June 1971 Popular Electronics
Table of Contents
Wax nostalgic about and learn from the history of early electronics. See articles
published October 1954 - April 1985. All copyrights are hereby acknowledged.
Exploiting the electronic
nature of living organisms through contrived application and manipulation of electric
currents has been a goal of researchers (and quacks) ever since
Luigi Galvani first discovered that connecting a battery lead
to a frog's leg would cause it to kick.
Psychogavanic reflex (PGR) is the technical term for the science.
Once it was determined that all forms of fauna would respond to electrical stimulation,
it wasn't long before the same sort of treatment was applied to all forms of flora.
Many people (not me, for the record*) believe that talking to plants can influence
their health and growth, so why not - so goes the reasoning - try electric currents
as well. We all know from spy, war, sci-fi, and horror movies that under the right
conditions some pretty extreme responses can be provoked with judicious applications
of currents through select portions of the human body. Do plants emit silent screams
when experiments go too far? Interestingly - even creepily - mention is made of
Mr. Cleve Backster (in honor of whom the term "Backster Effect" is coined), who was a CIA (Central Intelligence
Agency) polygraph expert that plied his knowledge of electric currents in living
tissue to the cause of plant electroculture. He may have even applied lessons learned
from plant shocking to humans, not that I'm implying so.
* I will concede that perhaps the extra does of carbon dioxide from breath may
provide a small boost to a plant's metabolism.
More Experiments in Electroculture
Do They Really Know If You Care?
Find Out Electronically
Experimenting on living organisms is exciting and - as history shows - often
rewarding. But there just aren't many people, dogs, birds, fish, etc., that you
can (or would want to) subject to tests to determine such things as emotional reactions,
nervous response, or sensorial perception. So, how about plants? They are after
all, living things, and there are many indications that when stimulated, they have
sensitive, sensible reactions which can be measured on ordinary electronic equipment.
Before going into the details of the equipment (which you can build for yourself),
let's get to know a little more about plants and how they tick.
Do They Just Sit? On first thought, plants appear to be quite
remote from life as we know it. Their sedentary existence stands in strong contrast
to energetic animals, which are endowed with a massive inventory of sensory capacities,
fast reflex movements, and many active organs.
However, recent research has revealed that many of the same environmental factors
and stimulations that affect animals also affect plants. Of course, here we find
modified abilities to sense, feel, and react. Also, since a plant cannot run away
from a threat to its existence, it would appear that special internal forces are
set in motion to protect the organism from shock and possible death. These phenomena
are akin to states of anxiety in animals and are evidenced by changes in the plant's
psychogalvanic or electric states which occur in threatening situations. The recently
discovered "Backster Effect," seems to provide evidence that plants have some ability
to function in a mode of supersensory perception. This, of course, invites a host
of exciting and unique investigations.
Fig. 1 - If desired, the circuit can be terminated at meter M1
if you just want meter readout, or you can drive the audio oscillator with headphones
connected to the 8-ohm output and the meter out of the circuit. However, for maximum
versatility, the entire circuit can be built and both an audio and dc recorder used.
However, prior to engaging in plant-oriented experiments, you should realize
that living systems frequently produce maverick results. While a plant may be regarded
as an organic semiconductor haying variable resistance and self-generating properties,
it also has elements of apparent cellular consciousness. Electronic and mechanical
response profiles are not uniform.
Some plants (such as the Mimosa Pudica) react rapidly; others give no discern
able reactions to stimuli and still others exhibit strangely delayed responses.
Remember that typical electrical signals provided by plants are in the low millivolt/microampere
range. The equipment described here for making experiments should give you a good
start, but for some extremely sensitive tests, you should avail yourself of an ultra-high-gain
electrometer with input impedances of 1010 ohms or higher.
Another factor to remember is the importance of repetition. If, fur example,
a plant specimen is stimulated continuously, badly injured by burns or cuts, infrequently
watered, etc., it is bound to tire quickly, perhaps lapse into shock and die. Terminal
conditions are indicated by wilting, and discoloration usually forecasts death.
Depending on the plant's overall chemistry and the amount of moisture retained in
leaves and stem structures, a dead specimen is little else than a simple conductor
of the carbon typo and no psychogalvanic response of any kind should be expected.
In short, be gentle and allow plants to recuperate after they have served your purpose.
The behavior of plants in strong r-f fields has been studied only superficially.
Although excessive energy levels induce heating and death and although plants are
(electrically speaking) dc-oriented organisms, they nevertheless incorporate mechanisms
which allow them to survive in the immediate vicinity of high-power radio transmitters
of all types. To our knowledge, no tests have been performed to detect psychogalvanic
behavior in plants under these conditions.
Some 350,000 plant species are known to science. At this time, we have no concise
information as to which group is psvchogalvanically superior to others. In general,
however, it has been discovered (Lund, 1931) that the distribution of gradients
of electrical potentials in large plants (such as trees) is more complex than in
small plants. Apparently, each individual cell in a plant is electrically polarized
and acts as a tiny, variable battery. The electrical potentials occurring in tissues
are summation effects of the potentials of individual cells which may act either
in series or in parallel (Rosene, 1935). Various mechanisms of correlation are involved
here; but, as you are bound to discover, there is no complete uniformity from one
specimen to the next, either in looks or reactions.
