted a huge grove of them in Brad Pitt’s garden,” says Jay Griffith, his landscape designer. ”And Brad flipped. He kept saying, ‘I want more and more.’ To me, they are most majestic when you plant gobs of them. You expect a triceratops to come around the corner and just gobble them up.” Brad is not infringing any regulations though: his cycads are the commoner cycad species, Cycas revoluta, the so-called sago palm.

Genetically Engineered Females

There is even a move, supported by Kew, to solve E. woodii’s problem scientifically. Plant geneticists have taken pollen from our still fertile surviving male and fertilized a very close cycad cousin, E. natalensis. The hope is, by “back-crossing” the two plants, they may eventually create a very close genetic approximation of a female E. woodii and so reboot the species.

This reminds Richard Mabey of “the scientific dream that woolly mammoth hybrids may be brought back from the dark world of the extinct by inserting fragments of fossil DNA into elephant genes.”

We’re trying it with animals. Why not with plants?

Yes, why not?

To Stay or Go?

Interesting question. On the one hand, we humans have crowded the world, hemmed in, poisoned and savaged any number of plants, denying them the space to grow and thrive, so shouldn’t we, when the occasion arises, repair what we’ve done? Restore when we can?

These cycads come down to us through a long tunnel of time; they’re like a chain letter from a “magical once” (as Oliver Sacks wrote). Somehow they’ve made it down to us, and isn’t our duty to keep them going, to not break the chain?

Maybe. But on the other hand, if the only way to keep them going is to take them to a lab, add a gene here, subtract one there, and try to engineer back what once was—what have we done? Is this still a “natural’ cycad? An almost-but-not-quite female cycad would keep the line going, but whose line is it then? Its own? Ours? Whose?

There’s something not quite right with scuffling through the scrapheap of disappearing plants and animals, choosing a favorite few, and “pickling” them, as Richard Mabey says, to preserve their ancientness, when we know full well that a truly living thing must make its way on its own, must adapt, mutate, crossbreed, or die. An “almost” version of a cycad may look right, but we know deep down that the chain has been broken. This is not a real descendant. It’s our clever substitute.

So I don’t want to rescue the loneliest plant in the world. I want it to get lucky.

Drawing by Robert Krulwich
Drawing by Robert Krulwich

Which could still happen. After all, there are acres and acres of uninspected bush in South Africa. Somewhere, on the side of a hill, tucked up against a rock, hanging in a shadow, I can still imagine a shy female E. woodii. She could be out there, waiting.

I’ve written about E.woodii before, so this is, in effect, a rethink, occasioned by my reading Richard Mabey’s wonderful new book of plant essays, The Cabaret of Plants (W. W. Norton & Company, 2016). The last time I wrote about the lonely cycad in London, I was all for saving it and unapologetically mournful. Now, thanks to Mabey, I’m finding this tale richer and harder to resolve. Which is a good thing. The great British biologist Richard Fortey talks about the London E.woodii in his classic Life: An Unauthorized Biography (Vintage, 1997). Oliver Sacks describes his personal encounter with the Kew cycad in The Island of the Colorblind (Vintage, 1997).


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Can a Plant Remember? This One Seems to—Here’s the Evidence

There’s this plant I’ve heard about that had a really bad afternoon a few years ago. It was in its pot bothering nobody and then, suddenly, it fell. Not once, but 56 times. (I’ll explain in a minute.) But it’s a plant. Things happen to plants, and as far as I know, they go on as before. They don’t have brains. They have no way to “remember” anything. They’re not animals. So I figure even 56 consecutive falls left no lasting impression.

I figured wrong. I just read an eye-popping paper by Monica Gagliano, associate professor of biology at the University of Western Australia. She’s got a plant that not only “remembered” what happened to it but stored that memory for almost a month. She saw this happen! Here’s the plant:

Picture of mimosa pudica leaves folding in after they are touched
Sensitive plant, shame plant (Mimosa pudica), flower and leaf, leaves sensitiv, leaflets folded after touching
Photograph by blickwinkel, Alamy

Gardeners call Mimosa pudica “the sensitive plant,” because if you touch it even lightly or drop it or disturb it, within seconds it folds its teeny leaves into what looks like a frightened or defensive curl. It’s fun to watch it get all shy (two and a half million people have seen this pokey, pokey video. You don’t have to watch it all, but it’ll get you in the mood.)

OK, so it’s highly sensitive. Knowing this, here’s what Gagliano did: She got a bunch of Mimosa pudicas, put them in pots, then loaded each one onto a special plant-dropping device using a sliding steel rail that worked like this:

Drawing by Robert Krulwich
Drawing by Robert Krulwich

Each potted plant was dropped roughly six inches, not once, but 60 times in a row at five-second intervals. The plants would glide into a soft, cushiony foam that prevented bouncing. The drop was sufficiently speedy to alarm the plant and cause its teeny leaves to fold into a defensive curl.

To “Eeek!” or Not to “Eeek!”

Six inches, however, is too short a distance to do harm, so what Gagliano wondered was: If she dropped 56 plants 60 times each, would these plants eventually realize nothing terrible was going to happen? Would any of them stop curling?

Or, to put it another way: Could a plant use memory to change its behavior?

To find out, she kept going with her experiment. And, as she writes in her paper, fairly quickly “observed that some individuals did not close their leaves fully when dropped.” In other words, plants seemed to figure out that falling this way wasn’t going to hurt, so more and more of them stopped protecting themselves—until, as she later told a room full of scientists, “By the end, they were completely open … They couldn’t care less anymore.”

Drawing by Robert Krulwich
Drawing by Robert Krulwich

Is this evidence of remembering, or is it something else? Maybe, skeptics suggested, all we’re seeing is a bunch of exhausted plants. Curling is work. It takes energy. After 60 drops, these plants may simply be pooped out—that’s why they don’t trigger their defenses. But Gagliano, anticipating this question, took some of those “tired” plants, put them in a shaker, shook them, and instantly they curled up again. “Oh, this is something new,” she imagined them saying, something that hasn’t happened before. That sense of a “before,” she said, is the best explanation for the plants’ change in behavior. They didn’t curl up again because “before” they’d learned there was no need. And they remembered.

A week later—after the shakings—she resumed her drops, and still the plants failed to get alarmed. Their leaves stayed open. She did it again, week after week, and after 28 days, these plants still “remembered” what they’d learned. That’s a long time to store a memory. Bees, she noted, forget what they’ve discovered in a couple of days.

But Without a Brain, How Do They Do It?

“Plants may lack brains,” Gagliano says in her paper, “but they do possess a sophisticated … signaling network.” Could there be some chemical or hormonal “unifying mechanism” that supports memory in plants? It wouldn’t be like an animal brain. It would be radically different, a distributed intelligence, organized in some way we don’t yet understand. But Gagliano thinks Mimosa pudica is challenging us to find out.

Michael Pollan, writing in the New Yorker, hung out with Gagliano last year, went with her to a science meeting, and vividly describes how she was roundly dismissed by many biologists, who bridle at the idea that any plant could be “intelligent.” Plants, they insist, are mainly genetic robots—they can’t learn from experience or change behavior. To say they can “generates strong feelings,” Pollan writes, “perhaps because it smudges the sharp line separating the animal kingdom from the plant kingdom.”

Drawing by Robert Krulwich
Drawing by Robert Krulwich

Plants have always been the bronze medalists, one step down from the animals, two steps down from us, the golden ones. By giving plants animal-like talents, Gagliano is mucking up the hierarchies, challenging the order of things.

We like to think because we have such big brains, we’re exceptional. Our trillions of neurons are keys to memory, feelings, consciousness. Brainless creatures by definition can’t do what we do—so of course, plants can’t “remember.”

But Gagliano says maybe they can.

“What we have shown here,” she says at the end of her paper “leads to one clear, albeit quite different, conclusion: the process of remembering may not require the conventional neural networks and pathways of animals; brains and neurons are just one possible, undeniably sophisticated, solution, but they may not be a necessary requirement for learning.”

