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5 Ways Plants Communicate

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You may not think of plants as particularly chatty or active organisms, but they’re not as passive as they might seem. Plants can’t run away, so they have to develop other strategies to stay alive, as James Cahill, an environmental plant ecologist at the University of Alberta, explains in “What Plants Talk About,” a documentary from the PBS show NATURE. They’ve evolved the use of chemicals to communicate with insects and each other in order to thrive. Here are five behaviors that show how active plants can be. 

1. Plants can call for help

When you inhale the sweet smell of freshly mown grass or cut flowers, what you’re actually smelling is the plant’s distress call. “It’s the plant's way of crying out for help,” Cahill says. The scent attracts insects that will eat the pests currently munching on their plant-bodies. For instance, the wild tobacco plant can identify a hornworm caterpillar by its saliva. When attacked by this caterpillar, the tobacco plant emits a chemical signal that appeals to the insect’s enemies. Within hours, caterpillar predators like the big-eyed bug show up, ideally driving the pest away. 

2. Plants can eavesdrop

Plants can eavesdrop on the chemical signals of their brethren, and sometimes respond to another plant’s SOS cry by ramping up their own defenses proactively, knowing that a hungry insect is nearby. 2013 review found 48 studies support the idea that plants increase their defenses after their neighbors are damaged. For instance, when wounded by a hornworm, sagebrush releases defensive proteins called trypsin proteinase inhibitors (TPIs), which prevent the insect from digesting protein and stunt its growth. When neighboring plants—even other species—are exposed to the chemical signals of damaged sagebrush, they begin readying their defenses. Wild tobacco, scientists found, begins prepping to make these TPIs when it senses a distress call from sagebrush, giving it a head start on defending itself if the caterpillar comes calling. 

3. Plants can defend their territory 

Plants compete with each other for sunlight, jostling for position among their neighbors. They also can push out competition in other ways. The invasive knapweed plant—native to Eastern Europe but wrecking havoc on U.S. grasslands—has roots that release certain chemicals to help the plant take in nutrients from the soil. Those same chemicals also kill off native grasses. Thus, the knapweed ends up taking over large territories and killing off its competitors, much like some animals do. Some plants, however, have formed a defense. Lupin roots secrete oxalic acid, which forms a protective barrier against the toxic chemicals given off by knapweed. Lupin can even protect other plants in its vicinity from falling prey to the invasive species. 

4. Plants can recognize their siblings 

Plants can sense when other plants are growing around them. This helps them compete for resources like sunlight, growing more if another plant is shading them, for instance. But like animals, they tend to recognize and support their kin. In an experiment with sea rocket, a plant that often grows close together with its siblings, plants that were grown in pots with relatives had more restrained root growth than plants grown with random strangers. The plants in the stranger condition grew more roots in order to better compete for food, whereas the sibling plants were more considerate of each other’s needs. Further experiments showed that sibling plants recognize each other via chemical signals.  

5. Plants can communicate with mammals

Plants go out of their way to attract more than just insects. A carnivorous pitcher plant native to Borneo has evolved to hijack bat communication systems, turning the bats’ echolocation to its advantage. According to a new study in Current Biology, Nepenthes hemsleyan has a concave structure that is specially suited to reflect bat echolocation, helping the bats find the plant. The bats roost in the pitcher plant, and provide important nutrients by way of the bat guano that gets distributed in the soil nearby.   

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environment
Great Britain's Last Snow Patch Is About to Disappear Completely for the First Time in a Decade

Until recently, it was easy to find snow in Great Britain at any time of the year—you just had to know where to look. In previous Septembers, the island has been home to as many as 678 snow patches, residual pockets of snow and ice whose climates and topographies keep them frozen through the summer. This year, though, only two of Britain's snow patches have survived the summer. And the island is now on track to be completely snowless by the end of the season, Atlas Obscura reports.

Snow patches vary in size and durability, with some melting completely by late summer and others remaining a permanent fixture of the landscape. Garbh Choire Mor—a steep glacial depression on top of Scotland's third-highest mountain, Braeriach—contains two of the oldest snow patches in Britain, known as the Pinnacles and the Sphinx. The Pinnacles snow patch dissolved into a puddle earlier this month, and the Sphinx snow patch, the last surviving snow patch in Great Britain, is expected to do the same in the next few days.

