The Roots of Plant Intelligence

We have become used to the idea that intelligence is distributed more widely through the animal kingdom than we used to think. Now it's the turn of the plants. I recently watched a TED lecture that blew me away, as many of them do. Here's the summary of the lecture from the TED site:

Plants behave in some oddly intelligent ways: fighting predators, maximizing food opportunities ... But can we think of them as actually having a form of intelligence of their own? Italian botanist Stefano Mancuso presents intriguing evidence.

Professor Mancuso, a founder of the science of plant neurobiology, begins his talk by showing how our culture for eons has underestimated plants. For example, in the Bible story of Noah's Ark, the animals went on two by two - but there are no plants! And when David Attenborough says, in his wonderful breathy awestruck way, "Blue whales - the largest creatures on the planet" - he's forgetting the Sequoiadendron giganteum!

Yet plants show many of the characteristics we associate with animals. They move and sense and respond in sophisticated ways. They sleep. They can can negotiate mazes, and plan for the future ("the ground-hugging mayapple plans its growth two years into the future, based on computations of weather patterns." - Christian Science Monitor, New research opens a window on the minds of plants.)

How can they do it all - without a brain? Mancuso suggests that plants do have a brain. It's in the tips of their roots, and it's networked. He quotes the last paragraph in Charles Darwin's book The power of Movement in Plants":

It's hardly an exaggeration to say that the tip of the radicle thus endowed, and having the power of directing the movements of the adjoining parts, acts like the brain of one of the lower animals.

Mancuso shows a time lapse movie of a root growing against a slope. I put a still of that section at the top of this post. The root behaves just like a worm, feeling its way.

The key is in the region of the root apex called the "transition zone" less than 1 mm in length. It consumes the most oxygen, and electrical signals from this zone look a lot like the signals neurons make. And here's the thing - there are only a few hundred cells in one root apex, but how many roots are there in a single plant of rye? - I reproduce his slide and the statistics from the following one:

One Rye plant has---
Total number of roots: 13,815,672
Number of root apexes: 11,483,271
Total length: 622 Km
Surface area: 237 sq. m

That's a lot of surface area of nerve type tissue. Mancuso compares root structures to the internet, and suggests they work in the same way: You can remove 90% of the root apparatus - or the internet - and it still works.

Mancuso studies technology as well as plants. Why do we base robots on people - androids. Why not plantoids. For example, if you want to explore soils or colonize new territory, be inspired by plants, who are the masters of these types of activities. He also studies plant-machine hybrids - the machines can connect with the plant using the plant's own electrical signals

With a bit of luck I've embedded the video:



Otherwise, here's a link.

Here are a few more snippets I found - your browsing will not doubt find other great articles:

Numerous studies on rhizomes suggest that higher plants must be able to construct a three‐dimensional perspective of their local space and optimize their growth patterns to exploit resources, thus receiving rewards for successful behaviour. To any wild plant the environment represents a continual maze that must be successfully navigated.

From Annals of Botany, Aspects of Plant Intelligence by Anthony Trewavas
http://aob.oxfordjournals.org/content/92/1/1.full

To wrap up this fascinating topic - I found this on the home page of The Society for Plant Neurobiology: (I added the bolding for ease of skimming.)

For a better understanding of the world around us, it is important that we develop and share the growing understanding of plants as dynamic and highly sensitive organisms. No longer can plants be viewed and portrayed as passive entities merely subject to environmental forces, as 'automata'-like organisms based only on reflexes and optimised solely for accumulation of photosynthate. With a fuller understanding of signaling and communication within and among plants, it becomes clear that these sensitive biological organisms actively and competitively forage for limited resources, both above and below ground. In addition, plants accurately compute their circumstances, use sophisticated cost benefit analysis, and they take tightly controlled actions to mitigate and control diverse environmental stressors. Plants also emerge as capable of discriminating positive and negative experiences, and 'learning' from their past experiences. Plants use this cognitively acquired information to update their behavior in order to survive present and future challenges of their environment. Moreover, plants are also capable of refined recognition of self and non-self, and are territorial in behavior.

That's the science - but as I wander out in the garden, I'm back with the poetry and mysticism of it all - Wordsworth, Emerson, and Whitman are with me, and I sing the body electric.