And who knows? Maybe she just found the plant that will one day prove her right.

Editor’s Note: This post was originally published with a photo of a plant that was misidentified as Mimosa Pudica. We have since updated the post with a new image.

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People Sometimes Like Stinky Things—Here’s Why

Updated September 30, 2015

A corpse flower smells like a heady mix of rotten fish, sewage, and dead bodies. It’s a stench meant to draw flies, but just as surely, it draws tourists. Braving a blustery Chicago night, thousands of people lined up Tuesday for a whiff of a corpse flower named Alice at the Chicago Botanic Garden.

This woman shows a classic "disgusted" face in a video about the 2013 blooming of a corpse flower (see video, top).
This woman shows a classic “disgusted” face in a video about the 2013 blooming of a corpse flower (see video, top).

In fact, the demand to see and smell a corpse flower is so great that botanical gardens now vie to own one. Gardeners lavish them with care, hoping to force more stinky blooms from a plant whose scent is so rare (up to a decade between flowerings) and so fleeting (eight to 12 hours) that visitors are often disappointed to miss peak stench.

But why do people want to smell the thing? The reaction is usually the same: the anticipation, the tentative sniff, then the classic scrunched-up face of disgust. And yet everyone seems happy to be there.

It turns out there’s a name for this: benign masochism.

Psychologist Paul Rozin described the effect in 2013 in a paper titled “Glad to be sad, and other examples of benign masochism.” His team found 29 examples of activities that some people enjoyed even though, by all logic, they shouldn’t. Many were common pleasures: the fear of a scary movie, the burn of chili pepper, the pain of a firm massage. And some were disgusting, like popping pimples or looking at a gross medical exhibit.

The key is for the experience to be a “safe threat.”

“A roller coaster is the best example,” Rozin told me. “You are in fact fine and you know it, but your body doesn’t, and that’s the pleasure.” Smelling a corpse flower is exactly the same kind of thrill, he says.

It’s a bit like kids playing war games, says disgust researcher Valerie Curtis of the London School of Hygiene and Tropical Medicine. “The ‘play’ motive leads humans (and most mammals, especially young ones) to try out experiences in relative safety, so as to be better equipped to deal with them when they meet them for real,” she says.

People around the world make the same face when disgusted, with a downturned mouth and sometimes a protruding tongue.
People around the world make the same face when disgusted, with a downturned mouth and sometimes a protruding tongue.

So by smelling a corpse flower, she says, we’re taking our emotions for a test ride. “We are motivated to find out what a corpse smells like and see how we’d react if we met one.”

Our sense of disgust, after all, serves a purpose. According Curtis’ theory of disgust, outlined in her insightful book “Don’t Look, Don’t Touch, Don’t Eat,” the things most universally found disgusting are those that can make us sick. You know, things like a rotting corpse.

Yet our sense of disgust can be particular. People, it seems, are basically fine with the smell of their own farts (but not someone else’s). Disgust tends to protect us from the threat of others, while we feel fine about our own grossness.

Then there are variations in how we perceive odors. Some smells are good only in small doses, as perfumers know. Musk, for instance, is the base note of many perfumes but is considered foul in high concentrations. Likewise for indole, a molecule that adds lovely floral notes to perfumes but is described as “somewhat fecal and repulsive to people at higher concentrations.”

University of California Botanical Garden
University of California Botanical Garden

No one has yet, to my knowledge, tried out a low dose of corpse flower in a perfume (though you can try on an indole brew in “Charogne,” which translates to “Carrion,” by Etat Libre d’Orange). But someone could. There’s an entire field of perfumery—called headspace technology, it was pioneered by fragrance chemist Roman Kaiser in the 1970s—that’s dedicated to capturing a flower’s fragrance in a glass vial and then re-creating the molecular mix chemically. I would love to see someone give eau de corpse flower a whirl, if only they can find a headspace vial large enough.

The stench of a corpse flower, after all, is a mix of compounds, including indole and sweet-smelling benzyl alcohol in addition to nasties like trimethylamine, found in rotting fish. So I’d be very curious to know if a small amount of corpse flower would be a smell we would hate, or maybe love to hate.

I’ll leave you with my favorite example of a “love to hate” smell, from my childhood in the 1980s. At a time when I loved Strawberry Shortcake dolls and scratch-and-sniff stickers, the boys in my class were playing with He-Man dolls. Excuse me, action figures. And among the coolest, and grossest, of them was Stinkor. He was black and white like a skunk, and his sole superpower was to reek so badly that his enemies would flee, gagging.

To give Stinkor his signature stink, Mattel added patchouli oil to the plastic he was molded from. (This confirms the feelings of patchouli-haters everywhere.) It meant that you couldn’t wash Stinkor’s smell away, and it wouldn’t fade like my Strawberry Shortcakes did. The smell was one with Stinkor. And of course, children loved him.

Writer Liz Upton describes the Stinkor figure that she and her brother adored (their mother did not). The kids would pull Stinkor out and scratch at his chest, smelling him again and again. “Something odd was going on here,” Upton writes. “Stinkor smelled dreadful, but his musky tang was strangely addictive.”

If you’re the kind of benign masochist who wants to smell Stinkor for yourself, you can pay $125 or more for a re-released collector’s edition Stinkor—or you can just find an old one on eBay. The amazing thing: 30 years later, the original Stinkor dolls still stink. And people still buy them.

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Seeds That Defied Romans, Pirates, and Nazis

Our story starts quietly in a museum. In a cabinet. There, in the dark, sits a small batch of seeds: Persian silk tree seeds. They come from China. They were taken, probably secretly, from Beijing to London by a British diplomat in 1793. The British wanted to grow silk.

Flash forward to 1940. German bombers are flying over London. An incendiary bomb hits the botany section of London’s British Museum, smashing our cabinet, releasing the seeds. They fly off, land in the rubble, and get doused by London’s fire brigade. Weeks later, museum workers see some sprouts growing at the bomb site—baby silk trees. They’d germinated after 150 years in a cabinet.

Drawing of a silk seedling emerging from a pile of rubble

Seeds can do that.

A seed, after all, is an embryo, a potential plant waiting for its moment to grow. It has what it needs to begin. But it can also put itself on pause. It can wait. The question is, For how long? No seed can last forever. But for how long can it pause?

Another Story

Drawing of Jan Teerlink, a 19th century spice merchant, and a Pirate

Jan Teerlink, a spice merchant, is heading home to Europe aboard a Prussian ship, the Henriette. It’s 1803. He’s bringing tea and silk to Amsterdam from the Far East. In his luggage is a red, leather-bound notebook, and stashed between its pages are 40 small paper packets of seeds, including those of a pleasing flowering plant called the pincushion protea. Teerlink collects seeds. While sailing on the Atlantic, his ship is attacked by British buccaneers (pirates with an official license to steal whatever they can from unfriendly nations). They overpower the crew, seize Teerlink’s cargo, and confiscate his notebook. Being legal pirates, they then deposit the notebook, packeted seeds still inside, with the British Admiralty in London. No one notices the seeds. The book is sent to a storage facility in the Tower of London. There it sits. Later, it’s transferred to the U.K.’s National Archives. It was here that the book was found a few years ago by a visiting Dutch professor, the seeds still in their packets. The professor planted them, and, after 200 years, produced three lovely, healthy plants, including a pincushion. That’s after a two-century pause. Can we do better?

OK, Another Story

Drawing of an ancient rattle made of a walnut

We can. In the 1960s archaeologists found a tomb in Argentina that contained an ancient rattle. It was made of a walnut shell (Juglans australis) with canna lily seeds banging around inside. They opened the nut, removed the seeds, planted some, and got a lily. When they carbon dated the seed, it was 600 years old. A six-century pause! Is that the record?

