In Lewis Carol’s Through the Looking-Glass and What Alice Found There, when Alice loses her way in a magical flower garden, she turns to a tiger lily and says, “I wish you could talk.” To her astonishment, it replies, “We can talk when there’s anybody worth talking to.” The excerpt though a fantasy, science has proved otherwise, clarifying to the human world that plants can communicate, act, react and send signals, making them more living than just beings with no physical brains. Tracing back in time, the concept of plants having emotions was first discovered in 1848 by Gustav Fechner, an experimental psychologist, who claimed that plants have emotions and can grow better when talked to, given attention and affection. However, life reads differently in a jungle full of trees where they grow together.
The Wood Wide Web
While in the human world, we rely on the internet to communicate with our fellow beings, Peter Wohlleben, a German forester says trees communicate through the Wood Wide Web. He says trees are connected to each other through an underground fungal network. These fungi known as mycorrhizas help share water, nutrients and communicate with other trees about distress signals, diseases, droughts and insect attacks. Besides, trees also identify the similarities and differences in their microbial makeup to recognise trees from their own species and prefer sharing nutrients with them. Scientists call this the ‘Kin Recognition’.
In a paper published in 1997 in Nature, it is suggested that plants do not compete, but cooperate with each other to help the other thrive. Alarm and distress are the prime tree conversations.
Monica Gagliano from the University of Western Australia says some plants emit and detect sounds -- a crackling noise in the roots at a frequency of 220 hertz that is inaudible to humans. They also communicate through the air using scent signals and pheromones. When a lawn is freshly mowed and the air smells thick of cut grass -- a blend of aldehydes, ketones, alcohols and esters -- it is the grass crying out for help signaling its neighbours of danger. Similarly, when a herbivore starts chewing the leaves of a tree/plant, it notices the injury and emits a distress signal in the form of ethylene gas that alerts the neighbouring trees/plants.
The neighbours start pumping tannins into their leaves in large quantities that will shoo away the herbivore. On the other hand, trees also have a sense of taste. Wohlleben writes that when leaves are attacked by leaf-eating caterpillars, they detect the saliva of the caterpillar and release pheromones that attract parasitic wasps. The wasps lay their eggs inside the caterpillars and eat them from the inside out.
Richard Karban, a professor of entomology at the University of California, in one of his experiments, notes that sagebrush plants sound alarms when they are attacked by pests, thus pushing other sagebrush plants to grow faster and stronger.
Besides, flowers also communicate with pollinators through colours, patterns, shapes and fragrances. Researchers at the University of Bristol discovered that bumblebees are positively charged and flowers negatively charged. When a bee sits on a flower, there is an exchange of energy that creates an electric field that the bee feels. Thus, this connection imprints the flower on the bee’s memory, encouraging it to return. Moreover, plants can also listen and respond likewise. Researchers found that pea plants direct their roots towards the sound of moving water, even if it is just a recording and no actual water present. Primrose flowers automatically produce sweeter nectar by the very sound of bees buzzing -- artificial or natural.
Mothering the young
Suzanna Simard from the University of British Columbia who is best known for her research on ‘mother trees’ says these trees are the oldest and biggest in a forest that has a much-advanced fungal network. Though not female trees always, they play the role of a supportive, maternal figure owing to their deep roots that help them draw water to shallow rooted seedlings. They share their excess nitrogen and carbon through mycorrhizal networks with understory seedlings, thus increasing their chances of survival.
They also reinforce their neighbour trees by supplying them nutrients, and when one of them is struggling, mother trees detect the distress signals and supply nutrients accordingly, more like an old mother backing up her young daughters. Mother trees are the central hub in a forest and are connected to hundreds of other trees. However, research makes it clear that kin seedlings receive more carbon from mother trees than stranger seedlings.
From the light of the above findings, it is evident that plants do communicate with each other.
Planting thoughts
1. A plant communicates with other roots of the same plant or with those of other plants by means of electrical signals, which helps it distinguish friend from foe
2. The root tips of a plant are highly mobile. They cover vast distances through minerals, microbes and varying degrees of moisture, gathering information as they go
3. They use their roots to ‘listen in’ on their neighbours. Plants that grow in a crowded environment secrete chemicals into the soil to prompt their neighbours to grow aggressively and to avoid being left behind
4. Charles Darwin and his son Francis discovered that roots can sense gravity, light, moisture, pressure and other environmental factors, and would choose the best route based on the information they gather
5. Sir Jagadish Chandra Bose invented ‘Crescograph’ and made pioneering discoveries in plant physiology and plant response to stimuli
Human-like emotions?
Experts believe that the Soul-life Theory dates back to 1848 in a book called Nanna (Soul-life of Plants), in which German psychologist Gustav Fechner suggested that plants might be capable of feeling emotions akin to human beings. However, we do not know for a fact that plants respond to affection.