Praying Palm and Pavlovian Plants
How experiments conducted 100 years apart are challenging the way we look at intelligence in plants
Starch will have starch
In 1914 a journalist working at the progressive magazine The Nation was invited to witness a series of bizarre experiments conducted by a physicist from India. The demonstrations were held in a small private lab in Maida Vale, an affluent district in West London. What the journalist described was nothing short of a scene from Frankenstein.
“An unfortunate creature is strapped to the table of an unlicensed vivisector. When the subject is pinched with a pair of forceps, it winces. It is so strapped that its electric shudder of pain pulls the long arm of a very delicate lever that actuates a tiny mirror. This casts a beam of light on the frieze at the other end of the room, and thus enormously exaggerates the tremor of the creature. A pinch near the right-hand tube sends the beam 7 or 8 feet to the right, and a stab near the other wire sends it as far to the left.”
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One might wonder whether the scientist succeeded in demonstrating life in a cadaver but it turns out the “unfortunate creature” was but a humble carrot.
Sir Jagadish Chandra Bose’s novel experiments in plant physiology conducted more than a century ago proved that plants respond to physiological stimuli. He invented clever apparatuses such as the crescograph, to accurately measure minuscule movements in plants when subjected to stimulation.
One of his famous papers talked about the curious case of a date palm tree in Faridpur, Bengal. In the evening, when the temple bells would ring, calling the villagers to pray, the tree would prostrate itself. It would then straighten its head in the morning. The tree attracted pilgrims given the miracle. Bose set up his experimental tent at the location and found a strong correlation between temperature and tree movement. Later experiments revealed a causal link: “Rise of temperature was attended by a fall of the tree and vice versâ”.
The Faridpur 'Praying' Palm: the upper photograph shows the position in the morning; the lower position in the afternoon. The two fixed stakes are one meter in height. In front is seen the erect trunk of a different Palm.
There is a revival of such plant physiology experiments with Monica Gagliano of the University of Western Australia and her research team. There are two experimental results that challenge the way we look at memory and stimuli in plants.
The first experiment was to explore the idea of whether plants have long-term memory. The team subjected various specimens of mimosa pudica (touch-me-not plant) to a small external shock. They dropped the plant from a small height onto a foam bed numerous times. After a few attempts, the leaves did not close, suggesting that the plant got accustomed to the stimuli. To verify that it was not a case of “fall fatigue” they administered a greater and different shock and the leaves closed. This is where things got interesting; when the team repeated the small shock treatment after a month, they found that the leaves did not close. In fact, they opened even more widely indicating that the plant had learned that the fall was harmless.
Mimosa Pudica leaves show sensitivity to touch by folding their leaflets. (Photograph by Alamy Blickwinkel) Illustrations of Gagliano’s experimental setup (Krulwich, 2015)
The second experiment is even more curious, where Gagliano extended the Pavlov experiment to plants. In the classic experiment, food was the reward for the dog, and a bell was a cue. The dog learned the association between the ringing of the bell and the presence of food. Gagliano’s team used light as the reward and airflow as the cue. The research team found that when the airflow from a fan conditioned the plants, they would move towards the fan even when there was no light. Just like Pavlov’s dog would salivate when the bell would ring even when there was no food. Plants just like animals can learn from association. The results of this experiment were published in Nature in 2016, indicating a huge win for the field of plant physiology.
Pavlov’s classical conditioning in pea plants, experiment by Monica Gagliano (Gagliano, 2019)
This brings up an interesting question: How do plants without having any brains or neural tissue are able to learn and remember? There are two theories.
The first one is based on calcium-based cellular signaling. Calcium ion is an important messenger molecule involved in many signaling pathways in plants. Changes in calcium concentration have been found to increase in response to many physiological stimuli such as light, touch, plant hormones, and physical stresses such as high salinity, cold, and drought.
The other involves processing information by cells via ion flows. Pioneers in bioelectricity discovered that most plant and animal cells are excitable and electrically active. Neurons in the brain are typically more active and communicate via action potentials - rise and fall in voltage in the cell membrane. It appears plants generate such action potentials as well. The sensitivity is determined by the distribution of ions at the cell periphery, which generates electric potential at the plasma membrane. The carnivorous plant, Venus flytrap needs two repetitive action potentials of its hairs to close the trap and three action potentials to stimulate the digestive gland. It also uses electrical memory to control the behavior of the trap.