Plant Response Detector. The basic instrument for plant experimentation
is a response detector whose schematic is shown in Fig. 1. The detector has both
visual (meter) and acoustical (speaker) indications of plant reaction. The audio
tone output can also be connected to a conventional audio tape recorder and a pen-type
recorder can be connected to the dc amplifier output to make permanent records of
The schematic is divided into four operational sections: the Wheatstone bridge
input with exciter and input-output polarizer; an op amp guard circuit having a
disabling feature; a high-gain dc operational amplifier; and an audio tone generator
whose frequency varies with the potential generated in the plant. The op amp used
has a large-signal gain of 100,000 and has built-in short circuit protection.
The circuit can be assembled on perf board or a printed circuit board. Be careful
to avoid heat damage when soldering the IC and other semiconductors. Observe the
polarity of the electrolytic capacitor. Either a well-filtered dual 9-volt power
supply or 9-volt batteries may be used for the power source. Use a suitable metal
chassis to house the detector, with the meter and all controls on the front panel.
Fig. 2 - Leaf contact is made through a highly conductive metal
disc and electrode jelly of the same type used by physicians to make medical electronic
tests. Take care not to crush the leaf when making the contact, and use a stable
Connections to Plant. The pickup electrodes which are attached
to the plant (see Fig. 2) can be of almost any shape and any metal that has good
conductivity. Stainless steel or silver electrode pairs will work very well. Use
of dissimilar metals can cause undesirable electrolysis. The effective size of the
electrodes can be determined experimentally, but normally would be less than one
inch in diameter, If it is found that the leaf resistance is very high, a larger
diameter on the electrodes is required. If the plant has thin, moist, semi-opaque
leaves, a smaller electrode is used. Leaf conductance can be enhanced by using electrocardiographic
electrode contact cream, such as ECG KONTAX (Cat. No. 391, Birtcher Corp., Los Angeles,
CA 90032). It is water soluble and should be wiped off plant leaves after the experiment
is complete. Give the leaf a good rinse after that.
Connections to the electrodes are made through a shielded pair cable. The electrodes
are insulated from the metal clamp by pieces of plastic with the leaf gently compressed
between the electrodes. U sing the bridge resistor values shown in Fig. 1, the resistance
between the electrodes should not exceed 250,000 ohms. Also keep in mind that the
plant generates a small current of its own which, depending on the setting of switch
S2, is superimposed on the excitation current flowing in the circuit.
This phenomenon was discovered by Dr. L.J. Audus, of Bedford College, London,
in 1959, and reported by him in "Nature" in 1960. This report clearly showed that
plants are highly susceptible to electromagnetic fields.
In tests, a viable seed of any plant is inserted in a small plastic container
which is then placed between the poles of a strong magnet (of the magnetron type).
For control purposes, another similar seed and container are placed far away from
the magnet but with all other conditions being the same.
The "magnetized" seedling should show some bending effects plus a more emphatic
growth than the control specimen.
It is also possible to "quick-ripen" fruit with a 900-gauss magnet. For example,
a number of tomatoes placed at various distances around the magnet poles (anywhere
from 3 to 17 inches away) will show varying rates of ripening. Those closest to
the magnet will be the first to turn red. Horticulturists at the University of Utah
believe that the earth's magnetic field activates an enzyme system inside fruits
and vegetables causing them to ripen and that a similar thing is caused artificially
when the fruit is placed near a powerful magnet.
Theory of Circuit Design. The resistance of the plant leaf,
connected to BP1 and BP 2, forms part of a Wheatstone bridge with the other arms
formed by R1 and the two portions of R2. Power for the bridge is supplied by B1
controlled by R3. The final values of R1 and R2 are determined by the type of plant
leaf being used. The resistances must be increased when the leaf is thin and sensitive
to avoid over-excitation and undesirable side effects.
The input/output polarizer switch S2 permits reversal of the current applied
to the plant leaf since living matter tends to saturate and gradually cease to function
as an organic resistor.
The offset signal from the bridge is amplified in IC1, which is guarded by diodes
D1 and D2. When S3 is closed, these diodes limit the input voltage to the op amp
and protect it from large signals. However, once the circuit is operational and
maximum sensitivity is required after M1 has been nulled, S3 can be opened. The
output of the dc amplifier is indicated on a meter and can be used to drive a dc
pen recorder if a permanent record is desired. The output also drives an audio oscillator
(Q1 and Q2) whose frequency is a function of the dc signal. Transformer T1 couples
the audio tone to an optional audio tape recorder and to an internal speaker. Capacitor
C3 and resistor R16 provide feedback for the oscillator.
The circuit is sensitive to a few microamperes of input current, and when this
current changes as a result of plant stimulation, the bias on Q1 changes to alter
the pitch of the oscillator. Indicator lamp I1, momentarily activated by pushbutton
switch S7, permits intermittent tests of battery voltage and provides for the injection
of cue markers on a tape recorder since the pitch increases when S7 is activated.
Power to the audio oscillator is controlled by switch S5.