No! An Even Better Story

When Flavius Silva, a Roman general, broke through Jewish defenses at Masada in the winter of A.D. 72-73, his legions rushed into a complex of palaces built by Herod the Great, looking to hunt down a band of Jewish rebels who had gathered on the plateau, swearing eternal resistance to Rome. He found … not a one. There had been almost a thousand Jews at the outpost—men, women, and children—but when the Romans got to them, they were all dead. They’d committed mass suicide. Just before they died, they lugged all their provisions, money, valuables, and food to a warehouse and burned the place down. It was a smokey hump. The Romans left. The hump stayed.

Color lithograph of the romans building a ramp during their siege on Masada
©Look and Learn, color lithograph by Jose Luis Salinas
Masada: Fortress That Knew Not Surrender. The Romans spent months building a ramp and a siege tower.

Two thousand years later, a team of archaeologists began digging carefully through that refuse pile. They found coins, tools, salt, grains, and, as you probably guessed, seeds. Back in Jesus’ time (and Cleopatra’s and King David’s) Judea was famous for its sweet, flavorful dates. They were exported across the Roman Empire and celebrated in the Bible and the Koran. And in that dry, protected ruin, archaeologists found a little jar with a batch of date seeds inside. The seeds were sent to Bar-Ilan University, where they were carbon dated and found to be a little older than the siege of Masada; they’d been collected 2,000 years ago.

Picture of a two thousand year old palm seed called Methuselah, in a clay-colored pot
A photograph of the date palm called Methuselah taken in 2008 shows the plant, which sprouted from a 2,000-year-old seed, when it was about three years old. It’s now about ten years old and ten feet (three meters) tall. Photograph by Arava Institute, EPA
A photograph of the date palm called Methuselah taken in 2008 shows the plant, which sprouted from a 2,000-year-old seed, when it was about three years old. It's now about ten years old and ten feet (three meters) tall.

Would they germinate? No way, it was thought. In his new book The Triumph of Seeds, Thor Hanson interviews Elaine Solowey, an agricultural expert at Kibbutz Ketura in the Negev desert, who said, “I really didn’t expect anything to come up.” She had been given three of the recovered seeds, bathed in a hormone-rich solution. But still, she told Thor, “I thought those seeds were as dead as doornails. Deader than doornails.” But, what the heck, she planted them.

And—against all expectations—she got a sprout. That sprout grew a foot, then five feet, then ten feet. When National Geographic last checked, in March this year, Solowey’s palm tree had blossomed and produced healthy dollops of pollen. So it’s a male palm. To produce a true Judean date, it will need a female palm companion, and Solowey says that while she hasn’t yet found an exact ancient species match, she’s mated her ancient palm with a modern one and gotten a fruit. So her 2,000-year-old baby tree can now, as she proudly and coyly put it, “make dates.”

It also has its own bachelor pad. “We built him his own gated garden, with his own watering system, burglar alarm, and security camera,” Solowey told Hanson.

Picture of a date palm referred to as ''Methuselah'' in a fenced in area
”Methuselah” the Date Palm, sprouted from a 2,000 year old seed that was found in the excavations of Masada. Here it is, photographed in 2014. Photograph Courtesy of www.HolyLandPhotos.org
''Methuselah'' the Date Palm, sprouted from a 2,000 year old seed that was found in the excavations of Masada, March 2014

As far as we know, that Masada date seed holds the record for Longest Known Pause Before Growing.

What seeds do when they’re doing nothing is a matter of some debate. When you get dried grass seeds at a gardening center, they are alive. They don’t look it or feel it, but when you scatter them on the wet, moist ground, they perk into action. If they were dead, they’d stay dead. They’re either dormant—which seems to mean they’re in a deep pause—or they’re metabolizing (very, very slowly), or they’re in a mysterious category we sometimes call suspended animation, which is close to dead but not. Whatever their secret, they have, some of them, enormous staying power, which leads me to my very last (I promise) story.

Once Upon a Time There Was a Squirrel

Drawing of a squirrel eating a seed in a pile of rubble

Thirty-two thousand years ago—yes, we’re making a huge leap here—a squirrel living along the Kolyma River in what is now Russian Siberia was collecting seeds, as squirrels do, and storing them in an underground burrow, when all of a sudden an avalanche, mudslide, terrible storm, or something landed and smothered the squirrel, the burrow, the seeds, everything. There must have been a bunch of squirrels in the area because, according to the New York Times, when archaeologists began digging a few years ago, they found “more than 600,000 seeds and fruits” at the site. They tried to make the seeds grow. They wouldn’t. But a little bit of tissue from a bit of surviving fruit was cloned and turned into a living, working plant, the narrow-leafed campion (Silene stenophylla).

Picture of the narrow leaf campion growing in beakers
Outgrowths of the Silene stenophylla, considered as the oldest plant ever to be regenerated, are seen inside containers at a laboratory of the Institute of Cell Biophysics under the Russian Academy Of Sciences in the town of Pushchino. Photograph by Denis Sinyakov, Reuters
Outgrowths of the Silene stenophylla, considered as the oldest plant ever to be regenerated, are seen inside containers at a laboratory of the Institute of Cell Biophysics under the Russian Academy Of Sciences in the town of Pushchino, some 100 km (62 miles) south of the capital Moscow, February 24, 2012. The seeds of an extant species of a flowering plant, also known as the narrow-leafed campion, were found by Russian scientists on the banks of the Kolyma River in Siberia in an Ice Age ground-squirrel's burrow containing fruit and seeds that had been stuck in the permafrost for about 30,000 years. The permafrost, which serves as a natural depository for ancient life forms, may help researchers and scientists with their future experiments to revive other species, according to local media.

If a bit of tissue can make a 32,000-year leap, then there’s got to be a seed somewhere, maybe lots and lots of seeds, that can hold on for longer than 2,000 measly years. I suspect we’ve got champions quietly resting all over the globe, not telling us that they’re still there—all of them waiting for the drop of water, the touch of flame, the burst of warmth that kicks them back to life.

This story isn’t over.

If you want a truly comprehensive listing of the longest lasting seeds, check out this botany textbook, but if you’re just curious and want a rip-roaring read, then Thor Hanson’s The Triumph of Seeds is the newest and best one around. For a gander at the spectacular things seeds can do, check out my earlier columns “Strange Things Happen to Guys Who Wear Pants” and “How Do Plants Know Which Way Is Up and Which Way Is Down?”

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With Sonar-Reflecting Leaves, Plant Lures Bats to Poo in it

Imagine a bat flying through the jungle of Borneo. It calls out to find a place to spend the night. And a plant calls back.

The plant in question is Nepenthes hemsleyana—a flesh-eating plant that’s terrible at eating flesh. It’s a pitcher plant and like all its kin, its leaves are shaped like upright vases. They’re meant to be traps. Insects should investigate them, tumble off the slippery rim, and drown in the pool of liquid within the pitcher. The pitcher then releases digestive enzymes to break down the corpses and absorb their nitrogen—a resource that’s in short supply in the swampy soils where these plants grow.

But N.hemsleyana has very big pitchers that are oddly short of fluid and that don’t release any obvious insect attractants. And when Ulmar Grafe from the University of Brunei Darussalam looked inside them, he saw seven times fewer insects than in other pitchers.

Instead, he found small bats.

Grafe enlisted the help of Caroline and Michael Schöner from the University of Greifswald, a wife-and-husband team who had worked on bats. Together, they repeatedly found the same species—Hardwicke’s woolly bat—roosting inside the plants, and nowhere else. In some cases, youngsters snuggled next to their parents.

The plant had adapted to accommodate these tenants: that’s why their pitchers are roomier than average, and have little fluid. And the bats repay them with faeces. Bat poo—guano—is rich in nitrogen, and the team found that this provides the pitcher with a third of its supply. The carnivorous plant has largely abandoned its insect-killing ways and now makes a living as a bat landlord.

This was all published in 2011. Since then, the Schöners and Grafe have discovered another extraordinary side to the relationship between the bat and the pitcher. “It started when we were searching for the plants in the forest,” says Michael Schöner. “We had a lot of difficulty. The vegetation is dense and the pitchers are green.”