Are plants like us? Also, do they like us?
The question of whether plants are conscious has a contentious history. Most scientists considered it a frivolous thought experiment of Orientalists and hippie culture. As a result, J.C. Bose intentionally stayed away from that question. After all, he wanted to be recognized as a serious scientist. He had gained fame for his work as a physicist. He is considered one of the fathers of radio science alongside Tesla, Marconi, and Popov. He was the first Indian to be elected to the Royal Society and the first Indian to receive a US patent. The patent was for a ‘coherer’ (a device that detects radio waves), which Guglielmo Marconi used to build an operational two-way radio. Despite his achievements, Bose was careful not to present himself as an orientalist. The colonial government at the time believed that the East excelled in metaphysical speculations but had no aptitude for science. The idea was rooted in the quack science of phrenology. “The Indian make-up lacked a “bump” and a towering dome-like shape of the Western skull.” This prejudice manifested in his compensation as a professor, which was one-third of what a European received. That is not to say that there were friends, colleagues, and spectators who ignored the question of consciousness in plants.
In one of Bose’s demonstrations at Maida Vale, George Bernard Shaw was brought to tears when he saw how a piece of cabbage in boiling water convulsed violently, based on the readings on Bose’s apparatus. Shaw had been famously vegetarian since the age of 25. He expressed that the line “Never again may blood of bird and beast stain with its venomous stream a human feast” in Shelly’s The Revolt of Islam “opened my eyes to the savagery of my diet.”
Gagliano on the other hand is very vocal in her belief that plants are intelligent having proven that they have the capacity to learn and remember. Critics of Gagliano, very similar to the critics of J.C. Bose, reject the proposition that plants are self-aware. Danny Chamovitz, director of the Manna Center for Plant Biosciences at Tel Aviv University in Israel, argues that plants are neither conscious nor intelligent. All organisms from bacteria to plants to humans are aware of the environment in order to survive. Plants integrate signals from roots, leaves, and flowers and adapt to their surroundings without having a nervous system or a brain. One should not anthropomorphize plants to appreciate their complexity. The crux of the argument lies in the assumption that consciousness is directly connected with the brain, therefore any organism which does not have a brain is not conscious.
The French philosopher Henri Bergson (famous for causing the first traffic jam on Broadway while on his lecture circuit in New York) gave a cogent rebuttal in his book Mind and Brain. Bergson points out the fallacy in the brain-consciousness argument. In humans, digestion is connected to the stomach, does that imply that no other living being can digest? As the complexity of the organism increases, there is a division of labor where special organs get assigned to specific activities. In humans, the brain is indispensable for consciousness. As we go down in the complexity of living things, the nervous systems are simplified and distributed, ultimately merging into the general mass of the organism. “Consciousness is still there, diffused, confused, but not reduced to nothing? Theoretically, then, everything living must be conscious. In principle, consciousness is coextensive with life”.
Bergson argues that the brain is a filtering apparatus for consciousness. Take the example of the famous selective attention test “Gorilla experiment”. Two groups of players pass a basketball to each other and the viewer is asked to keep count. Most viewers completely fail to see a person in a gorilla costume walk past the set. Perception, therefore, is constrained by our motivations. The dominant motivation is the need to survive and the brain is designed to meet that purpose. Therefore Bergson believes that the idea of identifying the brain as the sole source of consciousness is questionable.
Modern-day philosophers such as Michael Marder the author of “Plant Thinking”, subscribe to the same view that the prerequisite for intelligence is having a brain is a very human-centric view. There is evidence of plants communicating between each other (and sometimes with Prince Charles), defending themselves, and making decisions.
The debate boils down to defining intelligence and consciousness. It is interesting to observe how this debate contrasts with the one around Artificial Intelligence. Proponents actively employ human-centric definitions of intelligence to prove sophisticated that data-driven pattern recognition machines, which can generate novel artwork or mimic human conversation, are closer to being sentient. The debate around plant consciousness is more evolved, to say the least.
