It's like a little magnetic "nom, nom."
- Venus flytrap leaves shut in response to physical touch, salt water, or thermal stimuli.
- A team of scientists from Berlin have captured the magnetic charge that accompanies the closing of the plant's trap.
- Incredibly sensitive, non-invasive atomic magnetometers picked up the elusive signal.
For many children, the revelation that there's such a thing as a Venus Flytrap, Dionaea muscipula, is an amazing moment. The choppers of the sneaky plant predators are like something out of a fairy tale gone wrong. Adults can't help but be fascinated by them too, and now scientists at Johannes Gutenberg University Mainz (JSU) and the Helmholtz Institute Mainz in Germany have discovered something new that's surprising about these little demons: Every time they entrap prey, they give off a measurable magnetic charge.
"We have been able to demonstrate that action potentials in a multicellular plant system produce measurable magnetic fields, something that had never been confirmed before," says lead author Anne Fabricant.
Guilt as magnetically charged
The plants' bivalved snap trap (left), side view of a destained trap lobe (right)
Credit: Fabricant, et al./Scientific Reports
According to Fabricant, the finding isn't that much of a shock: "Wherever there is electrical activity, there should also be magnetic activity," she tells Live Science. And it is electrical activity in the form of action potentials that trigger its maw—really a pair of leaf lobes—to close when a hapless bug lands inside them, attracted by the nectar with which the plants bait their trap.
Along the inner surfaces of the lobes are trichomes, hair-like projections that cause the trap to close when they're disturbed by prey. One touch of a trichome is unlikely to cause the trap to shut — perhaps a mechanism that helps the plant avoid wasting energy on false alarms. A couple of touches, though, and it's chow time. The lobes come together as the bristles at their edges intertwine to help contain the prey. As the traps compress the trapped insect, its own secretions such as uric acid cause the trap to shut even more tightly, and then digestion begins.
In any event, just because the JSU researchers had reason to suspect the plant would give off a magnetic charge, catching it doing so was not a simple task.
Reading the Venus flytrap's magnetic output
Average action potential and corresponding magnetic signals
Credit: Fabricant, et al./Scientific Reports
"The problem," says Fabricant, "is that the magnetic signals in plants are very weak, which explains why it was extremely difficult to measure them with the help of older technologies." Still, where there's a will: "You could say the investigation is a little like performing an MRI scan in humans."
It's not just trichome flicks that trigger the trap — it will also close if triggered by salt-water, or with an application of either hot or cold thermal energy. The researchers applied heat via a purpose-built Peltier device that wouldn't introduce any background magnetic noise to mask or overwhelm the faint magnetic signal they were seeking. For the same reason, the experiments were conducted in a magnetically shielded room at Physikalisch-Technische Bundesanstalt (PTB) in Berlin.
The researchers used atomic magnetometers to measure the planets magnetic charges. The atomic magnetometer is a glass cell containing a vapor of rubidium atoms. When the traps were triggered, the magnetic charges released changed the spins of the atoms' electrons.
The researchers picked up magnetic signals at an amplitude of up to 0.5 picoteslas. "The signal magnitude recorded is similar to what is observed during surface measurements of nerve impulses in animals," says Fabricant. It's over a million times weaker than the Earth's own magnetic field.
Other researchers have detected magnetic charges coming the firing of animal nerves — including within our own brain. The phenomenon is referred to as "biomagnetism." Since other plants have action potentials, they may also generate biomagnetism, though less research has been done on them.
It's to other plants that the attention of the JSU team now turns, as they go looking for even smaller magnetic charges from other species. In addition to providing new understanding of nature's use of electricity, non-invasive detection technologies such as the one employed by the group could one day be utilized for more insightful monitoring of crops as they respond to thermal, pest, and chemical influences.
University of Tokyo scientists observe predicted quantum biochemical effects on cells.
We know at this point that there are species that can navigate using the Earth's magnetic field. Birds use this ability in their long-distance migrations, and the list of such species keeps getting longer, now including mole rats, turtles, lobsters, and even dogs. But exactly how they can do this remains unclear.
Scientists have for the first time observed changes in magnetism prompting a biomechanical reaction in cells. And if that's not cool enough, the cells involved in the research were human cells, lending support to theories that we ourselves may have what it takes to get around using the planet's magnetic field.
The research is published in PNAS.
The phenomenon observed by scientists from the University of Tokyo matched the predictions of a theory put forward in 1975 by Klaus Schulten of the Max Planck Institute. Schulten proposed the mechanism through which even a very weak magnetic field—such as our planet's—could influence chemical reactions in their cells, allowing birds to perceive magnetic lines and navigate as they seem to do.
Shulten's idea had to do with radical pairs. A radical is a molecule with an odd number of electrons. When two such electrons belonging to different molecules become entangled, they form a radical pair. Since there's no physical connection between the electrons, their short-lived relationship belongs in the realm of quantum mechanics.
