Underground plant communication is a relatively new field of study that continues to uncover fascinating behavioural traits of a plant's ability to communicate with what is around it. In the previous presentations, plant senses and airborne communication were discussed. In this presentation, the focus is on underground communication.
Underground plant communication has been making headlines in the world of natural sciences for the last few years. To many in the past, this concept has been perceived as a pseudoscience without credible data. However, the last decade has provided irrefutable evidence of this natural phenomenon which has opened up another world of questions and inquiry. The base premise of the findings states that most plants root systems have a mutualistic relationship with fungal mycelium networks that span across extensive areas. It is these networks that allow plants to exchange information and various resources over vast distances. This connected system is known as a mycorrhizal network and plays a vital role in the health of a natural plant system.
The mycorrhizal network is comprised of a variety of plant and fungal species that allow for all connected plants to form an adaptive social network. Most of the relationships between the plant hosts and fungal mycelium is diffuse, meaning that the relationships are not species specific. Thus allowing for a larger mycorrhizal network to connect a broad spectrum of plant species. Some mycorrhizal fungi, however, are specialists that focus on particular species of plants. This network influences plant survival in various ways, such as influencing growth, health, physiology and behavioural patterns of plants. Before delving deeper into how and why this network functions the way it does, let us briefly look at how this was discovered.
The primary credit for this discovery goes out to a forest ecologist by the name of Prof. Suzzane Simand. By conducting large-scale field research in pristine Canadian forests, Prof. Simand found that there was indeed interaction between various plants through the mycorrhizal network. Her method was to seal smaller trees in various locations in plastic and inject tracer isotopes into the sealed bag. While other small trees were covered in shade netting in order to hamper their own carbon production.
The isotopes she used were radioactive carbon-14 carbon dioxide gas and the stable isotope carbon-13 carbon dioxide gas. By using two different tracer isotopes, she could determine whether there is indeed an exchange and if it is one way or dynamic. By using a Geiger counter on plants that were not initially exposed to the tracer isotopes, she found that indeed within an hour, the isotopes had been transferred from one plant to its neighbour covered in shade cloth who required carbon. She discovered that this communication is cross species, in this case from a birch to a fir tree, but that the species that were not linked to the mycorrhizal network did not receive the isotope, in this case, a cedar tree. The two different isotopes also indicated that the communication is of a dynamic back and forth kind.
Multiple resources are transferred through the mycorrhizal network to other plants, this includes water, carbon, phosphorus, nitrogen, stress chemicals, allelochemicals (harmful chemicals) and other micronutrients. This is believed to be a source-sink relationship, where plants that have an abundance of certain chemicals become 'donor' plants, while those that are in need become the 'receiver' plant. In this way, the relationship is far more mutualistic between most plants in the forest, instead of being dominantly driven by competition as previously thought. In fact, areas with a diversity of plant and fungal species are far more healthy than those of any monoculture, which require far more maintenance and use of harmful agricultural methods. An interesting note is that the oldest trees, named 'mother' trees are the primary providers of chemical signals and resources to other plants in the area. And that while this relationship may positively affect most plants in the area, there is a clear preference for them to look after their own offspring saplings, even if they are not close to their parent tree. Thus, the biggest mistake of the forestry industry is the cutting down of the large 'mother species'.
Much more can be said about this fascinating communication network, so I encourage anyone who has a mind and heart for nature to delve further into this subject. This immense breakthrough has the potential to change the agricultural and forestry sphere into one that is more holistic, sustainable and cost-effective than our current practices. I look forward to seeing what else this field uncovers in the future.