Radical thinking

I imagine most people who've ever stuck a few pussy willow twigs into a jar of water will have noticed when they come to throw them out that little roots have emerged all ready to start growing if placed in damp soil. If you look closely you can see that each of these little suckers (radicles) is covered with tiny sensory filaments.These are able to detect the presence of around 15 different chemicals as well as to monitor temperature, gravity, light, soil structure and other features of their environment.
As long ago as 1880 Charles Darwin wrote in one of his last books, The Power of Movement of Plants,  that the tip of the radicle acts like the brain of lower organisms and he illustrated his theory with some experiments he had done. But his 'root-brain' theory was castigated by botanists at the time and fell into disfavour.
In recent years however a group of plant scientists have taken up his idea and have developed it with further evidence about plant "intelligence". That's not to say that plants have conscious intention in what they do but there's no doubt that they respond to stimuli, move,  alter their chemical composition, sleep and even communicate with each other. For example, some plants when attacked by predators (caterpillars, deer) appear to be able to signal the fact to others nearby which will as a result increase the amount of toxicity in their leaves to act as a deterrent. And in a woodland situation it's been shown that mature trees will share nutrients with younger trees of the same species to support them in times of stress. Different species may even exchange resources in a tit-for-tat fashion.
The scientists who are engaged in this field (neurobiology, a controversial term in itself) suggest that roots systems are sentient but operate not centrally like brains but like swarms - of bees, ants or starlings for example - that move and react as a mass. A root network can also be compared to the internet with its multitude of interconnections and could be used as a paradigm for building new electronic systems of communication.  Both have the capacity to continue functioning when the greater part is destroyed.

I find this absolutely fascinating but I realise that not everybody does. There's a great  little TED presentation by one of the leading plant intelligence proponents Stefano Mancuso here, (worth watching for his passion and his wonderful Italian accent alone.)  Much longer and more detailed is this absorbing article, probably only for the seriously interested with time to spare.