Brief as their association is, it's long enough to affect their molecules' chemical reactions. The entangled electrons can either spin exactly in sync with each other, or exactly opposite each other. In the former case, chemical reactions are slow. In the latter case, they're faster.
Researchers Jonathan Woodward and Noboru Ikeya in their lab
Credit: © Xu Tao, CC BY-SA
Cryptochromes and flavins
Previous research has revealed that certain animal cells contain cryptochromes, proteins that are sensitive to magnetic fields. There is a subset of these called "flavins," molecules that glow, or autofluoresce, when exposed to blue light. The researchers worked with human HeLa cells (human cervical cancer cells), because they're rich in flavins. That makes them of special interest because it appears that geomagnetic navigation is light-sensitive.
When hit with blue light, flavins either glow or produce radical pairs — what happens is a balancing act in which the slower the spin of the pairs, the fewer molecules are unoccupied and available to fluoresce.
HeLa cells (left), showing fluorescence caused by blue light (center), closeup of fluorescence (right)
For the experiment, the HeLa cells were irradiated with blue light for about 40 seconds, causing them to fluoresce. The researchers' expectations were that this fluorescent light resulted in the generation of radical pairs.
Since magnetism can affect the spin of electrons, every four seconds the scientists swept a magnet over the cells. They observed that their fluorescence dimmed by about 3.5 percen each time they did this, as shown in the image at the beginning of this article.
Their interpretation is that the presence of the magnet caused the electrons in the radical pairs to align, slowing down chemical reactions in the cell so that there were fewer molecules available for producing fluorescence.
The short version: The magnet caused a quantum change in the radical pairs that suppressed the flavin's ability to fluoresce.
"The joyous thing about this research is to see that the relationship between the spins of two individual electrons can have a major effect on biology."
He notes, "We've not modified or added anything to these cells. We think we have extremely strong evidence that we've observed a purely quantum mechanical process affecting chemical activity at the cellular level."
New research sees dogs checking a North-South axis on their way home.
- As dogs navigate, they appear to be using the Earth's magnetic fields.
- 170 dogs orient themselves to north and south as they plot shortcuts back to their people.
- Dogs join the growing number of magnetism-sensitive animals.
It's been known for a while that some animals — migratory birds, mole rats, and lobsters among them — use the Earth's magnetic fields to navigate. There's even some evidence suggesting we do, too. In 2013, zoologist Hynek Burda found that dogs tend to poop and pee along a north-south axis, although at least some dogs (including our own Lulu) don't agree. New research indicates that dogs also orient themselves to the Earth's magnetic field as they invent shortcuts to get from place to place.
The research comes from Kateřina Benediktová of the Czech University of Life Sciences Prague — Burda is her PhD adviser — and is published in eLife.
Guessing the secrets of canine navigators
That dogs have excellent navigational talents is nothing new. The study recalls "messenger dogs" that were relied on during World War I to ferry sensitive communiqués back and forth across battle lines. In addition, of course, hunting dogs, or "scent hounds," have long exhibited the ability to return to their owners' positions, and previous studies have shown that they often devise new return routes, as opposed to simply retracing their steps. How they do this has been a bit mysterious, as the study notes: "Dogs often homed using novel routes and/or shortcuts, ruling out route reversal strategies, and making olfactory tracking and visual piloting unlikely."
In trying to figure out how dogs do what they do, researchers have divided their methods into three possible modes:
- tracking — following their own scent trail back to their point of origin
- scouting — searching for a new, shorter way back to their point of origin
- visual piloting — using landmarks to find their way back
Benediktová's research began when she put video cameras and GPS trackers on four dogs, took them out into the forest, and set them loose. As might be expected, they took off in pursuit of some interesting scent. All of the dogs eventually returned. She mapped the collected GPS data, seeing runs of both tracking and scouting.
However, when she showed her maps to Burda, he noticed something else. Just before scouting their way back, the dogs did something odd: They ran for roughly 20 meters along a precise north-south axis, as if orienting themselves, before returning to Benediktová. Without some form of magnetic sensitivity, this would not be possible.
Image source: Benediktová, et al
Testing the theory
A sample of four dogs is hardly definitive, so student and advisor developed a larger study involving 27 dogs who were taken on several hundred scouting trips over the course of three years. The dogs were typically taken to locales with which they had no familiarity, and the researchers avoided tipping off the canines with any navigational clues including the avoidance of situations in which wind could carry their scent toward the dogs. The researchers also hid after releasing their charges to make sure they weren't visible to the pooches.
In the end, the researchers documented 223 scouting runs in which the dogs averaged a return to their points of origin of about 1.1 kilometers (around 0.7 miles).
