Trees Talk

Around 90% of terrestrial plants are in mutually-beneficial relationships with fungi. “Mycorrhiza” is the term coined by the 19th-century German biologist Albert Bernard to describe these relationships, in which the fungus colonizes the roots of the plant.

Here, plants provide fungi with food in the form of carbohydrates and the fungi help the plants suck up water, and nutrients like phosphorus and nitrogen, via their mycelia. Since the 1960s, it was known that mycorrhizae help individual plants to grow but now after multiple experiments it has also been proven that they help in the collective growth of multiple plants.

icebergs floating in the water near a body of water

These networks not only communicate information in the form of nutrients but also help boost immunity and transfer toxic chemicals. Because a huge network of fungi grows on the plant body, the plant treats it like a foreign body and prepares for an attack before realizing that they can mutually exist together. This alerts the immune system and keeps it ready for any future combat, just like in the human body, where there may be no chance of a mutual relationship. This is called “priming”.

Back in 1997, Suzanne Simard of the University of British Columbia in Vancouver found the first evidence of this network. She showed that Douglas Fir and Paper Birch trees can transfer carbon between them via mycelia. Later, others went further to show that plants can exchange nitrogen and phosphorus as well.

Simard also believes larger trees help out small, younger ones and this is how many seedlings survive. In her study, seedlings in the shade, which were likely to be short of food got more carbon from donor trees.

She also found that in the case of a tree belonging to the same species, it was favored with more nutrients than others and also was supplied earlier than the rest. This shows that trees not only communicate but do so in a directed manner, by recognizing and preferring members of their own kin over others.

“These plants are not really individuals in the sense that Darwin thought they were individuals competing for survival of the fittest. In fact, they are interacting with each other, trying to help each other survive,” said Simard in the 2011 documentary Do Trees Communicate?

tree with brunch and green leaves during sunset — Photo by Pixabay on Pexels.com

In another research of 2010, Ren Sen Zeng of South China Agricultural University in Guangzhou found that plants release chemical signals into the mycelia that warn their neighbors of harmful diseases as well. In his experiment, he grew pairs of tomato plants some of which were allowed to form fungal networks while some did not. Once the fungal networks had formed, the leaves of one plant in each pair were sprayed with a fungus that caused early blight disease.

Air-tight plastic bags were put over the parts above the ground to prevent any above-ground chemical signaling between the plants. After 65 hours, Zeng sprayed the second plant in each pair with the same fungus and found that they were much more resistant, and had significantly lower levels of damage if they had mycelia.

“We suggest that tomato plants can ‘eavesdrop’ on defense responses and increase their disease resistance against a potential pathogen,” wrote Zeng and his colleagues wrote proving that mycelium helps plants defend themselves as well.

However, this internet too is prone to cybercrimes. Some plants steal from each other. Plants that do not have chlorophyll and are not able to produce their own food, such as the phantom orchid, get the carbon they need from nearby trees via this internet. Plants usually compete with their neighbors for resources like water and light and to win this battle, some release chemicals that can harm their rivals.

This is common in trees like acacias, sugarberries, American sycamores and Eucalyptus. Scientists are skeptical about the effectiveness of this process though because most harmful chemicals are likely to be absorbed by soil, or broken down by microbes, before they could travel far.

In 2011, chemical ecologist Kathryn Morris and her colleagues set out to test this theory in golden marigolds and found that in the marigolds with the mycelium, levels of the toxins sprayed were higher than in those without. This proved that mycelia really did transport toxins as well. “These experiments show the fungal networks can transport these chemicals in high enough concentrations to affect plant growth,” said Morris.

“These fungal networks make communication between plants, including those of different species, faster, and more effective. We don’t think about it because we can usually only see what is above ground. But most of the plants you can see are connected below ground, not directly through their roots but via their mycelial connections,” Morris added.

So, in true sense a forest is not made by individuals but is instead an interconnected community; much like a family where the elder ones take care of the younger siblings and make room for newer members and pamper them with more love and care.

So, if we grow a forest we need not worry much about its well-being. It is used to taking care of itself and its family. All we need to do is give them the space and the opportunity by not interfering in its natural process. Hence, unlike what most think, trees do talk !

low angle shot photography of green trees — Photo by Felix Mittermeier on Pexels.com

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