Plants and Trees Communicate Through an Unseen Web

Plants can even ward off invaders through “Earth’s natural internet.”

 

Your typical forest is doing more than meets the eye.

Ever borrow something from a friend or neighbor? You gossip while there too, right? Perhaps even align yourselves against a common enemy. The “Wood wide web,” can do all of this for plants. Fungi are made up of tiny threads called mycelium. These travel underground, connecting the roots of different plants in an area, even different species, together, allowing them to communicate and so much more. Some researchers say the trees of the forest and the mushrooms we find growing next to them are so interconnected, that it is hard for them to see trees as individual entities any longer.


Though this may sound like news to some, indications of “Earth’s natural internet” go back to the 19th century, beginning with German biologist Albert Bernard Frank. He is the first to discover a symbiotic relationship between fungal colonies and the roots of plants. Frank created the term "mycorrhiza" to describe this symbiosis. Today we know that approximately 90% of all land-based plants are connected through what is called the mycorrhizal network.

Fungi and trees are so interconnected, some scientists believes they should not be viewed as separate organisms.

Since the 1960s we’ve known that fungi aid in plant growth. Since then, scientists have learned that they also help plants locate water and provide certain nutrients through mycelia strands around their roots. The fungal networks protect plants from infection too, by providing protective compounds, stored in the roots, which are triggered should the plant be attacked. This phenomenon, called “priming,” makes the immune system of the plant far more effective. In return, plants feed their fungi carbohydrates on a consistent basis.

Besides defense, it also serves as a communication network, connecting even to plants which are far away. Paul Stamets first had the idea of such a network in the 1970s, while studying fungi under an electron microscope. He found that there were startling similarities between the precursor to the internet, the US defense department’s ARPANET, and these fungal networks. Yet, it took decades of research to uncover the sheer breadth of the phenomenon. Other scientists have since likened it to an animal’s nervous system.

In 1983, two studies proved that poplars and sugar maple trees warn each other about worrisome insects. When one tree becomes infested, it warns others who begin producing anti-insect chemicals, to protect against attack. These signals are sent through the air. Even then, the splinter group of scientists studying this phenomenon were for decades waved away. Since the late 90’s however, such researchers have proven that trees transfer carbon, nitrogen, phosphorus, and other nutrients, back and forth via mycelia. Today, though only a scant few study it, the phenomenon is no longer in doubt.

Mycorrhizal threads. Photo by The Alpha Wolf CC-BY-SA-3.0 via Wikimedia Commons

Suzanne Simard of the University of British Columbia discovered nutrient exchanges between Douglas fir trees and paper birches. She believes it goes even farther than this. Simard says that small, younger trees are helped through the network by larger, older ones. Without such aid, she said, seedlings wouldn’t stand a chance. Simard found in one study that food strapped seedlings stuck in the shade received carbon from nearby trees to help them along.

Of course, Simard isn’t suggesting that plants have consciousness or that they are individuals in any sense. But they are interacting and helping one another survive. Other experts warn that although we are aware of such exchanges, to what extent they occur remains unclear.

In 2010, Ren Sen Zeng, a researcher at South China Agricultural University, proved that plants communicate through the mycelia network. Zeng and colleagues found that when infected with blight, tomato plants release a chemical signal to warn others nearby. These plants also “eavesdrop” on neighbors, to determine when to build up their defenses against oncoming pathogens. A 2013 study found that broad beans also signaled neighbors through the fungal network, this time due to an aphid infestation. But not all interactions are helpful. There is a dark side to the mycorrhizal network, too.

Mycelium. Photo by Rob Hille [CC BY-SA 3.0)], via Wikimedia Commons

A phantom orchid for instance cannot produce its own energy. Instead, it steals carbon from trees close by in order to survive, accessing the nutrients via the mycelia threads connecting them. Other orchids, known as “mixotrophs” can photosynthesize, but steal from others when it suits them. Plants also at times compete for resources such as light and water. When this occurs, some release toxins to slow their competitors encroachment in a process is called, "allelopathy." Certain species of Eucalyptus, , American sycamores, acacias, and sugarberries are known to do this. The chemicals they release travel the network and block nearby plants from establishing themselves, or reduce the number of friendly microbes at their roots to impede their opponent’s growth.

Some experts theorize that animals may be taking advantage of the fungal network for their own ends. The same chemicals that bring helpful fungi and bacteria to a plant’s roots might also signal worms and other harmful organisms looking for a snack. But this theory to date hasn’t been tested. Some say the fungal network gives us another example of how interconnected all life on Earth actually is and how each organism depends on another and in turn is depended upon. It also makes us question whether such actions constitute behavior, and what motivated plants to link up to begin with, and for fungi to lend a hand in the endeavor.

