Revealed: sunflowers are social creatures

Rooting for you: The Guinness World Record for the tallest sunflower is 8.23 m — about the size of a house.

Should plants have rights? Scientists increasingly think of plants as intelligent creatures. New studies show they can tell each other apart, and use 20 senses to understand their environment.

We often think of the natural world as brutally competitive. Survival of the fittest is its only law. Weeds strangle flowers. Plants fight for space, sunlight and nutrients.

But research published yesterday radically challenges that understanding.

The study found that sunflowers — far from competing with each other — work together to share nutrients, even if it requires self-sacrifice.

Helianthus annuus, the most common species of sunflower, has one main root embedded in the earth. From there, it sends out smaller, winding roots into the surrounding soil. A sunflower in very rich earth could send out hundreds of these tiny roots to hunt for nutrients.

That is unless they are sharing the soil with a neighbouring sunflower. In that case, they will restrict the growth of their roots — almost as if the flowers had made a deal not to compete with one other.

Researchers say the findings show that plants are aware of their “social environment”.

“We need to recognise that plants not only sense whether it’s light or dark, or if they’ve been touched, but also [what] they are interacting with,” Susan Dudley, a plant evolutionary ecologist.

It is just the latest in an avalanche of discoveries that are revolutionising our understanding of plant intelligence.

Like humans and other animals, plants look out for their own. Scientists in China found that rice plants grew faster and stronger when they were growing alongside their close relatives.

Meanwhile, Arabidopsis plants growing next to close family move their leaves to avoid placing them in the shade. If, on the other hand, the neighbouring plants are not of their kin, they are happy to leave them in the shade.

But trees have the most complex behaviour of all. Scientists have uncovered a huge underground web of fungi and bacteria that trees across the world use to talk to each other. Nicknamed the “wood wide web”, this social network allows trees to share nutrients; wage war against each other, and pass chemical warnings when they are under attack.

In the UK, cruelty to animals is punishable by up to five years in prison. Should similar punishments apply to cutting down a tree, or picking flowers?

Keep off the grass

Of course, say plant neurobiologists like Stefano Mancuso. According to him, our traditional understanding of intelligence (basically, that it requires a brain) is all wrong. Plants have at least 20 senses to monitor their environment. They hunt and solve problems. They can interact and tell each other apart. They are as sentient as many animals. We need to respect them.

But others are less convinced. “If we stretch the meaning of terms like ‘consciousness’ and ‘intelligence’,” writes Ellie Moldano, “we can even apply them to one-celled organisms but, in doing so, I think this renders them far less meaningful. There’s a world of difference between the biochemical reaction of plants and the experience of living beings who can think and feel.”

You Decide

  1. Should plants have rights?
  2. Are humans the most important species on the planet?

Activities

  1. Write your own definition of “consciousness”. Compare and discuss your answers as a class.
  2. After carrying out your own research, draw a diagram explaining how the “wood wide web” works.

Some People Say...

“He that plants trees, loves others besides himself.”

Thomas Fuller (1608-1661), English churchman and historian

What do you think?

Q & A

What do we know?
New research published yesterday has revealed that sunflowers can cooperate to share nutrients with each other. It is not the only example of intelligent plant behaviour. When a giraffe eats an acacia, for example, the tree begins to pump out ethylene gas. When the surrounding trees pick this up, they transfer unpleasant-tasting tannins into their leaves.
What do we not know?
What it really means to say that plants are “intelligent”. For centuries, western philosophy and science have viewed animals and plants as machines whose function is to survive. Charles Darwin was one of the first to discuss plants as sentient beings. After meticulously studying plants, he said their main root “acts like the brain of one of the lower animals”.

Word Watch

Survival of the fittest
A phrase that came from Charles Darwin’s evolutionary theory. It means that the organisms that are most adapted to their environment will survive to pass on their genes, while the ill-adapted will die out.
Published
In Proceedings of the Royal Society B.
Helianthus
From the Greek words “helios” for sun and “anthos” for flower.
Nutrients
A substance that provides the nourishment living things need to survive.
Arabidopsis
Also known as rock cress, a small flowering plant.
Kin
Family.
Sentient
Able to perceive and feel things.

PDF Download

Please click on "Print view" at the top of the page to see a print friendly version of the article.