This problem should be even worse for the woolly bats. They navigate by echolocation: they make high-pitched squeaks and visualise the world in the reflecting echoes. “Inside these forests, you get a reflection from everything, every single plant and leaf that’s there,” says Schöner. To make matters worse, the bats must distinguish N.hemsleyana from a closely related, similarly shaped, and far more common species, that’s unsuitable for roosting. How do they do it?

In South America, there are flowers with a similar problem: they are pollinated by bats, and must somehow attract these animals amid the clutter of the rainforest. They do it by turning their flowers into sonar dishes, which specifically reflect the calls of echolocating bats. The Schöners wondered if their pitcher plant had also evolved acoustic cat’s eyes.

They contacted Ralph Simon from the University of Erlangen-Nürnberg, who showed up with a robotic bat head.

It has a central loudspeaker and two microphones that look like a bat’s ears. He used it to “ensonify” the pitchers with ultrasonic calls from various directions, and measure the strength of the echoes.

The team found that the back wall of N.hemsleyana—the bit that connects its lid to its main chamber—is unusually wide, elongated, and curved. It’s like a parabolic dish. It strongly reflects incoming ultrasound in the direction it came from, and over a large area. Other pitcher plants that live in the same habitat don’t have this structure. Instead, their back walls reflect incoming calls off to the sides. So, as the woolly bats pepper the forest with high-pitched squeaks, the echoes from N.hemsleyana should stand out like a beacon.

Is this what actually happens? To find out, the team modified the pitchers’ reflectors. They enlarged them by building up the sides with tape, reduced them by trimming the sides with scissors, and cut them off entirely (while propping the lids up with toothpicks). Then, they hid the modified plants among some shrubbery, and placed them in a tent with some bats.

The bats took much less time to approach the pitchers with enlarged or unmodified reflectors than those with trimmed or amputated ones. And when given a choice, they mostly entered pitchers with natural, unaltered reflectors. They seem to be attracted to strong echoes but when they get close, they make a more considered decision about whether they have found the right species.

The team also found that the woolly bats produce the highest-pitched calls ever recorded from a bat. They don’t need such high frequencies to hunt their prey and, indeed, other insect-eating bats are nowhere near that high-pitched. Instead, the team believes that the calls are particularly well suited to detecting targets in cluttered environments. Between these squeaks and the plant’s reflectors, both partners can find each other in the unlikeliest of circumstances. The bat gets a home, and the plant gets its faecal reward.

Reference: Schöner, Schöner, Simon, Grafe, Puechmaille, Ji & Kerth. 2015. Bats Are Acoustically Attracted to Mutualistic Carnivorous Plants. Current Biology http://dx.doi.org/10.1016/j.cub.2015.05.054

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The Little Boy Who Should’ve Vanished, but Didn’t

He was 12 years old. He was a slave. He’d had no schooling. He was too young, too unlettered, too un-European; he couldn’t have done this on his own. That’s what people said.

Picture of a drawing of an older man and a young boy facing  a vanilla plant with their backs to the viewer
Drawing by Robert Krulwich
Drawing by Robert Krulwich

Edmond (he had no last name—slaves weren’t allowed them) had just solved a botanical mystery that had stumped the greatest botanists of his day. In the early 1800s he was a child on a remote island in the Indian Ocean, and yet, against overwhelming odds, Edmond would get credit for his discovery—and for the most surprising reasons. I want to tell you his story. So I’ll start here, with a plant.

Picture of a drawing of a vanilla plant
Drawing by Robert Krulwich
Drawing by Robert Krulwich

This is a vanilla plant (or my version of one). It’s a vine. It climbs, sometimes way high, and when it flowers and is visited by a pollinator, it produces a bunch of long, stringy beans. Properly treated, those beans give off the flavor we associate with vanilla.

Picture of a drawing of Anne of Austria holding a mug of hot chocolate
Drawing by Robert Krulwich
Drawing by Robert Krulwich

When Spanish explorers brought vanilla from Mexico, it was mixed with chocolate and became a classy sensation, fancied by kings, queens, and, pretty soon, everybody else. In his book Vanilla: Travels in Search of the Vanilla Orchid, journalist Tim Ecott reports that Anne of Austria, daughter of Philip III of Spain, drank it in hot chocolate. Madame de Pompadour, one of the great hostesses (and mistresses) of King Louis XV, flavored her soups with it.

Picture of Madame de Pompadour with a bowl of steaming soup in front of her
Drawing by Robert Krulwich
Drawing by Robert Krulwich

Francisco Hernandez, physician to King Philip II of Spain, called it a miracle drug that could soothe the stomach, cure the bite of a venomous snake, reduce flatulence, and cause “the urine to flow admirably.”

Picture of a drawing of a man peeing
Drawing by Robert Krulwich
Drawing by Robert Krulwich

And, best of all, it was a sexual picker upper. Bezaar Zimmerman, a German physician, claimed in his treatise “On Experiences” (1762) that, “No fewer than 342 impotent men, by drinking vanilla decoctions, have changed into astonishing lovers of at least as many women.”

Picture of a drawing of a woman laying her head on the shoulder of a man standing next to a vanilla bottle
Drawing by Robert Krulwich
Drawing by Robert Krulwich

Demand, naturally, shot sky high. By the late 18th century, a ton of Mexican vanilla was worth, writes Ecott, “its weight in silver.”

With profit margins growing, a few plants were hustled out of Mexico to botanical gardens in Paris and London, then on to the East Indies to see if the plant would grow in Europe or Asia.

It grew, but it wouldn’t fruit, wouldn’t produce beans. Flowers would appear, bloom for a day, fold up, and fall off. With no beans, there could be no vanilla extract, and therefore nothing to sell. The plant needed a pollinator. In Mexico a little bee did the deed. Nobody knew how the bee did it.

Picture of a drawing of a bee saying 'Shhhhh'
Drawing by Robert Krulwich
Drawing by Robert Krulwich

What to do? In the 1790s people knew about plant sex. Bees, they knew, were pollinators.

If people could only figure out where vanilla’s sexual parts were hiding, they could become bee substitutes.

Enter the 12-Year-Old

They kept trying. One plantation owner, Ferréol Bellier-Beaumont, on the island of Réunion halfway between India and Africa, had received a bunch of vanilla plants from the government in Paris. He’d planted them, and one, only one, held on for 22 years. It never fruited.

The story goes that one morning in 1841, Bellier-Beaumont was walking with his young African slave Edmond when they came up to a surviving vine. Edmond pointed to a part of the plant, and there, in plain view, were two packs of vanilla beans hanging from the vine. Two! That was startling. But then Edmond dropped a little bomb: This wasn’t an accident. He’d produced those fruits himself, he said, by hand-pollination.

No Way

Bellier-Beaumont didn’t believe him—not at first. It’s true that months earlier the older man had shown Edmond how to hand-pollinate a watermelon plant “by marrying the male and female parts together,” but he’d had no success with vanilla. No one had.

But after his watermelon lesson, Edmond said he’d sat with the solitary vanilla vine and looked and probed and found the part of the flower that produced pollen. He’d also found the stigma, the part that needed to be dusted. And, most important, he’d discovered that the two parts were separated by a little lid, and he’d lifted the flap and held it open with a little tool so he could rub the pollen in. You can see what Edmond did in this video:

Edmond had discovered the rostellum, the lid that many orchid plants (vanilla included) have, probably to keep the plant from fertilizing itself. Could you do it again, Bellier-Beaumont asked? And Edmond did.

This was news. Big news. Bellier-Beaumont wrote his fellow plantation owners to say Edmond had solved the mystery, then sent him from plantation to plantation to teach other slaves how to fertilize the vanilla vine.

And so the Indian Ocean vanilla industry was born.

In I841, Réunion exported no vanilla. By 1848, it was exporting 50 kilograms (.0055 tons) to France; by 1858, two tons; by 1867, 20 tons; and by 1898, 200 tons. “By then,” Tim Ecott writes, “Réunion had outstripped Mexico to become the world’s largest producer of vanilla beans.”