Scotland experienced uncharacteristically hot weather this summer, with temperatures creeping into the low 90s as early as May. But more significant than the sweltering summer was the dry winter that preceded it. Below-average snowfall last year meant this year's snow patches were already smaller than usual when temperatures started heating up. If the Sphinx snow patch does vanish before winter arrives, it will mark the first time in over a decade and just the sixth time in the last 300 years that England, Scotland, and Wales are without a single patch of snow.

The Sphinx snow patch, though currently a measly version of its previous self, is still visible for now. But Iain Cameron, a veteran "snow patcher" who writes an annual report on snow for the UK's Royal Meteorological Society, says it could be gone as soon as Wednesday, September 20.

He's currently camped out on Garbh Choire Mor, waiting to document the patch's final moments. You can follow his updates on Twitter.

[h/t Atlas Obscura]

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The King of Kong © Jim Naughten. Courtesy of Michael Hoppen Gallery
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geography
The Mountains of Kong: The Majestic West African Range That Never Existed
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The King of Kong © Jim Naughten. Courtesy of Michael Hoppen Gallery

If you look closely at a 19th century map of Africa, you’ll notice one major way that it differs from contemporary maps, one that has nothing to do with changing political or cartographical styles. More likely than not, it features a mountain range that no longer appears on modern maps, as WIRED explains. Because it never existed in the first place.

A 19th century map of West Africa
From Milner's Descriptive Atlas, 1850

The “Mountains of Kong” appeared on almost every major commercial map of Africa in the 1800s, stretching across the western part of the continent between the Gulf of Guinea and the Niger River. This mythical east-west mountain range is now the subject of an art exhibition at London’s Michael Hoppen Gallery.

In "Mountains of Kong," stereoscopic images by artist Jim Naughten—the same format that allowed Victorians with wanderlust to feel like they’d seen the world—reveal his view of the world of wildlife that might have existed inside the imagined mountains. As the gallery describes it, “he imagines a fictitious record made for posterity and scientific purposes during an expedition of the mountain range.” We’ve reproduced the images here, but to get the full effect, you’ll have to go to the gallery in person, where you can view them in 3D with a stereoscope (like the ones you no doubt played with as a kid).

Toucans fight a snake in two almost-identical side-by-side images.
The Toucans © Jim Naughten. Courtesy of Michael Hoppen Gallery

Naughten created the images by taking two photographs for each, and moving the camera over some 3 inches for the second photo to make a stereoscopic scene. The landscapes were created by shooting images of Scottish and Welsh mountains and dioramas in natural history museums, using Photoshop to change the hues of the images to make them seem more otherworldly. His blue-and-pink-hued images depict fearsome apes, toucans sparring with snakes, jagged peaks, and other scenes that seem both plausible and fantastical at the same time.

The Mountains of Kong appeared in several hundred maps up until the 20th century. The first, in 1798, was created by the prominent geographer James Rennell to accompany a book by Scottish explorer Mungo Park about his first journey to West Africa. In it, Park recounts gazing on a distant range, and “people informed me, that these mountains were situated in a large and powerful kingdom called Kong.” Rennell, in turn, took this brief observation and, based on his own theories about the course of the Niger River, drew a map showing the mountain range that he thought was the source of the river. Even explorers who later spent time in the area believed the mountains existed—with some even claiming that they crossed them.

Two colobuses stand in a tree on a mountaintop.
The Colobus © Jim Naughten. Courtesy of Michael Hoppen Gallery

The authority of the maps wasn’t questioned, even by those who had been to the actual territory where they were depicted as standing. Writers began to describe them as “lofty,” “barren,” and “snow-covered.” Some said they were rugged granite peaks; others described them as limestone terraces. In almost all cases, they were described as “blue.” Their elevation ranged from 2500 feet to 14,000 feet, depending on the source. Over the course of the 19th century, “there was a general southward ‘drift’ in the location,” as one pair of scholars put it.

Though geographers cast some doubt on the range’s existence as time went on, the Mountains of Kong continued to appear on maps until French explorer Louis-Gustave Binger’s Niger River expedition between 1887 and 1889, after which Binger definitively declared their nonexistence.

By 1891, the Mountains of Kong began dropping off of maps, though the name Kong still appeared as the name of the region. By the early 20th century, the mountains were gone for good, fading into the forgotten annals of cartographic history.

[h/t WIRED]

All images courtesy Michael Hoppen Gallery.

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