To learn more about how plants communicate click here: 

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Image source: Vaccaro et al, 2020/Harvard Medical School
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We don't have to tell you what it feels like when you don't get enough sleep. A night or two of that can be miserable; long-term sleeplessness is out-and-out debilitating. Though we know from personal experience that we need sleep — our cognitive, metabolic, cardiovascular, and immune functioning depend on it — a lack of it does more than just make you feel like you want to die. It can actually kill you, according to study of rats published in 1989. But why?

A new study answers that question, and in an unexpected way. It appears that the sleeplessness/death connection has nothing to do with the brain or nervous system as many have assumed — it happens in your gut. Equally amazing, the study's authors were able to reverse the ill effects with antioxidants.

The study, from researchers at Harvard Medical School (HMS), is published in the journal Cell.

An unexpected culprit

The new research examines the mechanisms at play in sleep-deprived fruit flies and in mice — long-term sleep-deprivation experiments with humans are considered ethically iffy.

What the scientists found is that death from sleep deprivation is always preceded by a buildup of Reactive Oxygen Species (ROS) in the gut. These are not, as their name implies, living organisms. ROS are reactive molecules that are part of the immune system's response to invading microbes, and recent research suggests they're paradoxically key players in normal cell signal transduction and cell cycling as well. However, having an excess of ROS leads to oxidative stress, which is linked to "macromolecular damage and is implicated in various disease states such as atherosclerosis, diabetes, cancer, neurodegeneration, and aging." To prevent this, cellular defenses typically maintain a balance between ROS production and removal.

"We took an unbiased approach and searched throughout the body for indicators of damage from sleep deprivation," says senior study author Dragana Rogulja, admitting, "We were surprised to find it was the gut that plays a key role in causing death." The accumulation occurred in both sleep-deprived fruit flies and mice.

"Even more surprising," Rogulja recalls, "we found that premature death could be prevented. Each morning, we would all gather around to look at the flies, with disbelief to be honest. What we saw is that every time we could neutralize ROS in the gut, we could rescue the flies." Fruit flies given any of 11 antioxidant compounds — including melatonin, lipoic acid and NAD — that neutralize ROS buildups remained active and lived a normal length of time in spite of sleep deprivation. (The researchers note that these antioxidants did not extend the lifespans of non-sleep deprived control subjects.)

fly with thought bubble that says "What? I'm awake!"

Image source: Tomasz Klejdysz/Shutterstock/Big Think

The experiments

The study's tests were managed by co-first authors Alexandra Vaccaro and Yosef Kaplan Dor, both research fellows at HMS.

You may wonder how you compel a fruit fly to sleep, or for that matter, how you keep one awake. The researchers ascertained that fruit flies doze off in response to being shaken, and thus were the control subjects induced to snooze in their individual, warmed tubes. Each subject occupied its own 29 °C (84F) tube.

For their sleepless cohort, fruit flies were genetically manipulated to express a heat-sensitive protein in specific neurons. These neurons are known to suppress sleep, and did so — the fruit flies' activity levels, or lack thereof, were tracked using infrared beams.

Starting at Day 10 of sleep deprivation, fruit flies began dying, with all of them dead by Day 20. Control flies lived up to 40 days.

The scientists sought out markers that would indicate cell damage in their sleepless subjects. They saw no difference in brain tissue and elsewhere between the well-rested and sleep-deprived fruit flies, with the exception of one fruit fly.

However, in the guts of sleep-deprived fruit flies was a massive accumulation of ROS, which peaked around Day 10. Says Vaccaro, "We found that sleep-deprived flies were dying at the same pace, every time, and when we looked at markers of cell damage and death, the one tissue that really stood out was the gut." She adds, "I remember when we did the first experiment, you could immediately tell under the microscope that there was a striking difference. That almost never happens in lab research."

The experiments were repeated with mice who were gently kept awake for five days. Again, ROS built up over time in their small and large intestines but nowhere else.

As noted above, the administering of antioxidants alleviated the effect of the ROS buildup. In addition, flies that were modified to overproduce gut antioxidant enzymes were found to be immune to the damaging effects of sleep deprivation.

The research leaves some important questions unanswered. Says Kaplan Dor, "We still don't know why sleep loss causes ROS accumulation in the gut, and why this is lethal." He hypothesizes, "Sleep deprivation could directly affect the gut, but the trigger may also originate in the brain. Similarly, death could be due to damage in the gut or because high levels of ROS have systemic effects, or some combination of these."

The HMS researchers are now investigating the chemical pathways by which sleep-deprivation triggers the ROS buildup, and the means by which the ROS wreak cell havoc.

"We need to understand the biology of how sleep deprivation damages the body so that we can find ways to prevent this harm," says Rogulja.

Referring to the value of this study to humans, she notes,"So many of us are chronically sleep deprived. Even if we know staying up late every night is bad, we still do it. We believe we've identified a central issue that, when eliminated, allows for survival without sleep, at least in fruit flies."

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