Picture of a drawing of a graph showing vanilla exports from Reunion
Drawing by Robert Krulwich
Drawing by Robert Krulwich

The planters were getting rich. What, I wondered, happened to Edmond?

Well, he was rewarded. His owner gave him his freedom. He got a last name, Albius. Plus, his former owner wrote the governor, saying he should get a cash stipend “for his role in making the vanilla industry.”

The governor didn’t answer.

Edmond left his master and moved to town, and that’s when things went sour.

He fell in with a rough crowd, somehow got involved in a jewelry heist, and was arrested, convicted, and sentenced to five years in jail. His former owner again wrote the governor.

“I appeal to your compassion in the case of a young black boy condemned to hard labor … If anyone has a right to clemency and to recognition for his achievements, then it is Edmond … It is entirely due to him that this country owes [sic] a new branch of industry—for it is he who first discovered how to manually fertilize the vanilla plant.”

Picture of a drawing that says Entirely Due to Him
Drawing by Robert Krulwich
Drawing by Robert Krulwich

The appeal worked. Edmond was released. But what catches my eye here is Bellier-Beaumont’s choice of “entirely.” Our new vanilla business, he says, is “entirely” due to Edmond. He’s giving the former slave full credit for his discovery and retaining none for himself. That’s rare.

Then, all of a sudden, Edmond had a rival. A famous botanist from Paris—a scholar, a high official knighted for his achievements—announced in the 1860s that he, and not the slave boy, had discovered how to fertilize vanilla.

Picture of a drawing of a man with a beard holding a vanilla plant and looking suspicious
Drawing by Robert Krulwich
Drawing by Robert Krulwich

Jean Michel Claude Richard claimed to have hand-pollinated vanilla in Paris and then gone to Réunion in 1838 to show a small group of horticulturists how to do it. Little Edmond, he presumed, had been in the room, peeked, and then stolen the technique.

So here’s a prestigious scholar from the imperial capital asserting a claim against a 12-year-old slave from a remote foreign island. What chance did Edmond have?

Picture of a drawing of a young boy who was a slave facing off with an old scholarly French man
Drawing by Robert Krulwich
Drawing by Robert Krulwich

He was uneducated, without power, without a voice—but luckily, he had a friend. Once again, Edmond’s former master, Bellier-Beaumont, jumped into action, writing a letter to Réunion’s official historian declaring Edmond the true inventor. The great man from Paris, he said, was just, well, mis-remembering.

He went on to say that no one recalled Richard showing them how to fertilize orchids, but everybody remembers, four years later, Edmond teaching his technique to slaves around the island. Why would farmers invite Edmond to teach “if the process were already known?”

“I have been [Richard’s] friend for many years, and regret anything which causes him pain,” Bellier-Beaumont wrote, “but I also have my obligations to Edmond. Through old age, faulty memory, or some other cause, M. Richard now imagines that he himself discovered the secret of how to pollinate vanilla, and imagines that he taught the technique to the person who discovered it! Let us leave him to his fantasies.”

The letter was published. It’s now in the island’s official history. It survives.

Picture of an etching of Edmond Albius with the vanilla plant in his hands
Etching of more adult Edmond Albius
Etching of more adult Edmond Albius

And Yet, a Miserable End

Edmond himself never prospered from his discovery. He married, moved back to the country near Bellier-Beaumont’s plantation, and died in 1880 at age 51. A little notice appeared in the Moniteur, the local paper, a few weeks after he died. Dated Thursday, 26 August, 1880, it read: “The very man who at great profit to his colony, discovered how to pollinate vanilla flowers has died in the hospital at Sainte-Suzanne. It was a destitute and miserable end.” His long-standing request for an allowance, the obituary said, “never brought a response.”

Picture of the Edmond Albius Statue in
The statue of Edmond in Réunion
Photograph courtesy of Yvon/Flickr

But a hundred years later, the mayor of a town on Réunion decided to make amends. In 1980 or so, a statue was built to honor Edmond. Writer Tim Ecott decided to take a look. He bought a bus ticket on the island’s “Vanilla Line,” rode to the stop marked “Albius,” got off, and there, standing by himself is Edmond (in bronze or concrete? I can’t tell). He’s dressed, Ecott says, like a waiter, with a narrow bow tie and jacket. He’s not wearing shoes: Slaves weren’t allowed shoes or hats. But he’s got a street named after him, a school named after him. He has an entry on Wikipedia. He’s survived.

Picutre of a drawing of a man with a beard holding a vanilla plant and looking sad
Drawing by Robert Krulwich
Drawing by Robert Krulwich

And the guy who tried to erase him from history, Richard? I looked him up. He also has a Wikipedia entry. It describes his life as “marred by controversy,” mentions his claim against Edmond, and concludes that “by the end of the 20th century,” historians considered the 12-year-old boy “the true discoverer.” So despite his age, poverty, race, and status, Edmond won.

This is such a rare tale. It shouldn’t be. But it is.

Editor’s Note: This post has been updated to correctly reflect the title of Tim Ecott’s book.

Two books recount Edmond’s story. Tim Ecott’s Vanilla: Travels in Search of the Vanilla Orchid is the most thorough and original, but How to Fly a Horse: The Secret History of Creation, Invention and Discovery by Kevin Ashton tells the same tale and marvels that a slave on the far side of the world, poor and non-white, could get credit for what he’d done. There is also Ken Cameron’s Vanilla Orchids: Natural History and Cultivation, a book that contains Thomas Jefferson’s handwritten recipe for vanilla ice cream.

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Shrub Attracts Pollinators By Glittering Under the Full Moon

On the cliffs of the Mediterranean, there grows an untidy, scrambling shrub called Ephedra foeminea. It isn’t the prettiest of plants, but once a year, in the middle of July, it becomes far more appealing. On the night of the full moon, the shrub exudes small, sweet droplets from its red cones. Without any clouds or trees in the way, these drops catch the full intensity of the moonlight, reflecting them into the eyes of passers-by. The shrub sparkles, as if covered in diamonds.

“We find it ever so beautiful,” says Catarina Rydin, from the University of Stockholm.

She thinks that the precisely timed lightshow attracts night-flying pollinators like moths and flies. After all, E.foeminea has no other obvious way of enticing these insects. It doesn’t produce scent and it doesn’t have bright white flowers that might stand out in the darkness. Instead, it relies on the moon, cloaking itself in reflective ‘pollination drops’ that shine like beacons.

This discovery was borne of frustration. Ephedra is part of an old lineage of plants that had their heyday during the reign of the dinosaurs, almost went extinct, and then stubbornly clung to existence. Rydin wanted to know why. She and her student Kristina Bolinder started studying two European species to work out how they reproduce. Bolinder became so familiar with the wind-pollinated Ephedra distachya that she could predict its pollination schedule and plan trips to Greece accordingly. But E.foeminea proved to be much harder to predict. “We made mistakes basically every year,” says Rydin. They’d go, only to find no signs of pollination drops. They always had to wait.

In 2014, they made a trip in early July and “as usual, we came at the wrong time,” says Rydin. “No pollination drops, no pollinators. We could do nothing but wait.” Wait, and read. Rydin read up on insect pollinators. She read about how some insects can navigate by moonlight. And when she reviewed records and photos from their 2012 trip, the only one where they accidentally got the timing right, she noticed that there was a bright full moon in the sky. “We talked about it. We even said that we had bad luck with the moon this year,” she recalls. “But we still didn’t get it.”

A week passed and the duo became incredibly frustrated. They tried to take their minds off with a nice Greek dinner, “but all we could talk about was why the ******* plants did not go into pollination phase,” says Rydin. “And, I am not sure why, but all of a sudden we experienced a eureka moment! The moon in the photos from another year, the darkness at the field site this year, the articles about nocturnal insect navigation… Wait a minute now… What if…?”

The duo looked at old records, from their own trips and from the scientific literature as far back as 1910, and found that E.foeminea always releases pollination drops on the night of the full moon. “Not much data is available, but it all speaks the same language,” says Rydin. The full moon of July 2014 was due on the 12th, a few days away. So, they waited “to see if that was what the plants were waiting for. And so it was!” The moon appeared, and the shrubs started sparkling.

