WHEN I FIRST ENCOUNTERED the works of Sir Jagadis Chunder Bose, I was stunned. The son of a public official in East Bengal, Bose was educated in Cambridge, where he received a degree in natural science that he took back to his home country. A genius in both physics and botany, he had an extraordinary eye for detail as well as a unique talent for designing precision measuring equipment. With an intuition that all living things share the same fundamentals, this man built elegant machinery that could magnify the movements of ordinary plants one hundred million times, while recording such movements automatically, and he proceeded in this way to study the behavior of plants in the same manner that zoologists study the behavior of animals. In consequence, he was able to locate the nerves of plants—not just unusually active plants like Mimosa and Venus fly trap, but “normal” plants—and he actually dissected them out and proved that they generate action potentials like any animal’s nerves. He performed conduction experiments on the nerves of ferns in the same way physiologists do with the sciatic nerves of frogs.
Sir Jagadis Chunder Bose (1858-1937)
Bose also located pulsating cells in a plant’s stem which he showed are responsible for pumping the sap, which have special electrical properties, and he built what he called a magnetic sphygmograph that magnified the pulsations ten million times and measured changes in sap pressure.
I was astonished, because you can search botanical textbooks today without finding so much as a hint that plants have anything like a heart and a nervous system. Bose’s books, including Plant Response (1902), The Nervous Mechanism of Plants (1926), Physiology of the Ascent of Sap (1923), and Plant Autographs and Their Revelations (1927), languish in the archives of research libraries.
But Bose did more than just find the nerves of plants. He demonstrated the effects of electricity and radio waves on them, and he obtained similar results with sciatic nerves of frogs, proving the exquisite sensitivity of all living things to electromagnetic stimuli. His expertise in these areas was beyond question. He had been appointed Officiating Professor of Physics at the Presidency College in Calcutta in 1885. He made contributions in the field of solid-state physics, and is credited with the invention of the device—called a coherer—that was used to decode the first wireless message sent across the Atlantic Ocean by Marconi. In fact, Bose had given a public demonstration of wireless transmission in a lecture hall in Calcutta in 1895, more than a year before Marconi’s first demonstration on Salisbury Plain in England. But Bose took out no patents, and sought no publicity for his invention of the radio. Instead he gave up those technical pursuits to devote the rest of his life to the more humble study of plant behavior.
In applying electricity to plants, Bose built on a tradition that was already a century and a half old.
The first to electrify a plant with a friction machine was a Dr. Mainbray of Edinburgh, who connected two myrtle trees to a machine throughout October 1746; the two trees sent out new branches and buds that autumn as though it were springtime. The following October, Abbé Nollet, having received this news, conducted the first of a series of more rigorous experiments in Paris. In addition to Carthusian monks and soldiers of the French guard, Nollet was electrifying mustard seeds as they sprouted in tin bowls back in his laboratory. The electrified sprouts grew four times as tall as normal, but with stems that were weaker and more slender.1
That December, around Christmas time, Jean Jallabert electrified jonquil, hyacinth, and narcissus bulbs in carafes of water.2 The following year Georg Bose electrified plants at Wittenberg,3 and Abbé Menon at Angers,4 and for the rest of the eighteenth century plant growth demonstrations were de rigeur among scientists studying frictional electricity. The energized plants sprouted earlier, grew faster and longer, opened their flowers sooner, sent out more leaves, and were generally—but not always—sturdier.
