Plants Talk, And It’s Not Just Danger Warnings
In their supposed idleness, plants have almost always been neglected when it came to research. Plants fulfil their purpose of serving as nutrition, and perhaps, as a pleasant decor for the house. What else could they possibly be capable of?
In this deemed idleness, however, plants strived to live, communicating in a language unknown to humans. They have been talking since their first time on Earth. It started, perhaps, with warning signs to keep neighbors on alert for predators. These signs are volatiles that is released from neighbors who have been attacked or are under attack (1). The effect of this volatiles, as found by Heil et al. in a research study on Sitka willow trees, was increased resistance in undamaged neighbors and increased levels of phenolics* in undamaged poplar and sugar maple trees sharing the same air with that of those that were attacked. The resistance is generally in the form of the secretion of insect-repelling chemicals. An implication of this is that idleness was not the case. The, so called, ‘brainless creatures’ were capable enough, after all, of communicating and interpreting messages to both members of their species as well as outsiders.
Nonetheless, all research published until recent times came to a halt when they were deemed too artificial or irrelevant. Richard Karban, an ecologist at the University of California, Davis, was one of the few to overcome the obstacle of criticism. Through controlled experiments with sagebrushes, he was able to confirm that plants that are under attack release airborne chemicals, and plants that do not receive them to up-regulate their defence mechanism (2).
Following that, Greg Gage has claimed that plants do not act entirely indecipherable or unknown behavior as we may have previously thought them to be. Just as our neurons use electrical signals to move our muscles, plants have the ability to communicate using electricity, both within themselves and with others (2). During a TED Talk, Gage stated that the release of an action potential** is responsible for the Venus flytrap’s ability to trap a fly and the Mimosa’s leaves to close once touched. Along with being another indication of the complexity of plants, this also shows that there are multiple ways that a plant can get its point across.
Gage’s demonstration consisted of an ‘interspecies plant-to-plant communicator’, which is essentially a Venus flytrap connected with a mimosa. When the mouth of the Venus flytrap is stimulated, the action potential is recorded and sent to the mimosa, which induces the behavior of the mimosa closing its leaves. This is therefore a simple demonstration of plant communication through electric signals.
Besides the two languages, airborne chemicals and electric signals, plants can also use the soil as a medium of communication. Research by Velemir Ninkovic, an ecologist at the Swedish University of Agricultural Sciences, has shown that this communication generally carries the aim of survival (4). Sometimes, a plant is an obstacle between its neighbor and growth. A human could easily fight with their neighbor or move out of their house if their neighbor posed a threat. Unfortunately, plants don’t have the same ability. However, this doesn’t leave them more vulnerable. A plant can secrete chemicals into the soil through its roots and cause its neighbor to grow more aggressively and out of their way. As Ninkovic puts it, “they use signals to avoid competing situations and to prepare for future competition.”
Ninkovic and his team have demonstrated this in a study where they simulated a stressful environment by brushing the leaves of a plant for a minute every day. This was to model the touch of a nearby plant, and therefore to limit growth. After some time, the plant started growing fewer roots and leaves on the side that it had been brushed. The researchers would then remove the plant and placed another in its place. The results showed that the new plant showed the same behavior despite not having been brushed. This was an indication that the former plant had released chemical signals that the new one received and interpreted, responding by producing fewer leaves to avoid the stress. This was validated by using a control group where the plant wasn’t brushed with a brush and was replaced by another plant. The new plant continued to grow as it normally would (5).
All of these findings imply that the attributed idleness to plants is slowly but surely losing its validity. They have different languages to defend themselves and the members of their species, sometimes even making selfish decisions to be the one to survive.
*: Phenolics are aromatic benzene ring compounds with one or more hydroxyl groups produced by plants mainly for protection against stress
**: In physiology, an action potential occurs when the membrane potential, or voltage, of a specific cell location, rapidly rises and falls.
Heil, Martin. “Plant Communication.” ELS, 2009, doi:10.1002/9780470015902.a0021915.
McGowan, Kat, and substantive Quanta Magazine moderates comments to facilitate an informed. “The Secret Language of Plants.” Quanta Magazine, 11 Jan. 2019, www.quantamagazine.org/the-secret-language-of-plants-20131216/.
TEDtalksDirector. “Electrical Experiments with Plants That Count and Communicate | Greg Gage.” YouTube, YouTube, 1 Nov. 2017, www.youtube.com/watch?v=pvBlSFVmoaw.
Ninkovic, Velemir, et al. “Plant Volatiles as Cues and Signals in Plant Communication.” Plant, Cell & Environment, vol. 44, no. 4, 2020, pp. 1030–1043., doi:10.1111/pce.13910.
Elhakeem, Ali, et al. “Aboveground Mechanical Stimuli Affect Belowground Plant-Plant Communication.” PLOS ONE, vol. 13, no. 5, 2018, doi:10.1371/journal.pone.0195646.