E.foeminea’s timing is unerringly precise. Even if its cones are mature earlier in the month, it waits till the full moon to produce its pollination drops. And if some cones are immature, the plant still forces them to exude droplets on that particular day. By contrast, the wind-pollinated E.distachya is unconnected to lunar cycles. It produces pollination drops at roughly the same time, regardless of what the moon is up to.

How does E.foeminea detect moonlight? “Short answer: we don’t know,” says Rydin. It might be able to detect small changes in light intensity. It’s also unclear why the full moon matters; surely the light of a half-moon would be sufficient to guide in pollinating insects? The difference, Rydin thinks, is that a full moon is not just brighter, but brighter for longer. “We think it is all about maximizing efficiency. Only at full moon do the insects have a moon to navigate by during the entire night.”

This strategy has clearly served E.foeminea well for a long time, but also makes it vulnerable to rain, clouds, and perhaps man-made lighting. Perhaps this is why E.foeminea grows much further away from local villages than E.distachya does. And perhaps this is why it seems to be the only Ephedra species to retain its ancient insect-pollinated strategy, while other members of the group have trusted their fates to wind instead.

More on moonlit liaisons: Clock gene and moonlight help corals to co-ordinate a mass annual orgy

Reference: Rydin & Bolinder. 2015. Moonlight pollination in the gymnosperm Ephedra (Gnetales). Biology Letters. http://dx.doi.org/10.1098/rsbl.2014.0993


Sciencespeak: Lazarus taxon

It’s a science fiction staple. An intrepid explorer is walking through the woods when they stumble across an ancient organism not seen for millions of years. Dinosaurs are choice for such appearances, but pterosaurs and other prehistoric critters do just as well. In text and on film, they manage to persist in some isolated pocket where extinction spared them. But such scenarios are not restricted to the realm of fantasy.

In July of 1943, while traveling through eastern China, forestry official Zhan Wang heard a tantalizing rumor. In the town of Moudao, the principal of Xian Agriculture High School told him, there grew a tree that no one could identify. That was enough for Zhan. He altered his travel route across Hubei Province to find the mystery tree, and, sure enough, he found it. With a few snips Zhan collected some branches and cones according to standard botanical protocol and was on his way.

Once he had a chance to fully examine his sample, though, Zhan wasn’t sure what the tree was. The plant’s anatomy resembled that of the Chinese swamp cypress – a tree known for decades – but small details of the leaves, branches, and cones were all wrong. Not wanting to go out on a limb, Zhan classified the tree as Glyptostrobus pensilis?, the question mark a reminder that the species might not be the swamp cypress, after all.

The next summer botanist Zhong-Lun Wu was looking through the herbarium collections at the National Central University at Chongqing when Zhan’s mystery cypress caught his eye. It looked like something new. This sparked a flurry of comparison and discussion among China’s botanists and dendrologists that ultimately arrived at a startling conclusion. The tree was not new to science. Astonishingly, it was a living species of Metasequoia – the “dawn redwood” that had been named from fossils just a few years before.

Some called Metasequoia a “living fossil“. Whether the term fits or not depends on what you think about how much the tree has changed in the last five million years or so. But there’s another term that definitely applies to discoveries like this. Metasequoia is a Lazarus taxon.

For those who are little shaky on their New Testament stories, Lazarus is the fellow that Jesus is said to have raised from the dead. And while the miracle of finding the Metasequoia was one of science, rather than religion, paleontologists Karl Flessa and David Jablonski coined the term Lazarus taxon for organisms that reappear after their presumed extinction.

The coelacanth is the most famous Lazarus taxon. Photo by Afernand74, CC BY-SA 3.0.
The coelacanth is the most famous Lazarus taxon. Photo by Afernand74, CC BY-SA 3.0.

There are plenty of other examples of Lazarus taxa. The most famous is the coelacanth – an ancient form of fish thought to have gone extinct over 66 million years ago only to turn up in a South African fish market. A genus of ant first found in amber, a midwife toad, and a whole group of marine invertebrates called monoplacophorans fit the bill, too, though the term isn’t restricted to living species.

“Lazarus taxon” was originally coined for organisms – from a single species up to an entire group – that seem to disappear during one of Earth’s “Big Five” mass extinctions only to pop up again in the fossil record. That’s because “fossilization lows” seem to immediately follow mass extinctions wherein, for one reason or another, not as many organisms wind up locked in stone. And applied more widely to the fossil record, the extensive list of Lazarus taxa includes a lineage of weasel-like protomammals called diademodontids that reappear in the Triassic rock of South Africa after an absence of 21 million years and a slew of odd invertebrates that were thought to have gone extinct by 501 million years ago before turning up in rocks 488-472 million years old.

So why do some creatures seem to blink out of the fossil record only to be revived? There’s more than one reason. The simplest is that the fossil record is not only incomplete, but incompletely-studied. There are fossil-bearing strata that have yet to feel the boots of curious paleontologists, and there are always significant specimens that get overlooked. Not to mention that recognizing living Lazarus taxa is an interdisciplinary effort that requires paleontologists and field biologists to be aware of what the other group is doing. There may be living species that count as Lazarus taxa but haven’t been recognized as such just yet.

Then there’s the nature of the fossil record itself. A species or lineage might go extinct in a given area but persist elsewhere. This geographic problem may be why we don’t have a good fossil record for the living coelacanth, for example. The fish may have clung to existence in deep sea haunts that either didn’t fossilize or have not been discovered yet. And in the case of Lazarus taxa that pop up after mass extinction, it may be that populations temporarily fell too low to allow for a good chance of fossilization. The fossil record is a wonderful window to view ancient life, but we need to be aware of the cracks and smudges while gazing into prehistory.

[Note:  I started this feature as “Science Word of the Day”, but it’s not daily and I want to include phrases that are more than one word. So “Sciencespeak”, it is.]


Abdala, F., Damiani, R. Yates, A., Neveling, J. 2007. A non-mammaliaform cynodont from the Upper Triassic of South Africa: a therapsid Lazarus taxon? Palaeontologia Africana. 42: 17-23

Fara, E. 2001. What are Lazarus taxa? Geological Journal. 36: 291-303

Ma, J. 2002. The history of the discovery and initial seed dissemination of Metasequoia glyptostroboides, a “living fossil”. Aliso. 21 (2): 65-75.

Ma, J. 2003. The chronology of the “living fossil” Metasequoia glyptostroboides (Taxodiaceae): A review (1943-2003). Harvard Papers in Botany. 8 (1): 9-18

Shao, G., Liu, W., Chen, J., Ma, J., Tan, Z. 2000. Zhan Wang (1911-2000). Taxon. 49 (3): 593-601

Van Roy, P., Orr, P., Botting, J., Muir, L., Vinther, J., Lefebvre, B., Hariri, K., Briggs, D. 2010. Ordovician faunas of Burgess Shale type. Nature. 465: 215-218.

Planting the Cenozoic Garden

Sixty six million years ago, a global catastrophe extinguished the non-avian dinosaurs. This is common knowledge. It’s also too narrow a view. Various forms of life disappeared in the same geologic instant – from coil-shelled ammonites to some forms of mammal – and others, for reasons as yet unknown, survived.

Plants are among the neglected of the victims and survivors. A magnolia tree does not hold the same cultural cachet as Tyrannosaurus. The post-impact “fern spike” is often cited as a symbol of wide-ranging devastation, but, outside technical journals, that’s about the extent of our attention span for paleoflora. That’s a shame. If we’re going to understand how life on Earth was so deeply wounded 66 million years ago, and how it bounced back, we should be looking more closely at the prehistoric garden.

Hot on the heels of a review summarizing the global dinosaurian picture at the end of the Cretaceous, Lund University paleobotanists Vivi Vajda and Antoine Bercovici have now assembled a view of how plants were affected by the Earth’s fifth mass extinction. Prehistoric pollen and spores tell the story.

