Are plants smart?

As a plant person, you already know that plants have sensitivities, many beyond our understanding. But are plants smart?

You feel guilty when you forget to water. You praise them when they do well. You know that they respond to your voice because you talk to them and you also know that they respond to music.

You know that being among them removes stress and helps people heal physically. Health practitioners are recognizing this and building gardens at hospitals and long term care facilities.

Now science is catching up and learning just how some of these things work.

The case for personification

Comparing animals and plants to humans by attributing like qualities to them was not that long ago viewed with disdain. It was definitely a literary no-no. Now, it is hard to be quite so sure.

Plants and animals, of both the so-called higher and lower orders, have just too much in common to ignore. Plant “senses” include the use of chemicals, gravity, moisture, light, oxygen, temperature, infection, carbon dioxide, parasites, electricity and touch. They also have a sense of balance. Humans use many of the same tools to get through life and continue the species.

We see plants as static, earth-bound things that are captive to their environment, but plants have busy lives. They signal within themselves and among themselves. They are busy communicating and competing just as we are. They calculate cost versus benefit and, after analyzing the result, they take controlled actions to mitigate stress or to capitalize on advantages. They can recognize a negative from a positive and learn from experience using these memories to modify behaviour. They are also intensely territorial, creating allies and enemies.

Plants are also sensitive to time. We pretty much understand now that plants have photosensitive hormones, a molecular clock that reacts to different wavelengths of light. This is one of the ways they know when to bloom or when to drop leaves and so on. Plants can tell if it’s day or night, how long the day is, how much light is available, where the light is coming from.

Smart plant “brains”

Humans consider animals, especially mammals like themselves, to be a superior life form because we have brains based on neuronal networks that allow us to think and react consciously. (Ironically, the Greek word neuron means “vegetable fibre”.)

Plants have a similar capacity, but their reactions travel along what we now call “signaling pathways”, which provide the basis for learning and memory. Like us, they have the capacity to react both fast and slow. Slow reactions are usually chemically based. Faster ones are electrically based or transmitted through a system of volatile signals such as lipid based hormone signals.

Auxins are well known for their place in plant growth but another of these hormones is jasmonate, isolated from the jasmine plant. Methyl jasmonate (MeJA), metabolized from jasmonate, are the molecules in the signaling pathways that are responsible for such things inter-plant communication. For example, a wounded tomato plant sends chemicals to an insect-attacked leaf that will inhibit the insect’s ability to digest food. MeJA on leaves can be quickly transmitted through the air to warn other plants of a threat. When the airborne chemical is detected, other related plants will begin to produce chemical defenses.

Lop off a limb to save the tree

Many plants have the ability, thanks to jasmonates, to induce death (plant suicide) in a specific part of a leaf that is attacked by a pathogen or an insect in order to save the rest of the plant. You will see this as a leaf that is dead on one side while the rest of the leaf and plant looks fine. What is even more interesting is that once this happens, the plant has the ability to recognize the pathogen and become resistant and even immune to further attack.

Think how handy this would be in animal life.

Plants may also have goals, although they may not be as conscious or directed as ours (although who knows) but they do have intentions. Think of the way the tendrils of a vine “find” their way to support. Think of how those tendrils ever so gently caress their way on to the support, then harden and cling with an iron-like tenacity that can sustain many times their weight.

What makes plants so smart?

Plants employ the same tools that make mammals and other animals “smart”: chemistry, electricity, physics, a relationship with the sun and its relationship with the earth.

It just makes sense. “All life must work within the physical laws of matter”, says a Wikipedia author.

And, we might add, any other laws we don’t yet understand.