Recent developments in biology are changing the way we look at woodlands and the organisms that live within them. Trees are often considered passive creatures that take whatever they’re given. Perhaps it has something to do with the scale at which they conduct their lives (oaks don’t reach fully-grown adulthood until they’re one hundred and twenty). New work is shining light on just how active trees and other plants are and dispelling the myth of plants being more object than organism.
Over ninety percent of plants forge connections to mycelium, a thin and threadlike substance that forms ‘webs’ in the soil – it’s the vegetative part of a fungi, from which the mushroom fruits. The fungal threads wrap around the root tips of plants (including trees), and there is an exchange of nutrients. This is a classic symbiotic relationship where both parties benefit from co-operating and on the surface, it doesn’t seem that interesting. But this is more than simple symbiosis. The same threads form connections across forests, sometimes between hundreds of organisms.
These connections are like an underground internet. Biologists refer to these networks as the “Wood Wide Web.” Trees do not just exchange nutrients with the fungus – they use the network to transfer nutrients to other trees of their species. This is interesting enough by itself, but it turns out that they will prioritise their offspring. This makes perfect evolutionary sense – what better way to ensure that genetics survive? Still, I don’t often think of oak’s as doting mothers, but the evidence shows that they actively nourish their young.
The web is not only used to transfer nutrients. It is also used as a means of communication. Electrical impulses are sent along the network to warn other trees of, for example, insect infestations. Trees can then defend themselves by pumping organic pesticide into their leaves. If a tree in the network comes under attack, a signal is sent to other members of the species as a warning. Studies have shown that the signal is received, as a message of sorts, and that the receiver will pump the same pesticide out in anticipation of the oncoming assault.
In some cases, these signals are not restricted to members of the same species, and other plants have shown a kind of ‘eavesdropping’ behaviour. They listen in to the network to catch wind of any circulating rumours, to the extent that a plant can.
Some plants even possess a memory of sorts. A mimosa – a type of tropical herb, is a ‘sensitive plant’. They close their leaves to protect themselves from damage. An experiment was done where drops of water were pipetted onto the mimosa at regular intervals. At first the mimosa would recoil. After a while they stopped reacting, as if they had learnt that they were in no danger from the water. If the experiment was repeated weeks later, they “remembered” that they were safe and didn’t flinch.
So next time you’re in the woods, take a second to appreciate the full extent of our ignorance. Even something as familiar as a tree hides mystery that we’re only just beginning to unravel. With our current understanding we cannot say what it feels like to be a tree, or if a tree has something we can call experience. Complex behaviour does not imply awareness. Still, we know it’s not as simple as we once thought. And that’s why science is a lot of fun.
I was first exposed to mycelium networks through an amazing book called The Hidden of Trees by Peter Wohlleben. If you’ve found this article interesting, check it out for a more detailed exploration of the nuanced and complex lives of our leafy companions.