The advantage of looking at fossil pollen, Vajda and Bercovici write, is that there’s plenty of it. That’s not only because plants produce large amounts of the reproductive material, but because pollen is also incredibly durable. If you want to see who’s living where, and how environments change through time, these microscopic plant fossils are good way to do it.

In some ways, the story of the Cretaceous plants echoes what paleontologists have found among other forms of life. The Cretaceous world was a highly-dynamic one marked by fluctuating sea levels, the further breakup of continents, and the formation of new mountain ranges. All this moving and shuffling created evolutionary pockets where new species could evolve in relative isolation, becoming restricted to their particular province. Plants proliferated and evolved according to these boundaries just as dinosaurs did.

A global view of the Late Cretaceous. Map by Ron Blakey, CC-BY-SA.
A global view of the Late Cretaceous. Map by Ron Blakey, CC-BY-SA.

Each of the pollen provinces, outlined by Vajda and Bercovici, have their own distinctive profile. In northern North America, Asia, and a few spots in South America, Late Cretaceous sediments commonly contain Aquilapollenites – pollen thought to have come from a group of plants closely related to the modern sandalwood. A neighboring province – stretching from eastern North America to the Himalayas – is dominated by pollen from a Cretaceous birch relative, while rocks from the same time in northern South America, central Africa, and India are rife with pollen from palms. Rounding out the set, a southern hemisphere swath has plenty of pollen from plants related to southern beeches and shrubs.

These were not the only plants to exist in those areas, of course, but their pollen broadly delineates differentiated patches. Paleobotanists can zoom in from there, and, as with dinosaurs, the best-studied sites on the planet document the end of the Cretaceous through the beginning of the Paleogene in western North America.

The forests that Tyrannosaurus and Triceratops knew were dominated by angiosperms – flowering plants – with some conifers, ferns, ginkgos, and cycads for good measure. Palm trees stood alongside evergreens and towered above a shrubby understory in these Late Cretaceous forests. In the aftermath of the impact 66 million years ago, however, those forests were replaced by a relatively small collection of angiosperms, a shadow of the diversity that the Edmontosaurus and kin knew.

Plants suffered extinctions just as many other forms of life did. In fact, some of them dwindle to nothing right at the K-Pg boundary are called “K-species” or “K-taxa.” In the pollen record of North America, for example, the sandalwood relative and a suite of species in seven other genera give way to species in just two genera. Overall, about 60% of plant species present in Cretaceous North America went extinct. The rest of the globe reflects a similar pattern, albeit with different species. Many pollen-producing plants either went entirely extinct or became much less abundant.

Clues from the earliest days of the Paleogene track how plant life eventually bounced back. While sites in New Zealand preserve a “fungal spike” from when mushrooms and their ilk thrived on decomposing matter under blacked-out skies, the subsequent “fern spike” records when pioneering plants – primarily ferns – quickly spread as sunlight began to return. The angiosperms, as well as some conifers, followed, but with fewer species than before. Depending on the location, plant life took between one and ten million years to recover to pre-extinction levels of diversity.

As with the animals, though, why some plants went extinct and others persisted is a mystery. Perhaps some were simply lucky enough to grow in places that were less affected by the devastation following the asteroid strike. Then again, Vajda and Bercovici point out, some researchers have suggested that plants carrying additional sets of chromosomes – or were polyploid – might have had the genetic flexibility to more quickly adapt after ecological shock.

Discerning what made a survivor isn’t just an exercise in replaying ancient history, though.

Vajda and Bercovici argue that two previous mass extinctions – roughly 251 and 200 million years ago – follow a similar pattern of a highly-diverse flora being pruned back, followed by crisis species, pioneer communities, and ecosystem recovery in sequence. Which left me to wonder if we’re going to see this pattern again. If  we’re not yet in a Sixth Extinction, we’re close, and identifying likely survivors verses vulnerable species is an essential part of conservation triage. By sifting through the past, down to the tiniest pollen grain, we can reflect on what sort of future we want to create.


Vajda, V., Bercovici, A. 2014. The global vegetation pattern across the Cretaceous-Paleogene mass extinction interval: A template for other extinction events. Global and Planetary Change. doi: 10.1016/j.gloplacha.2014.07.014

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Tomatoes Build Pesticides From The Smells Of Their Neighbours

A caterpillar bites into a single tomato plant and an entire field becomes a little deadlier.

It’s easy to underestimate what plants can do. They’re not just passive victims of animal attacks, in need of rescue through barriers and pesticides. They can produce defensive toxins to poison the creatures that try to eat them; the natural pesticides in our food far outnumber the synthetic ones we spray on them. They can also communicate with each other by releasing alarm chemicals into the air. Some of these attract parasites that kill the leaf-eating pests. Others tell neighbouring plants to start upping their own defences.

But the tomato does something different. It releases an airborne chemical that works not as an alarm, but as an ingredient. Other tomatoes can grab the substance from the air, and convert it into a toxin within their own tissues. They can turn an odour into a chemical weapon.

Koichi Sugimoto from Yamaguchi University discovered this trick after unleashing the common cutworm—a moth caterpillar—on potted tomato plants. Tomatoes can usually kill around 30 percent of these pests on their own. But Sugimoto showed that their defences become stronger if they sit downwind of other tomatoes that face a cutworm assault. If they detect the whiff of infested neighbours, they can kill almost 50 percent of their own cutworms.

This ability is the result of a single chemical called HexVic. Compared to naive tomatoes, those that are exposed to infested plants have 24 times more HexVic in their tissues, and this is one of the only substances to distinguish the two groups.

You might assume that the tomatoes make their own HexVic, after detecting an alarm chemical released by their infested peers. That’s partly true; they do make their own, but not from scratch. Their stockpile depends entirely on an ingredient called (Z)-3-hexenol, which is released by the infested plants.

Sugimoto’s team proved this by spraying tomatoes with a slightly radioactive version of (Z)-3-hexenol. The plants amassed lots of radioactive Hexvic but none of the normal kind. They were clearly building the substance from (Z)-3-hexenol in the air, rather than making it themselves.

There are many examples of animals that steal poisons from their prey, like the sea slug Glaucus which nicks the stings of jellyfish, or the tiger keelback snake that pilfers poisons from the toads it eats. But the tomatoes are doing something very different—they’re equipping each other with the building blocks of weapons. They’re like soldiers who react to enemy fire by throwing gun parts and bullets to their squadmates.

How does this defence play out in nature? Sugimoto’s team made a preliminary stab at answering this question by planting 16 tomato plants in a field outside their university. As in the lab, the tomatoes built up more HexVic if they were exposed to infested plants.

But how exactly do they convert (Z)-3-hexenol into Hexvic? And since many plants release (Z)-3-hexenol when they’re damaged by plant-eaters, do other species rely on the same defence? Could tomatoes grab chemical from other plants to build their toxic stockpiles?

Reference: Sugimoto, Matsui, Iijima, Akakabe, Muramoto, Ozawa, Uefune, Sasaki, Alamgir, Akitake, Nobuke, Galis, Aoki, Shibata & Takabayashi. 2014. Intake and transformation to a glycoside of (Z)-3-hexenol from infested neighbors reveals a mode of plant odor reception and defense. PNAS http://doi/10.1073/pnas.1320660111

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The Most Versatile Impressionist In the Forest

Ernesto Gianoli wasn’t the first person to work out his frustrations with a walk in the woods, but the motivation behind that walk—and its results—were certainly unusual.

Gianoli studies the plants of Chile’s temperate rainforests. When he goes out into the field, he usually works to a tight schedule, involving dawn-to-dusk sampling and measuring. “One day, I felt that while being engaged in these work plans, we were missing the joy of the quiet observation of nature,” he says. “I told my students that I would dedicate some hours to walk slowly across the forest, just observing. And then it happened.”

Gianoli noticed that the leaves on one particular shrub seemed to be growing from two very different stems—one much thinner than the other. He eventually realised that the thin stems actually belonged to a Boquila vine, whose leaves were exactly the same as the shrub’s. He walked on and found Boquila entwined around many different trees; in most cases, its leaves matched those of its host. It looked like a mimic, and one with many guises.

