Is it possible that plants have feelings too and if so what proof is there? With the controversial field of plant neurobiology igniting opinions, Jade Norton leafs you wondering what the future may hold for plant cognitive research.

We live in a world that is increasingly aware and sensitive towards other people’s feelings and attitudes, but have we forgotten about the plants? There has been increasing controversy over the possibility of plant sentience and consciousness with fields such as plant neurobiology and plant cognitive ecology questioning do plants have a neural network and is their behaviour based on an ability to learn and remember responses to stimuli. In a recent study by Lincoln Taiz he unapologetically denies any trace or requirement of consciousness in plant life.

Another critic is Monica Galgiano who doesn’t believe that plants have the same neural networks as animals but does believes that plants may be capable of learned behaviour and she terms this plant cognitive ecology. However, this is not the first examination on plant cognition as back in 1973 the “infamous” The Secret Life of Plants was released by Peter Tompkins and Christopher Bird and documented their controversial experiments that claimed to reveal plant sentience. Generally regarded with scepticism by scientists due to a lack of evidence, plant consciousness has the possibility of being a hidden phenomenon in front of us all but if it does turn out to have scientific basis, what would that mean for the future of the planet and our relationship with the organisms that are essential for our survival.

The Secret Life of Plants is a book that uses the works of 19th and 20th century plant scientists such as Dr J.C Bose and George Washington Carver to claim that plants had emotions and sentience. In 1925, plant scientist Dr J.C Bose was fascinated with the strange and unusual behaviour of plants in response to stimuli and set up many experiments to show that electrical signals were present in plants. His invention of the Crescograph allowed the measurement of plant responses to stimuli and scientifically proved parallelism between plant and animals’ tissues. However, his work was denied publication by the Royal Society as it was seen as absurd that “normal” plants could share electrical signals similar to that of more complex animals.

The first ever discovery of electrical signals in plants was recorded by Pierre Bertholon de Saint-Lazare in 1783 and Burdon-Sanderson and Darwin also used this idea in their experiments in the early 1870s and it led to the general acceptance of electrical signals in unusual plants such as the Venus fly trap and mimosa pudica. 

However, The Secret Life of Plants correlated electrical signals to evidence of consciousness, and this cast doubt on whether electrical signals were in fact present in “normal” plants rather than just in the more unusual plants. This captured the mainstream audiences’ imagination and effectively caused an impasse in funding for electrophysiology research in plants in the US as it promoted pseudoscience claims that were irreproducible. This fuelled the assumption that electrical signals were not needed in plants as they were sluggish, sedentary and definitely not emotional. This stigmatised all future experiments in plant cognition including plant neurobiology.

Plant neurobiology as field of study that started to gain traction in 2006 from a paper by Dr Eric Brenner that claims that the electrical signals given off by plants as a means of intracellular communication can be compared to the neural network in animals. This has parallels to the research from The Secret Life of Plants but with reproducible experiments. The paper compared elements of the internal physiology of plants such as auxin transport, to animal neurotransmitters and glutamate signalling, to the firing of an action potential in the animal neuronal cell. Auxin is used to regulate the growth of plants and is influenced by trophic conditions such as phototropism, where plants grow towards the sun and thigmotropism as seen in the mimosa pudica where the plant responds to physical contact. Plants also release chemical pheromones that can warn nearby plants of a danger or induce a chemoattraction/movement towards a plant of the opposite sex. All these behaviours are plants experiencing a stimulus and reacting to it. This allowed plant neurobiologists to infer that plants have, at a molecular level, all the components of an animal neuronal system. From this it can be interpreted that plants are experiencing a consciousness as a culmination of reactions associated with stimuli that create a mental mapped image in a sensory dimension just like in an animal.

There is a strong argument against the plant neurobiologists, stating that plants are stationary organisms that do not have a need for consciousness as it would not aid their existence but would rather be a drain on resources that could be being used to create energy to survive with instead. This is the basis of opinion piece by Lincoln Taiz in Trends in Plant Science that uses a particularly grim example of the ineffectiveness of consciousness for plants in a forest fire.

The plant in the forest is anchored in the earth yet must observe the deathly fire knowing that it has no mechanisms of survival and if it is lucky to survive it will be riddled with grief from the death of the surrounding plants. There is no evolutionary advantage to having feelings in this situation or even the ability to react because plants cannot move at the speed that would aid their survival.

In response to the idea that plants have their own version of neurons Taiz believes that the experiments are too one sided. The experiments look at the physiology of plants and try to infer their relationship to consciousness by seeing molecules that do the same things without reasoning why they do it.

Whether plants have consciousness or not is still contested with two sides of the debate certain of their hypothesis. To fundamentally agree that plants have cognitive ability would require a change in the established convention. Taking the plants feelings into consideration would mean that experiments involving plants and even the idea of commercial forests would have to be reevaluated.

The current mindset of established scientists is that plant consciousness or cognition is an anthropomorphism of plant biology but throughout history hypotheses have been dismissed for going against the status quo. This happened with Barbara McClintock who was dismissed for her experiments into the movement of genes in corn genomes only to be awarded a Nobel Prize for her work 50 years after her initial discovery, so there is still hope for the plant neurobiologists should they find definite proof of plant cognition. Despite this, the answers would still lead to more questions, but it may lead to a world that cares more for the environment when it knows if it feels.