When I am walking through a forest, I feel like I am entering a fairytale where I start visualizing trees that talk to each other and might start walking any minute. And then I realize that I might be fantasizing too much! But what if a part of this fantasy is true? That trees may actually be communicating with each other in a way we can’t perceive.
Unbelievable as it may sound, scientists have found that inter-plant signaling occurs via three routes: roots, foliage and airborne signaling. For example, willow trees release volatile organic compounds when an herbivore is chomping on them, warning their neighbors of the upcoming threat. This phenomenon of releasing a cue is also seen in Acacia trees in the savannas that release ethylene gas when eaten by giraffes. The gas can travel up to 50 yards and, within 5-10 minutes, induces increased tannin production in the leaves of neighboring trees, making them highly unpalatable and dangerous for the animals. Unfortunately, the giraffes have learnt this trick and start grazing upwind as they progress.
There are other examples of trees sending each other signals when danger is near. Peter Wohlleben, a German forester and author, acknowledges that trees have a sense of taste and can detect scents through their leaves. When elms and pines come under attack by leaf-eating caterpillars, their leaves detect caterpillar saliva and release pheromones that attract parasitic wasps. These wasps lay their eggs inside the caterpillars, which then serve as food for the hatching larvae. Behold, the trees take their revenge in a very unpleasant, but clever way! A study from Leipzig University and the German Centre for Integrative Biodiversity Research shows that trees can distinguish between a deer biting a branch and a human breaking it with hands. Fascinatingly, trees can “taste” deer saliva and respond by producing defending chemicals which make the leaves unappetizing; whereas, in the latter case, trees bring substances to heal the wound.
You may have read about mycorrhizae-fungal networks entwined in a symbiotic relationship with roots of trees connecting them underground. The fungi consume about 30% of the sugars photosynthesized by the trees, and in exchange provide nitrogen, phosphorus and other mineral nutrients to the plants. Intriguingly, the mycorrhizae also act as an “organic internet”, allowing trees to communicate. A large portion of trees in a forest are connected through the same mycorrhizal network and exchange sugars, chemicals and electrical signals. These plant-fungal-plant interactions provide feedbacks and comprise a complex adaptive social network, which is very rapid. Suzanne Simard and her fellow researchers have done extensive research on mycorrhizal networks (suggested reading- Teste FPet al 2009), and using seedlings, have shown that trees recognize root tips of their kins over the root tips of unrelated seedlings. Simard calls the largest and eldest trees as “mother trees”, which protect and nurture the surrounding younger trees by sharing resources and acting as vital defense systems. For young saplings in a shady forest, this network literally acts as a lifeline as the big trees pump sugar into their roots through this fungal network. The “mother trees” have even been shown to preferentially identify young trees of their own species, and send them a larger serving of sugars via the fungal network.
Over the years, scientists have deciphered different ways of plant communication, however, there is still much more to be unveiled. Recent studies have identified biochemical signaling and resource transfer (suggested reading- Islam E et al 2015; Francis and Read 1984; Simard SW et al 1997 a.b; He et al 2009) as important means of communication amongst trees. It is astonishing to learn how a gigantic beech stump in a forest, with its bark felled 400 or 500years ago, could show the presence of green chlorophyll upon being scraped. It could only happen when the surrounding beeches were keeping it alive by pumping sugars to it through the network. And why would they do so? Probably, to keep living with their big, old revered matriarch for few more years.
It is important to understand that scientists have never claimed that trees have consciousness or intention, but trees certainly have a type of intelligence which has allowed them to thrive for years.It is tragic that lumbering practices in many parts of the world have disrupted years of forest networks through deforestation. We need to inculcate practices which minimize forest damage, for example, use of horses for tree felling and being conscientious to the surrounding forest. It would be best if more wood substitutes could be used which would significantly bring down deforestation. For example, bamboo is now becoming increasingly popular alternative for flooring and furniture due to its high resilience and easy maintenance. Paper wastage can be reduced by recycling books, using libraries and e-books. After all, sitting peacefully under a large tree does create a magical effect!
Author:
Piyushi Gupta Vallur is a scientific writer (freelancer) at Course5i, Bengaluru, a data analytics and insights firm. She has a Ph.D. in Neuroscience from National Brain Research Centre, India. It is at this place where she got her first training in documenting research findings in a scientific and intelligible manner; all the way being encouraged by her mentor, Dr. Ellora Sen. She did her post-doctorate in ovarian cancer at Pennsylvania State University, where she further got opportunities to write scientific manuscripts, review articles and grant fellowships; while simultaneously learning and strengthening her literary skills. Being a researcher, she always emphasizes on the scientific evidence behind an interesting story. She believes knowledge can be shared in a simple and uncomplicated way by presenting the facts in an interesting, but untwisted manner.
Editors:
Ananya Sen is currently a science writer at the Carl R. Woese Institute for Genomic Biology. She completed her Ph.D. in Microbiology at the University of Illinois at Urbana-Champaign in 2021. She is an ardent reader and will happily discuss anything from Jane Austen to Gillian Flynn. Her travel goals include covering all the national parks in the U.S. with her sidekick Oscar, a Schnauzer/Pomeranian mix.
Sumbul Jawed Khan received her Ph. D. in Biological Sciences and Bioengineering from the Indian Institute of Technology Kanpur, where she studied the role of microenvironment in cancer progression and tumor formation. During her post-doctoral research at the University of Illinois at Urbana-Champaign, she investigated the gene regulatory networks that are important for tissue regeneration after damage or wounding. She is committed to science outreach activities and believes it is essential to inspire young people to apply scientific methods to tackle the challenges faced by humanity. As an editor, her aim is to simplify, translate, and excite people about current advances in science.
Illustrator:
Disha Chauhan did her Ph.D. in IRBLLEIDA, University of Lleida, Spain in Molecular and Developmental Neurobiology. She has post-doctoral experience in Cell Biology of Neurodegenerative diseases and is actively seeking a challenging research position in academia/industry. Apart from Developmental Neurobiology, she is also interested in Oncology. She is passionate about visual art (Illustration, painting, and photography) and storytelling through it. She enjoys reading, traveling, hiking, and is also dedicated to raising scientific awareness about Cancer. Follow her on Instagram.
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