In 170 of these runs, the dogs did indeed repeat the smaller sample's behavior, running about 20 meters along a north-south axis. Just as intriguingly, it was these dogs who found the fastest, most direct route back. "I'm really quite impressed with the data," biologist Catherine Lohmann of the University of North Carolina, Chapel Hill, who was not involved in the study, tells Science.
Burda considers the dogs' seeming reliance on their north-south jog to be pretty convincing: "It's the most plausible explanation."
Proving the theory
Commenting on the research, dog behaviorist Adam Miklósi at Eötvös Loránd University tells Science, "The problem is that in order to 100% prove the magnetic sense, or any sense, you have to exclude all the others."
Given the difficulties of doing that, Benediktová and Burda intend to test their hypothesis from the other direction, seeing if they can confuse dogs' magnetnoreception by placing magnets on their collars and repeating the tests — if they no longer do their little north-south jog, a reliance on the Earth's magnetic field would look even more likely.
You won't notice much of a difference unless you're north of the 55th parallel, though.
- Magnetic north has recently been moving north from Canada to Russia in a cold hurry.
- It's moving about 33 miles a year instead of the usual 7 miles.
- World navigation models had to updated ahead of schedule to catch up with it.
If you're reading this as you travel the arctic, odds are you're probably already a bit confused. Your compass has been, well, strange, lately. That's because magnetic north has been moving. Quickly. It's never been stationary, but recently it's been moving around 485 feet northward toward Siberia every day. That's about 33 miles per year, as opposed to the average 7 miles a year between 1831 and the 1990s, when its pace quickened.
Fortunately, experts say that if you're south of the 55th parallel, you won't notice much of a difference. However, for national defense agencies, commercial airlines, and others that rely on knowing what their compasses are pointing at, it's a much bigger deal. That's why the World Magnetic Model — a set of online reference calculators, software, and technical details — had to be updated recently ahead of schedule instead of waiting for the next planned revision in 2020.
North, north, and north
Image source: Pyty / Shutterstock
There are actually three flavors of north, and they're all in different places.
- Magnetic north — is defined as the location on the Earth's surface where all of its magnetic lines point straight downward. If you look at a compass while you're there, the needle attempts to dip down; that's why it's also called the "dip pole." Magnetic north is always on the move in response to the constant motion of electrical charges in the Earth's liquid outer mantle, which produces Earth's magnetic field.
- Geomagnetic north — is the northern focus of the Earth's magnetosphere, up in the stratosphere. It moves, too, but not nearly as much, since shifts in the Earth's magnetic field are more smoothed-out up there than on the ground. Its location is pretty stable, located above and off the northwest coast of Greenland.
- True north, or geographic north — is the northern terminus of our lines of longitude. It's located in the middle of the Arctic Ocean.
What’s the hurry?
Image source: Johan Swanepoel / Shutterstock
The suddenly accelerating movement of magnetic north has scientists wondering what's up — not because there's any danger we're aware of — because its behavior is one of the few opportunities they have to catch a glimpse of the dynamics inside the earth's molten outer core.
The most prominent theory is that the speed-up is being driven by, as Nature puts it, "liquid iron sloshing within the planet's core." Giant streams of molten iron and nickel continually twist and swirl in the outer core, a pressure cooker that can reach 9,000° F in temperature. The iron is the source of the magnetic fields that comprise the Earth's magnetosphere. The magnetosphere is the barrier that keeps us protected from destructive ultraviolet solar radiation — its existence keeps Earth habitable. Planets with no magnetic barrier are unable to hold onto their atmosphere. Mars lost its magnetosphere 4.2 billion years ago.
Geophysicist Phil Livermore made the case at an American Geophysical Union meeting in Fall 2018 that what we're seeing is the latest action in an ongoing tug of war between two magnetic fields down in the swirling outer core. One is under Siberia, and one is under Canada. Historically, the Canadian field has been winning, keeping magnetic north in Canada. However, there's been a shift, he tells National Geographic, "The Siberian patch looks like it's winning the battle. It's sort of pulling the magnetic field all the way across to its side of the geographic pole."
Some scientists think that the acceleration may be an early sign that Earth's magnetic poles are about to flip, something that happens every every 200,000 to 300,000 years. Others see no evidence of that. Plus, flips occur over thousands of years, so there'd be no cause for alarm anyway.
Keeping an eye on magnetic north
The position of magnetic north is tracked by the European Space Agency's three Swarm satellites orbiting the Earth about 15 times a day — the satellites' readings are continually checked against ground readings to assess the pole's movements. Every five years, until now, at least, scientists have updated the math in the World Magnetic Model, whose goal is to "ensure safe navigation for military applications, commercial airlines, search and rescue operations, and others operating around the North Pole."
Given how things like this tend to play out over geologic time, it would surprise no one if more frequent model updates will be needed going forward.