The notion that plants are capable of feeling emotions was first recorded in 1848, when Gustav Fechner, a German experimental psychologist, suggested that plants are capable of emotions and that one could promote healthy growth with talk, attention, attitude, and affection. Indian scientist Jagadish Chandra Bose, began to conduct experiments on plants in the year 1900. Bose invented various devices and instruments to measure electrical responses in plants. He stated from his experiments that an electrical spasm occurs during the end of life for a plant. According to biologist Patrick Geddes "In his investigations on response in general Bose had found that even ordinary plants and their different organs were sensitive— exhibiting, under mechanical or other stimuli, an electric response, indicative of excitation." One visitor to his laboratory, the vegetarian playwright George Bernard Shaw, was intensely disturbed upon witnessing a demonstration in which a cabbage had "convulsions" as it boiled to death.
Later research
In the 1960s Cleve Backster, an interrogation specialist with the CIA, conducted research that led him to believe that plants can communicate with other lifeforms. Backster's interest in the subject began in February 1966 when he tried to measure the rate at which water rises from a philodendron's root into its leaves. Because a polygraph or 'lie detector' can measure electrical resistance, which would alter when the plant was watered, he attached a polygraph to one of the plant's leaves. Backster stated that, to his immense surprise, "the tracing began to show a pattern typical of the response you get when you subject a human to emotional stimulation of short duration". In 1975, K. A. Horowitz, D. C. Lewis and E. L. Gasteiger published an article in Science giving their results when repeating one of Backster's effects - plant response to the killing of brine shrimp in boiling water. The researchers grounded the plants to reduce electrical interference and rinsed them to remove dust particles. As a control three of five pipettes contained brine shrimp while the remaining two only had water: the pipettes were delivered to the boiling water at random. This investigation used a total of 60 brine shrimp deliveries to boiling water while Backster's had used 13. Positive correlations did not occur at a rate great enough to be considered statistically significant. Other controlled experiments that attempted to replicate Backster's findings have also produced negative results. Botanist Arthur Galston and physiologist Clifford L. Slayman who investigated Backster's claims wrote:
There is no objective scientific evidence for the existence of such complex behaviour in plants. The recent spate of popular literature on "plant consciousness" appears to have been triggered by "experiments" with a lie detector, subsequently reported and embellished in a book called The Secret Life of Plants. Unfortunately, when scientists in the discipline of plant physiology attempted to repeat the experiments, using either identical or improved equipment, the results were uniformly negative. Further investigation has shown that the original observations probably arose from defective measuring procedures.
John M. Kmetz noted that Backster had not used proper controls in his experiments. When controls were used, no plant reactions to thoughts or threats were observed. The television showMythBusters also performed experiments to verify or disprove the concept. The tests involved connecting plants to a polygraph galvanometer and employing actual and imagined harm upon the plants or upon others in the plants' vicinity. The galvanometer showed a reaction about one third of the time. The experimenters, who were in the room with the plant, posited that the vibrations of their actions or the room itself could have affected the polygraph. After isolating the plant, the polygraph showed a response slightly less than one third of the time. Later experiments with an EEG failed to detect anything. The show concluded that the results were not repeatable, and that the theory was not true. Daniel Chamovitz's 2012 book, What a Plant Knows, reevaluates plant senses from a scientific perspective.
