The distributed 'intelligence' of fungi

Ashutosh Jogalekar, Life. Distributed. 3 Quarks Daily, August 31, 2020:

...perhaps the most interesting quality of fungi lies not in what we can see but what we can’t. Mushrooms may grace dinner plates in restaurants and homes around the world, but they are merely the fruiting bodies of fungi. They may be visible as clear vials of life-saving drugs in hospitals. But as Sheldrake describes in loving detail, the most important parts of the fungi are hidden below the ground. These are the vast networks of the fungal mycelium – the sheer, gossamer, thread-like structure snaking its way through forests and hills, sometimes spreading over hundreds of square miles, occasionally being as old as the neolithic revolution, all out of sight of most human beings and visible only to the one entity with which it has forged an unbreakable, intimate alliance – trees. Dig a little deep into a tree root and put it under a microscope and your will find wisps of what seem like even smaller roots, except that these roots penetrate into the trees roots. The wisps are fungal mycelium. They are everywhere; around roots, under them, over them and inside them. At first glance the the ability of fungal networks to penetrate inside tree roots might evoke pain and invoke images of an unholy literal physical union of two species. It’s certainly a physical union, but it may be one of the holiest meetings of species in biology. In fact it might well be impossible to find a tree whose roots have no interaction with fungal mycelium. The vast network of fibers the mycelium forms is called a mycorrhizal network.

The mycorrhizal networks that wind their way in and out of tree roots are likely as old as trees themselves. The alliance almost certainly exists because of a simple matter of biochemistry. When plants first colonized land they possessed the miraculous ability of photosynthesis that completely changed the history of life on this planet. But unlike carbon which they can literally manufacture out of sunlight and thin air, they still have to find essential nutrients for life, metals like magnesium and other life-giving elements like phosphorus and nitrogen. Because of an intrinsic lack of mobility, plants and trees had to find someone who could bring them these essential elements. The answer was fungi. Fungal networks stretching across miles ensured that they could shuttle nutrients back and forth between trees. In return the fungi could consume the precious carbon that the tree sank into its body – as much as twenty tons during a large tree’s lifetime. It was the classic example of symbiosis, a term coined by the German botanist Albert Frank, who also coined the term mycorrhiza.

However, the discovery that fungal networks could supply trees with essential nutrients in a symbiotic exchange was only the beginning of the surprises they held. Sheldrake talks in particular about the work of the mycologists Lynne Body and Suzanne Simard who have found qualities in the mycorrhizal networks of trees that can only be described as deliberate intelligence. Here are a few examples: fungi seem to “buy low, sell high”, providing trees with important elements when they have fallen on hard times and liberally borrowing from them when they are doing well. Mycorrhizal networks also show electrical activity and can discharge a small burst of electrochemical potential when prodded. They can entrap nematodes in a kind of death grip and extract their nutrients; they can do the same with ants. Perhaps most fascinatingly, fungal mycelia display “intelligence at a distance”; one part of a huge fungal network seems to know what the other is doing. The most striking experiment that demonstrates this shows oyster mushroom mycelium growing on a piece of wood and spreading in all directions. When another piece of wood is kept at a distance, within a few days the fungal fibers spread and latch on to that piece. This is perhaps unsurprising. What is surprising is that once the fungus discovers this new food source, it almost instantly pares down growth in all other parts of its network and concentrates it in the direction of the new piece of wood. Even more interestingly, scientists have found that the hyphae or tips of fungi can act not only as sensors but as primitive Boolean logic gates, opening and closing to allow only certain branches of the network to communicate with each other. There are even attempts to use fungi as primitive computers.