Hungry for a salad?
What does this mean for humanity? Is eating a salad an act of murder? Is your wooden coffee table a result of genocide? Will plant life exact revenge, just like in M. Night Shyamalan's movie The Happening? Philosophy has a few hints on how to deal with this conundrum.
On one end of the spectrum is Jainism’s core tenant of non-violence. The act of eating can be considered an act of violence. There is a practice called Sallekhana where one fasts to death so as to free oneself of bondage and desire.
On the other end is Herbert Spencer’s (who coined “survival of the fittest”) philosophy of Social Darwinism; where the strong must devour the weak to survive, which is the truth of nature that one must accept. Robin Kimmerer in her book Braiding Sweetgrass: Indigenous Wisdom, Scientific Knowledge and the Teachings of Plants takes a more humanistic take to this. The Native American Potawatomi tribe acknowledges the interdependent relationship between humans and plants. Humans are more than just predators or consumers. The tribe inculcates the culture of a gift economy where an individual gives back to the environment by fostering the growth of the next generation of plants. Each one sacrifices so that the other one survives. It is then not the survival of the fittest but survival by cooperation.
There might be a middle path in this parable from the Indian epic The Mahabharata. During a severe famine, a learned scholar breaks into a dog keeper's house to steal a dog to save himself from starvation. The dog keeper is appalled and argues that it is against the scholar’s code of conduct to eat meat from a forbidden animal such as a dog. The scholar replies that his first duty is to remain alive. It is only when he is alive that he can perform his duties as required by society. In his belief, body and consciousness are different just like skin and sight. While the body is eating the meat, he is self-aware under what circumstances he is eating and can disassociate himself from the moral compunction. Suppose a wise person confronts a calamity and desires to remain alive, as long as they are not miserable in heart, they must cheerfully use every method to save themselves and accept the consequences gracefully. If mankind remains alive, it will obtain what is sacred and is fortunate. In other words, one must be in the world but not of it.
We must allow humanity some exceptions and leeway. Just as we have innovations in vegan meat, one can possibly see a future where there are alternatives to plant and meat-based diets such as nutrition pills and powders. Human civilization should be offered these options and be allowed to adapt their dietary preference as their individual beliefs change slowly.
The Life and Work of Sir Jagadis C Bose: An Indian Pioneer of Science, Patrick Geddes, 1920
Life Movements in Plants Vol 1/The "Praying" Palm Tree, J.C Bose, 1918
Can plants really think? Shutterstock Pavlov’s plants: new study shows plants can learn from experience Prudence Gibson, December 2016
Memory in plants: A new study suggests that plants can remember training, even weeks later, The Economist, Jan 2014
J.C. Bose: Why the great scientist’s legacy remains astonishing a century later Ecologize, Nov 2018
Why JC Bose is feted in India although he was mostly a marginal scientific figure in his lifetime: The polymath encouraged and sometimes even indulged in spiritualist interpretations of his work. Kapil Subramanian, Scroll.in , Nov 2017
J C Bose: The Little Known Story of How India’s First Biophysicist Proved Plants Have Life, Sanchari Pal, BetterIndia, Nov 2016
Are Plants Conscious?, Daniel Kolitz, Gizmodo, May 2018
A debate over plant consciousness is forcing us to confront the limitations of the human mind, Ephrat Livni, Quartz, June 2018
Plant intelligence and the Turing Test, Eugene Wei, Dec 2013
Famous Eaters - George Bernard Shaw, Morning Advertiser, Graham Ridout, Oct 2005
The Intelligent Plant: Scientists debate a new way of understanding flora, Michael Pollan, New Yorker, Dec 2013
Plants and the Memories We Never Knew They Could Have, Alex Conde, INSH, Oct 2017
Whispering of Plants, Shubhankar Kundu, The Qrius Rhino, July 2019
Consciousness, the brain and mystical experience, Zoe Falcone, The Quad, March 2018
Defining Consciousness in Non-neuronal Organisms: Limitations and Possibilities, Dakshitaa Babu, Feb 2021
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