Jean-Paul Marat even watched electrified lettuce seeds germinate in the month of December when the ambient temperature was two degrees above freezing.5
Giambattista Beccaria in Turin was the first, in 1775, to suggest the use of these effects for the benefit of agriculture. Soon afterwards Francesco Gardini, also in Turin, stumbled upon the opposite effect: plants deprived of the natural atmospheric field did not grow as well. A network of iron wires had been stretched over the ground for the purpose of detecting atmospheric electricity. But the wires happened to run above part of a monastery’s garden, shielding it from the atmospheric fields that the wires were measuring. For the three years that the wire net had been in place, the gardeners tending that section had complained that their harvests of fruits and seeds were fifty to seventy percent less than in the rest of their gardens. So the wires were removed, and production returned to normal. Gardini drew a remarkable inference. “Tall plants,” he said, “have a harmful influence on the development of plants that grow at their base, not only by depriving them of light and heat, but also because they absorb atmospheric electricity at their expense.”6
In 1844, W. Ross was the first of many to apply electricity to a field of crops, using a one-volt battery much like the one from which Humboldt had so successfully elicited sensations of light and taste, only larger. He buried a copper plate five feet by fourteen inches at one end of a row of potatoes, a zinc plate two hundred feet away at the other end, and connected the two plates with a wire. And in July he harvested potatoes averaging two and a half inches in diameter from the electrified row, versus only one-half inch from the untreated row.7
In the 1880s, Professor Selim Lemström of the University of Helsingfors in Finland conducted large-scale experiments on crops with a friction machine, suspending over his crops a network of pointed wires connected to the positive pole of the machine. Over a period of years he found that electricity stimulated the growth of some crops—wheat, rye, barley, oats, beets, parsnips, potatoes, celeriac, beans, leeks, raspberries, and strawberries—while it stunted the growth of peas, carrots, kohlrabi, rutabagas, turnips, cabbages, and tobacco.
And in 1890, Brother Paulin, Director of the Agricultural Institute at Beauvais, France, invented what he called a “géomagnétifère” to draw down atmospheric electricity like Benjamin Franklin had once done with his kite. Perched atop a tall pole 40 to 65 feet high was an iron collecting rod, terminating in five pointed branches. Four such poles were planted on every hectare of land, and the electricity collected by them was carried to the soil and distributed to the crops by means of underground wires.
According to contemporary newspaper accounts the effect was visually startling. Like supercrops, all of the potato plants within a sharply delineated ring were greener, taller, and “twice as vigorous” as the surrounding plants. The yield of potatoes within the electrified areas was fifty to seventy percent greater than outside them. Repeated in a vineyard, the experiment produced grape juice with seventeen percent more sugar, and wine with an exceptional alcohol content. Further trials in fields of spinach, celery, radishes, and turnips were just as impressive. Other farmers, using similar apparatus, improved their yields of wheat, rye, barley, oats, and straw.8
All these experiments with frictional electricity, feeble electric batteries, and atmospheric fields might make one suspect that it doesn’t take very much current to affect a plant. But until the end of the nineteenth century the experiments lacked precision, and accurate measurements were not available.
Which brings me back to Jagadis Chunder Bose.
In 1859, Eduard Pflüger had formulated a simple model of how electric currents affect animal nerves. If two electrodes are attached to a nerve and the current is suddenly turned on, the negative electrode, or cathode, momentarily stimulates the section of nerve near it, while the positive electrode, or anode, has a deadening effect. The reverse occurs at the moment the current is broken. The cathode, said Pflüger, increases excitability at “make,” and decreases excitability at “break,” while the anode does just the opposite. While the current is flowing and not changing, supposedly nervous activity is not affected whatsoever by the current. Pflüger’s Law, formulated a century and a half ago, is widely believed until the present day, and is the basis for modern electrical safety codes that are designed to prevent shocks at “make” or “break” of circuits but that do not prevent low-level continuous currents from being induced in the body because they are presumed to be of no consequence.
Unfortunately Pflüger’s Law is not true and Bose was the first to prove it. One problem with Pflüger’s Law is that it was based on experiments using relatively strong electric currents, on the order of one milliampere (a thousandth of an ampere). But, as Bose showed, it is not even correct at those levels.9 Experimenting on himself in much the same way Humboldt had done a century before, Bose applied an electromotive force of 2 volts to a skin wound, and to his surprise the cathode, both at make, and as long as the current flowed, made the wound much more painful. The anode, both at make and while the current flowed, soothed the wound. But exactly the opposite occurred when he applied a much lower voltage. At a third of a volt, the cathode soothed and anode irritated.
After experimenting on his own body, Bose, being a botanist, tried a similar experiment on a plant. He took a twenty-centimer length of the nerve of a fern, and applied an electromotive force of only a tenth of a volt across the ends. This sent a current of about three ten-millionths of an ampere through the nerve, or about one thousand times less than the range of currents most modern physiologists and makers of safety regulations are used to thinking about. Again, at this low level of current, Bose found precisely the reverse of Pflüger’s Law: the anode stimulated the nerve and the cathode made it less responsive. Evidently, in plants as well as in animals, electricity could have exactly opposite effects depending on the strength of the current.
