Plants don’t see like we do. They don’t experience smell, taste, or touch like our human senses either. In fact, without brains, they can’t truly be said to “experience” anything at all. Contrary to popular belief, there’s no body of reliable evidence that plants respond to certain kinds of music, or grow better if you sweet talk them (school science fair projects notwithstanding). There’s no conclusive evidence that plants can “hear”, though they can react to certain kinds of vibrations. In spite of books like 1973’s The Secret Life Of Plants by Peter Tompkins and Christopher Bird (roundly scorned by plant researchers) plants don’t think, have feelings, or experience pain in any sense comparable to ways humans do (And telepathy? Don’t even go there!)
Nevertheless, plants are amazing in the things they can do. Even where their abilities seem to mirror those of humans, they’ve evolved brilliant alternative ways to perform such functions.
The book What a Plant Knows: A Field Guide to the Senses by Daniel Chamovitz is an enjoyable collection of comparisons between plant ways and human ways of sensing things. Because, as different as they are, plants do have methods of encountering and evaluating the environment around them. They have to, in order to survive and thrive.
Even though they don’t exactly “see”, they do sense light, of course, especially to optimize the efficiency of the photosynthesis that sustains them. We all know about plants growing toward the sun. Photoreceptors in the tips of plant shoots signal cells lower down to grow in such a way as to make the stem bend toward the source of light. Using chemical dyes that absorb various frequencies of light, they can distinguish colours too. Blue light helps regulate plants’ daily cycles—circadian rhythms just like humans have (which means, yes, they can even get jet lag). Plants rely on certain shades of red light, like those of sunrise and late sunset, to tell them when the day begins and ends. That enables them to distinguish the shorter days of autumn from the lengthening days of spring, which is important information for picking their optimal time to bloom, produce fruit, or drop their leaves. Because of this, greenhouse growers can turn lights on for a few minutes in the middle of the night to trick some flowers into blooming out of season—just in time for Mothers Day, for instance.
Plants can tell when they’ve been touched (and may respond as if threatened, so don’t pet your petunias). After all, they need to know if there are any obstacles, or unwanted sources of shade springing up beside them. And some explore nearby objects as a means to climb higher into the sunlight and air. Though there’s no reason to believe they experience pain, they certainly “know” when parts of them have been damaged and react appropriately. Which brings us to some of the incredible ways plants use odours.
Sure, they give off pleasant perfumes to attract bees and other pollinators, but they also use scents to tell their fruits to ripen at the same time, or their leaves to close up and fall off for winter. When attacked by insects, some plants can use aromatic chemicals to attract other insects that prey on the attackers. What’s more, they can detect such signals from other plants. Thus alerted that a neighbouring plant is being munched on by pests, they might make their own leaves unpalatable or even poisonous to the predators.
The range of these capabilities is almost as varied as the many thousands of species around the world, and while some of the processes involved are similar to human biology (after all, we share a common ancestor in the wiggly things of the primordial Earth’s waters), others are wonderfully different.
We humans have come to rely overwhelmingly on mechanical and electrical technology, sometimes inspired by other animals and birds, but plant solutions offer enormous potential. Some fledgling efforts in this area include Plant-e (generating small amounts of electricity from plants) and Botanicus Interactus (a technology that relies on the electrical conductivity of plants for some diverting applications mainly related to touching them). But a little imagination could produce all kinds of possibilities. Plant-based weather stations. Geological surveying. Earthquake early-warning systems. Distribution of medicines (picture vaccine-type remedies or other disease cures spread on the air like pollen).
I applaud SF writers who’ve described alien races that grow their spaceships and buildings instead of manufacturing them. Why not? They’d be reliable, adaptable, and self-repairing. Not to mention bonus features like solar power and oxygen regeneration. Why not use mycelial networks in the soil for our own communications, as plants already do? Have cities with water and sewage facilities based on the cellular water transport systems of trees? And since plants can’t run away from threats, their methods of defense should be a natural inspiration for designing colonies and outposts as we reach out into the great unknowns of outer space. Many plants evolved to be eaten, so they can sustain substantial damage thanks to elaborately decentralized functionality and redundancy. Being eaten isn’t a pleasant image when we think of future contact with alien beings (!), but surely the redundancy and resiliency of plants offers a lesson for any endeavour under hazardous conditions.
Let’s start looking to plants for inspiration and not just vitamins. And although it’s nearly certain that plants don’t have anything comparable to the consciousness and awareness that we prize so much, who knows what a few million more years of evolution might produce? It did quite a lot for some scrawny lowland apes.