Charles Darwin, aside from evolution, came up with the “root-brain” hypothesis along with his son Francis, in their book The Power of Movement of Plants. This suggests the roots act like a brain network. Ignored at the time (evolution was enough to deal with without the suggestion of trees having brains as well) it is only now beginning to be taken seriously.
I have been sitting drawing beech tree roots today. They are fascinating indeed. Largely unseen they undertake a big proportion of a trees practices and are often the same size as the tree above ground. Their skin can have an interesting textured quality and they curl around each other like snakes which is very good to draw. Where I live in London you can see the roots bursting through the Tarmac, looking distinctly like monsters from the underworld. What happens in roots and around roots is just as strange as what they look like.
Roots search the soil for water and minerals that they absorb and then send up to the leaves for photosynthesis. A root grows from its tip which it pushes forward through the soil. The root tip can detect the pull of gravity and aims itself downwards into the soil. Behind the root tip are root hairs that grow into the soil to gather supplies.
Fungi have symbiotic relationships with roots, this is called Mycorhizass. There are two main kinds of mycorrhiza, ones that penetrate the roots and ones that surround the roots without penetrating. The fungi transfer essential minerals such as nitrogen and phosphorous from decaying matter to the tree. The fungi cannot photosynthesis so the tree does this for them, providing the fungi with energy.
Other advantages to such relationships include speeding plant growth, stimulating fine root development and lengthening the life of the roots. They can also protect plants from drought, predators (such as nematode worms), and micro-organisms that cause disease. In areas polluted by toxic heavy metal it seems fungi can buffer their tree partners against harm. A diversity of fungi is valuable to a tree, as different fungi will specialise in the various functions, so one species may be good at taking up particular nutrients, while another will be better at producing enzymes.
Trees have also been found to pass on carbon dioxide to other trees in need of it, even trees of different species, through the roots. This is also thanks to a symbiotic fungi in the soil. In fact new discoveries about roots really put them as essential and quite incredible things. I’m reading a lot about tree communication at the moment, I’ll write about it more once I’ve got my head round it. The idea of them having a “root brain” where the tips of the root are small neutron centres seems to fit in somehow.