We tend to think of plants as passive organisms, the backdrop for looking at more interesting animals roaming around in the foreground. But the world of plants is by no means docile, it is simply working on a separate time scale and in a different medium, and we’re only just starting to decipher it.
From towering redwood trees to cave-dwelling nettles, we have been misunderstanding the very organisms that allow us to exist. They move, wage war, count, talk to each other, learn from past experiences, and might even go to sleep.
Whether or not this constitutes intelligence or as some even suggest, consciousness, is fiercely debated, but what is true is that there is a hell of a lot going on around us that we have been blind to.
One of the most striking discoveries in recent times has been that of the mycorrhizal – or fungal – network, inter-wound with the roots of most plants, be they trees or shrubs. When it was discovered, it was thought that these fungi were just in cahoots with the plants, providing them with water and other nutrients in the soil in exchange for carbohydrates and energy derived from photosynthesis.
It wasn’t long before scientists realized that these fungal filaments, however, were not just found between the roots of single plants, but stretched between individuals too. It turns out that they can use the fungi to send nutrients to neighbors who might be struggling. Incredibly they are not even limited to connecting and helping the same species of plant.
But research suggests that the fungal network snaking through the soil is not only used to provide nutrients to other plants: it might also allow communication.
Experiments have shown that if one plant is being attacked by a disease or pest, it will send information through the mycorrhizal network to its neighbors. This gives the other plants a valuable period of time in which they can pre-emptively mount their defense. Studies have found that after being warned in such a way, these plants are then less likely to get infected, and if they do, show fewer signs of damage. The fact that plants can in effect talk through this network has people calling it the "wood wide web".
But as with any network connecting individuals, while most plants contribute to the community, there are those that exploit it. Some – such as a myriad of orchids – will tap into to the fungi and take nutrients without paying any in, parasitizing the trees around them. But others are far craftier.
If nutrients and water can pass along the mycorrhizal network, then so can other molecules. And experiments have shown how some plants do seem to exploit the fungi to wage chemical warfare with their competitors. Known as “allelopathy,” scientists were already aware that plants release these molecules in general, but one study using golden marigolds showed that the flowers do seemingly use the fungal networks to transport their toxins away from the main plant and suppress rivals farther away.
It also seems that plants might remember. Yep, you read that right.
Experiments on a plant known commonly as “the sensitive plant”, because when its leaves are touched they recoil and fold up, suggest that it might – somehow – form memories. One paper found that after dropping the plant once, causing its leaves to fold, the plant then failed to move when it was subsequently dropped as if it had learned that this was not a threat.
What is more, even after a break of one month, the plant still refused to curl up when it was once again dropped. Whether or not the plant has actually formed memories, and if so how they manage it, is still a mystery.
Even weirder – and this is something else we don’t understand – is that we seem to be able to put plants to sleep. Researchers tested a variety of different plants, from peas to Venus flytraps, and found that after dosing them with anesthetics normally used in humans, the plants became unresponsive. The pea shoots stopped moving, the flytraps stopped trapping, and to all intents and purposes, the plants were apparently asleep.
After about an hour or so in this condition, the groggy greenery seemed to wake from their slumber, and start functioning again. This is not as farfetched as it sounds. After all, plants make plenty of chemicals that affect us, so why would ones we make not affect them? But does raise some really weird questions.
How is the anesthetics affecting the plants? Are the plants really asleep? And if they are, does that mean that when they wake, they’re regaining consciousness?
What is clear, however, is that plants are far more than just mere biological robots, responding to their environment and stimuli in kind. They are not merely a backdrop to everything else, they have their own entire parallel world, one which we have only scratched the surface of.