Transformer T1 provides an audio output for the tape recorder at all times regardless
of the position of S6. In one position of S6, R17 serves as a load; while in the
other position, R21, an 8-ohm pad, is the load. Volume control is essential since
the beep in the audio tone produced by S7 is annoying to listen to and can produce
an undesired stimulus to the plant.
While performing a particular experiment, the audio signal can be fed to one
channel of a conventional stereo tape recorder, while the other channel is supplied
with time markers (from WWV or CHU) or vocal announcements. This permits recording
of vocal stimulus to the plant as well as the plant's response.
Conducting Tests. In connecting the electrodes to the leaf,
apply just enough pressure to make a good contact with the leaf without crushing
it. Place the guard switch (S3) in the closed position to protect the IC from an
excessive input signal.
The prototype was constructed in sections on independent circuit
boards, but any other physical arrangement may be used as well as any type of cabinet.
When S1 is turned on, power is applied to the bridge circuit at a level determined
by R3, Then turn on S4 to activate the op amp IC. Potentiometer R2 is adjusted for
a meter null indication, This null may have to be readjusted when the plant is in
a non-stimulated condition. Note the pitch of the audio tone coming from the speaker
when the plant is quiescent. A change in pitch, as well as in the meter indication,
may result when the plant's well being is threatened.
In tests performed on a tree by the U. S. Department of Agriculture at the
University of California in 1964, the application of about 58 volts dc (negative
electrode high in the tree, positive attached to stainless steel nail driven in
the base of the trunk) showed that leaf density on the electrified branches increased
substantially after 28 days. Over a much longer period of time, the leaf growth
was 300% over that on the non-electrified branches.
It was also noticed that when a sensitive dc voltmeter was connected between
two conductors driven into a living branch (one at the center of a cut-off portion;
the other in the layer just under the bark), cutting twigs or branches in any other
part of the tree produced a sudden fluctuation on the meter. Even burning a leaf
produced a noticeable effect. Not only did the natural voltage rise and fall; at
times it even reversed polarity. There is no explanation for this effect.
The amount of excitation (via R3), and the state of the input/output polarizer
switch S2 must be determined by actual use. Obviously, the gain control (R8) can
be adjusted to obtain more or less sensitivity, and S3 can be opened to increase
the gain of the dc amplifier.
There is very little more to be said about the use of the response detector.
Patience and repetition are the key words. Obviously, also, controlled conditions
are a must. The area in which the plant lives must be quiet so that stimuli can
be applied. There should be a minimum of power-line noise to avoid fluctuations
in the audio and meter indications. There should be no r-f transmitters in the vicinity
to cause faulty indications.
The Backster Effect
Cleve Backster, one of this country's leading authorities on the polygraph
(lie detector) connected a pair of electrodes to a leaf of a dracaena massangeana
while it was being watered. Surprisingly, the plant's psychogalvanic reaction pattern
resembled that of a human subject exposed to emotional stimulation.
In further tests, Backster decided to ignite a match and burn the leaf to
which the electrodes were attached. At the instant that the thought image occurred
in his mind, a dramatic change appeared on the plant's polygraph readout. Tests
were carried out on other living matter including paramecium, fresh fruits and vegetables,
amoeba, mold cultures, scrapings from the roof of a human mouth, and yeast. All
showed similar results. It would appear that there is an unknown communication between
all living things, outside the orthodox electromagnetic spectrum. For example, placing
plants in lead-lined, Faraday-screened cages, fails to suppress the phenomenon.
It also appears that plants form some sort of emotional attachment to their
owners. Cleve Backster has reported that one plant responded to his emotional attitude
at a distance of over 1000 miles. Obviously, much work remains to be done in this
Electrophysiological Methods in Biological Research., J. Bures, Academic Press,
New York, 1967.
Plant Response as a Means of Physiological Investigations, J. C. Bose, Longmans,
Green & Co., London, 1924.
The Nervous Mechanism of Plants, J. C. Bose, Longmans, Green & Co., London,
Die Elektrophysiologie der Pflanzen, K. Stern, Springer, Heidelberg, 1924.
"Build a Psych-Analyzer." R. E. Devine, Popular Electronics, February 1969.
Plant Physiology, Second Edition, E. C. Miller, McGraw-Hill, New York, 1938.
"Electric Correlation between Living Cells in Cortex and Wood in the Douglass
Fir," E. J. Lund, Plant Physiology, 6:631-652, 1931.
"Proof of the Principle of Cell E.M.F.'s," H. F. Rosene, Plant Physiology, 10:209-224,
"Evidence of a Primary Perception in Plant Life," C. Backster, International
Journal of Para-psychology, 10:4, Winter 1968.
"Electronics and the Living Plant," L. G. Lawrence, Electronics World, October
"Experimental Electro-Culture," L. G. Lawrence, Popular Electronics, February
"Magnetotropism: A New Plant Growth Response," L. J. Audus, Nature, Jan. 16,
"Plants Are Only Human," W. McGraw, Argosy, June 1969.
"Electricity in Plants," B. I. H. Scott, Scientific American, October 1962.
Posted May 24, 2019