Still Bose was not satisfied, because under certain circumstances the effects did not consistently follow either pattern. Maybe, suspected Bose, Pflüger’s model was not only wrong but simplistic. He speculated that the applied currents were actually altering the conductivity of the nerves and not just the threshold of their response. Bose questioned the received wisdom that nervous functioning was a neat all-or-nothing response based only on chemicals in a watery solution.
His ensuing experiments confirmed his suspicions spectacularly. Contrary to existing theories—existing still today in the twenty-first century—of how nerves function, a constantly applied electric current, even though tiny, profoundly altered the conductivity of the animal and plant nerves Bose tested. If the applied current was in the same direction as nervous impulses, the speed of the impulses became slower and, in the animal, the muscular response to stimulation became weaker. If the applied current was in the opposite direction, nervous impulses traveled faster and muscles responded more vigorously. By manipulating the magnitude and direction of the applied current, Bose found that he could control nerve conduction at will, in animals and in plants, making nerves more or less sensitive to stimulation, or even blocking conduction altogether. And after the current was turned off, a rebound effect was observed. If a given amount of current depressed conduction, the nerve became hypersensitive after it was turned off, and remained so for a period of time. In one experiment a brief current of 3 microamperes—3 millionths of an ampere—produced nervous hypersensitivity for 40 seconds.
An incredibly tiny current was all that was needed: in plants, one microampere, and in animals a third of a microampere, was enough to slow or speed up nerve impulses by about twenty percent.10 This is about the amount of current that would flow through your hand if you touched both ends of a one-volt battery, or that would flow through your body if you slept under an electric blanket. It is much less than the currents that are induced in your head when you talk on a cell phone. And, as we will see, it requires even less current to affect growth than to affect nerve activity.
In 1923, Vernon Blackman, an agricultural researcher at Imperial College in England, found in field experiments that electric currents averaging less than one milliampere (one thousandth of an ampere) per acre increased the yields of several types of crops by twenty percent. The current passing through each plant, he calculated, was only about 100 picoamperes—that’s 100 trillionths of an ampere, about a thousand times less than the currents Bose had found were necessary to stimulate or deaden nerves.
But the field results were inconsistent. So Blackman took his experiments into the laboratory where both exposure and growth conditions could be precisely controlled. Barley seeds were sprouted in glass tubes, and at varying heights above each plant was a metal point charged to about 10,000 volts by a DC power supply. The current flowing through each plant was measured precisely with a galvanometer, and Blackman found that a maximal increase in growth was obtained with a current of only 50 picoamperes, applied for just one hour per day. Increasing the time of application diminished the effect. Increasing the current to a tenth of a microampere was always harmful.
In 1966, Lawrence Murr and colleagues at Pennsylvania State University, experimenting on sweet corn and bush beans, verified Blackman’s finding that currents around one microampere inhibited growth and damaged leaves. They then took these experiments one step farther: they undertook to discover the smallest current that would affect growth. And they found that any current greater than one quadrillionth of an ampere would stimulate plant growth.
In his radio experiments, Bose used a device he called a magnetic crescograph, which recorded the growth rate of plants, magnified ten million times.11 Remember that Bose was also an expert in wireless technology. When he set up a radio transmitter at one end of his property, and a plant attached to a receiving aerial at the other end, two hundred meters away, he found that even a brief radio transmission changed a plant’s growth rate within a few seconds. The broadcast frequency, implied from his description, was about 30 MHz. We are not told what the power was. However, Bose recorded that a “feeble stimulus” produced an immediate acceleration of growth, and that “moderate” radio energy retarded growth. In other experiments he proved that exposure to radio waves slowed the ascent of sap.12
Bose’s conclusions, drawn in 1927, were striking and prophetic. “The perceptive range of the plant,” he wrote, “is inconceivably greater than ours; it not only perceives, but also responds to the different rays of the vast aetherial spectrum. Perhaps it is as well that our senses are limited in their range. For life would otherwise be intolerable under the constant irritation of these ceaseless waves of space-signalling to which brick walls are quite transparent. Hermetically-sealed metal chambers would then have afforded us the only protection.”13