Do plants have senses?
Most people would say no, but in fact they do. Their senses are not like ours, but plants have been on earth much longer, and have evolved in complex ways to perceive and adapt to the environment. They can not move to escape from danger so they learned to perceive small changes around them to adapt and defend themselves.
They can not see, but they are able to perceive light. Not just visible light, but also wavelengths for which we are blind like ultraviolet and infrared. If other plant shades them, they will grow faster to look for light. Many plants regulate their life cycle depending on the season. To decide the most appropriate time to bloom some measure the duration of the night while others count the hours of coldness (some do both). They haven’t got ears but are able to perceive vibrations. They also sense magnetic fields, gravity, chemical gradients, humidity … and respond to these stimuli.
Plants are social beasts (no, we haven’t gone crazy). Plants do communicate among them. Of course they don’t talk or whatsapp each other but use chemical signals. When one plant is attacked by a pest it releases characteristic chemical molecules into the air. These substances are perceived at great distances by other plants which begin to prepare their defenses before the pest arrives. Currently there is a lot of research in this area: plants can sense some chemicals called elicitors and prepare before the attack happens, like if they were vaccinated. Researchers are now trying to understand this chemical language.
How can plants defend themselves?
They can manufacture a lot of chemicals: antioxidants, salicylic acid, poisons, indigestible molecules… Even more amazing, they are able to manipulate animals to come to their aid. It is now known when some plants are attacked, they synthesize and release certain molecules that attract insects which are predators to the pest. It’ seems like they are calling the police to arrest the criminals hurting them. They also produce chemical molecules whose single purpose seems to be to manipulate the brains of animals: the vast majority of natural drugs come from plants (caffeine, nicotine, opiates, THC …)
If plants had a brain this would definitely be the root. Roots receive signals from all surrounding stimuli and decide what molecules need to be synthesized and where to send them. As we don’t normally see them we tend to forget they exist, but healthy roots are essential for the health of the whole plant.
Plants also communicate through the roots, using fungi as a medium. These beneficial fungi called arbuscular mycorrhizas live in natural soils and, like a science fiction alien, enter into the plant root cells producing live structures that belong both to the plant and to the fungus. They help to trade water, nutrients and information (alarms) among different individuals.
Science’s advances in the understanding of the complex relationships of plants amazes us for their adaptability and ingenuity to manipulate their surrounding medium. We are today more aware of how little we know about these living things that colonized earth 450 million years ago and changed our planet enabling life as we know it.