Plants are an essential part of our existence. They are the source of everything we rely on to survive. From our food, air, and water, to our climate, clothes, and life-saving medicines. Although plants play such a key role in our lives, they are often taken for granted as something that exists to serve us and which we have little in common with. However, are plants more human than we think?
In times of high stress, it isn’t uncommon for people to scream out in frustration or let out a cry for help. This can often feel good and lets others know how we are feeling. However, this emotional response isn’t only done by humans. In fact, Tel Aviv University scientists have shown that plants have this same response when put under drought or physical stress. When placing microphones near stressed tomato and tobacco plants their screams were detected from just 10 centimetres away. Due to the ultrasonic range of these screams (20 to 100 kilohertz) they are undetected by human ears; however, other organisms can likely detect these invisible screams from up to several meters away, which may allow for animals and other plants to react.
In addition to this, plants were found to produce distinct rates of sound depending on the stress type inflicted. On average per hour, screams produced by drought-stressed tomato plants were around 35, while tomato plants under physical stress released around 25. Drought-stressed tobacco plants produced around 11, while cut tobacco plants made around 15. Screams produced by untouched plants, in comparison, fell below one. The difference in noise between stresses was so distinct that the team were able to place the plants into the correct category of ‘dry, cut or intact’.
So, not only do plants scream out in pain just as we do, but they also have the capability to distinguish stress types and vary their reactions accordingly, much like our varied reaction to extreme thirst versus a painful cut. This is incredibly exciting research for farmers as this technology could be used to detect when plants in their field may be undergoing stresses such as drought.
While it’s not yet clear whether other plants respond to these screams, one plant type known for its very efficient communication is trees. A forester named Peter Wohlleben claims that trees communicate via a below-ground ‘woodwide web’ in which electrical signals are sent (similar to our nerve system). This can be used to communicate distress to nearby trees when under attack, as well as for nurturing seedlings (much like we nurture our children), feeding afflicted trees, and restricting others in order to keep the community strong. According to Wohlleben, Beech and Oak trees can form forests that last for thousands of years because they act like families and mercilessly protect their own kind.
These claims are supported by Suzanne Simard, a forester from the University of British Columbia. Her research shows information is passed in the form of nutrients, chemicals, defence signals, hormones, and water via the Mycorrhiza fungi colonising the tree roots, forming a symbiotic relationship. In a single forest, a mother tree can be connected to hundreds of other trees and sends her excess carbon via this fungal network to the understory seedlings. Unbelievably, they can recognise their trees of kin and colonise these with a bigger fungal network, allowing them to provide more carbon. These mother trees also choose to reduce their own root competition, selflessly giving more room for their children’s roots to grow. In addition, when injured or dying, they’ll send messages of wisdom onto the next seedling generation. Carbon and defence signals are sent via the fungal network, increasing their seedling’s resistance to future stresses. There is no other love for a child like a mother tree for its seedling.
So, plants can communicate to other plants, but what about plant-to-human communication? Recent technology is contributing to one plant’s humanistic skill set. It appears spinach can now email important information to scientists, such as the presence of explosives or dangerous chemicals in the soil. Astonishingly, nanotechnology engineers have discovered a way to input electronic sensors onto the plants leaves, allowing their roots to register any contact with certain chemicals, such as nitroaromatics, a chemical often found in explosives. If detected, the plant sends a signal detected by infrared cameras which immediately sends an email to alert scientists.
Professor Michael Strano who led the study believes that this new technology, known as ‘plant nanobionics’ could also be used to detect pollution or environmental changes in order to help stop climate change. In addition, another study from American University has found that spinach could be used as an energy-efficient alternative to the current lithium-ion batteries often used in electronics. For such a modest salad plant, spinach appears to be doing an awful lot to help save this planet.
So, perhaps plants are more human than we know. They cry out when under stress, build communities, sacrifice themselves for their children and loved ones, pass valuable information, and even use email to save the planet. There is so much more to learn about the abilities plants possess. It is likely more similarities between humans and plants will surface as we continue to discover more about their capabilities. Through combining forces, we may find new ways to help with urgent climate and environmental issues that could one day save the world.