“It was astonishing,” he says. “I was familiar with the vine but I had not noticed this feature before. I walked back to the hut where the rest of my team was waiting, and told my undergraduate student Fernando Carrasco-Urra, ‘Do you want to be famous? I’ve got the idea for your thesis.’ Of course, they mocked me.”

But as Carrasco-Urra and Gianoli collected more data, the scepticism faded. Boquila’s leaves are extraordinarily diverse. The biggest ones can be 10 times bigger than the smallest, and they can vary from very light to very dark. In around three-quarters of cases, they’re similar to the closest leaf from another tree, matching it in size, area, length of stalk, angle, and colour. Boquila’s leaves can even grow a spiny tip when, and only when, it climbs onto a shrub with spine-tipped leaves.

“There are some leaf features that are too hard to copy, such as serrated leaf margins,” says Gianoli. “It is common to see cases where Boquila “did her best”, and attained some resemblance, but did not really meet the goal.”

The same vine can even mimic several trees! If it crosses from one plant to another, its leaves change accordingly.

“Even orchids, the world’s best known plant mimics, just mimic one specific model, or just share the general appearance of several similar flowers,” says Anne Gaskett from the University of Auckland. “This vine seems to mimic many specific models, depending on its host—something we’ve previously only seen in animals.”

Environmental factors like light aren’t behind these similarities. After all, Carrasco-Urra and Gianoli found very different Boquila leaves in areas with very similar light levels. They also showed that the unusual leaves only turn up when there are other plants to mimic. A Boquila vine climbing up a bare tree trunk looks exactly the same as one that’s crawling along the forest floor. It only changes when there’s a leaf around to mimic.

Why? Carrasco-Urra and Gianoli suspect that the disguises protect Boquila from hungry mouths. By climbing, the vine can already avoid plant-eaters on the ground, but the duo showed that it bears even fewer signs of damage if it climbs on a host tree rather than a leafless support. Does it just become less conspicuous, or does it gain an advantage by mimicking distasteful hosts? No one knows yet.

It’s also unclear how the vine mimics other trees, let alone so many. Australian mistletoes can mimic the trees they grow upon, but they are parasites that tap directly into their hosts. By contrast, Boquila can match hosts without any contact.

Carrasco-Urra and Gianoli suggest that they might be picking up on airborne chemicals released by other trees. We know that chemicals like these can act as alarms, which tell plants that their neighbours are in danger and to raise their own defences. Perhaps Boquila taps into these danger signals to work out which disguise to adopt.

Alternatively, the vine might be using genes from its host. There are many cases where genes have moved horizontally from one plant species to another, sometimes via a parasite or microbe. This idea is speculative and unlikely, but it is strange that Boquila takes on the guise of the nearest leaf, even if that leaf doesn’t belong to the tree that the vine has actually climbed.

Carrasco-Urra and Gianoli are now trying to solve these mysteries by testing Boquila’s abilities in experiments. They’re moving the vine from one host to another and exposing it to the smells of different hosts, to see if it changes accordingly. They also want to sequence the DNA of the vine and its hosts to see if any genes could be hopping across.

“The naturalist view should come first and the scientific approach should follow,” says Gianoli. Observation, then understanding. It’s the approach that Charles Darwin, the quintessential naturalist, used to develop his theory of natural selection. It’s the approach that Gianoli wanted to return to when he went for his walk.

Reference: Gianoli & Carrasco-Urra. 2014. Leaf Mimicry in a Climbing Plant Protects against Herbivory. Current Biology. http://dx.doi.org/10.1016/j.cub.2014.03.010

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Genetic Gift May Have Turned Ferns Into Masters of Shadow

Even in their quietest and stillest moments, forests are places of fierce competition. Sunlight is the one of the most precious commodities here, and plants jostle, circumvent, and kill each other for prime positions beneath the incoming rays. Ferns are masters of this game; they excel at growing in the shade. Fay-Wei Li from Duke University thinks that their success depends on a single moment that happened around 180 million years ago, when an ancient fern stole a gene from another plant.

Ferns are sometimes portrayed as relics of an earlier phase of plant evolution, which were outcompeted by flowering plants and relegated to the bottoms of forests. But that’s not the case. Ferns may be an ancient group (they first arose 360 million years ago), but the vast majority of living members arose much later, during the Cretaceous period. By that time, flowering plants were already dominating the world. Ferns weren’t plucky holdouts consigned to some scrapheap of existence; they diversified in the shadows of other plants.

These lineages had a tool that almost all other plants (and indeed, other ferns) lack—a light sensor called neochrome. Most plants move towards sources of light using molecules that are sensitive to blue light, although some use red-light sensors instead. But neochrome is incredibly sensitive to both blue and red. That gives ferns an advantage because blue light is largely filtered out by the upper layers of a forest, while red light penetrates more deeply. Using neochrome, ferns could ‘see’ better in a shady, flower-filled world.

But where did neochrome come from? Li decided to find out. “I love ferns and I want to know why there are so many of them,” he says. “Neochrome seemed to be a great starting point to me, so I just decided to figure out its evolutionary history.”

That was easier said than done. When Li started, there weren’t a lot of complete plant genomes on record, so he didn’t have a lot of data to work with… and what he had made no sense. “I remember walking into my advisor’s office one day and telling her my PhD is doomed because I couldn’t figure this out,” he says. Salvation came from the One Thousand Plant Project—a massive initiative to study how plants, from algae to flowers, use their genes. Suddenly, Li had data galore. He wrote a programme to analyse it, “and one night, my Macbook terminal told me that it found a neochrome-like sequence in hornworts.”

Hornworts are usually found in greasy, blue-green mats, growing in damp or humid places. They’re even older than ferns, and were among the first plants to colonise the land.

It’s possible that the common ancestor of hornworts and ferns already had neochrome, and many of its descendants—including all trees and flowers—then lost this molecule. Alternatively, both hornworts and ferns could have invented neochrome independently. But Li’s analysis showed that both of these scenarios are extremely unlikely.

The fern and hornwort versions of neochrome are clearly related and shared a common ancestor. By comparing these modern versions and working backwards, Li calculated that they diverged from each other around 179 million years ago. By contrast, the ferns and hornworts themselves split off at least 400 million years ago.

This pattern, which doesn’t apply to any other fern gene, strongly suggests that the ferns acquired the gene for neochrome directly from hornworts. After that, the gene seems to have repeatedly hopped between different fern lineages.

These “horizontal gene transfers” are everyday events for bacteria, which seem to trade DNA with the same ease that we exchange emails. They’re much rarer in plants and animals, and many reported examples have been met with scepticism. But Li’s study has certainly won over Jeffrey Palmer from Indiana University. “I’ve read their paper closely, and I think their evidence is very strong and convincing,” he says.

Palmer is more measured about the idea that gaining neochrome allowed ferns to diversify in the shadow of flowers—it’s a plausible idea, but not one that’s been proven yet. If it was, “it would be the most significant horizontal transfer yet discovered in plants,” he says. Most transferred genes, including some that Palmer has discovered, don’t do very much. But neochrome “had the potential to really shake up fern physiology in a big way, and be really adaptive.”

Li is now looking for other horizontally transferred fern genes, to see if neochrome is exceptional or just part of a general pattern. And he’s also studying neochrome in hornworts to see what the gene does in its original owners.

Reference: Li, Villarreal, Kelly, Rothfels, Melkonian, Frangedakis, Ruhsam, Sigel, Der, Pittermann, Burge, Pokorny, Larsson, Chen, Weststrand, Thomas, Carpenter, Zhang, Tian, Chen, Yan, Zhu, Sun, Wang, Stevenson, Crandall-Stotler, Shaw, Deyholos, Soltis, Graham, Windham, Langdale, Wong, Mathews & Pryer. 2014. Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns. PNAS http://dx.doi.org/10.1073/pnas.1319929111

More on horizontal gene transfer: