" So, let's get back to why the roots are the most important part of a tree. Conceivably, this is where the tree equivalent of a brain is located. Brain? you ask. Isn't that a bit farfetched? Possibly, but now we know that trees can learn. This means they must store experiences somewhere, and therefore, there must be some kind of a storage mechanism inside the organism. Just where it is, no one knows, but the roots are the part of the tree best suited to the task. The old spruce in Sweden also shows that what grows underground is the most permanent part of the tree-and where else would it store important information over a long period of time? Moreover, current research shows that a tree's delicate root networks is full of surprises.

It is now an accepted fact that the root network is in charge of all chemical activity in the tree. And there's nothing earth shattering about that. Many of our internal processes are also regulated by chemical messengers. Roots absorb substances and bring them into the tree. In the other direction, they deliver the products of photosynthesis to the tree's fungal partners and even route warning signals to neighboring trees. But a brain? For there to be something we would recognize as a brain, neurological processes must be involved, and for these, in addition to chemical messages, you need electrical impulses. And these are precisely what we can measure in the tree, and we've been able to do so since as far back as the nineteenth century. For some years now, a heated controversy has flared up among scientists. Can plants think? Are they intelligent? "

― Peter Wohlleben , The Hidden Life of Trees: What They Feel, How They Communicate: Discoveries from a Secret World