From semi-conductors to the rhythms of sensitive plants: The research of J. C. Bose

Abstract

J.C. Bose (1858-1937) was one of the world's first biophysicists. He was the first person to use a semi conducting crystal to detect radio waves, and the ingenious inventor of a portable apparatus for generating and detecting microwaves (~1 cm to 5 mm radio waves, frequency 12-60 GHz), as well as inventing many instruments now routinely used in microwave technology. Bose extended his specialist knowledge of the physics of electromagnetic radiation into insightful experiments on the life-processes of plants. He became a controversial figure in the west. He invented unique, delicate instruments for simultaneously measuring bioelectric potentials and for quantifying very small movements in plants. He worked with touch-sensitive plants, including Mimosa pudica, with plants that perform spontaneous movements, including the Indian telegraph plant Desmodium, and with plants and trees that did not make obvious rapid movements. Bose concluded that plants and animals have essentially the same fundamental physiological mechanisms. All plants co-ordinate their movements and responses to the environment through electrical signalling. All plants are sensitive explorers of their world, responding to it through a fundamental, pulsatile, motif involving coupled oscillations in electric potential, turgor pressure, contractility, and growth. His overall conclusion that plants have an electromechanical pulse, a nervous system, a form of intelligence, and are capable of remembering and learning, was not well received in its time. A hundred years later, concepts of plant intelligence, learning, and long-distance electrical signalling in plants have entered the mainstream literature.

Full text

FROM SEMI-CONDUCTORS TO THE RHYTHMS OF SENSITIVE PLANTS:
THE RESEARCH OF J.C. BOSE
V.A. SHEPHERD
Department of Biophysics, School of Physics, The University of NSW, NSW 2052, Sydney, Australia
Fax: +61 2 9385 4484; E-mail: vas@phys.unsw.edu.au
Received April 28, 2005; Accepted May 3, 2005; Published December 14, 2005
Abstract - J.C. Bose (1858-1937) was one of the world’s first biophysicists. He was the first person to use a semi conducting crystal to
detect radio waves, and the ingenious inventor of a portable apparatus for generating and detecting microwaves (~1 cm to 5 mm radio
waves, frequency 12-60 GHz), as well as inventing many instruments now routinely used in microwave technology. Bose extended his
specialist knowledge of the physics of electromagnetic radiation into insightful experiments on the life-processes of plants. He became
a controversial figure in the west. He invented unique, delicate instruments for simultaneously measuring bioelectric potentials and for
quantifying very small movements in plants. He worked with touch-sensitive plants, including Mimosa pudica, with plants that perform
spontaneous movements, including the Indian telegraph plant Desmodium, and with plants and trees that did not make obvious rapid
movements. Bose concluded that plants and animals have essentially the same fundamental physiological mechanisms. All plants co-
ordinate their movements and responses to the environment through electrical signalling. All plants are sensitive explorers of their world,
responding to it through a fundamental, pulsatile, motif involving coupled oscillations in electric potential, turgor pressure, contractility,
and growth. His overall conclusion that plants have an electromechanical pulse, a nervous system, a form of intelligence, and are capable
of remembering and learning, was not well received in its time. A hundred years later, concepts of plant intelligence, learning, and long-
distance electrical signalling in plants have entered the mainstream literature.
Key words: JC Bose, plant intelligence, sensitive plants, plant action potential, Desmodium, Mimosa, plant electrophysiology, Indian
science.....
INTRODUCTION
In Kolkata, India, there stands a statue amidst the
streams of beeping yellow and black taxis, rickshaws,
battered buses, carts, cows, goats and pedestrians. One of
the many kites that circle the skies sometimes lands and
rests upon its shoulder. The taxi driver, dexterously
squeezing between an oncoming bus and a rickshaw,
explains that this is Sir Jagadis Chandra Bose (1858-1937),
a legendary figure in India. J.C. Bose (Fig. 1) was one of
the first modern Indian scientists. His work spanned both
Western and Indian cultural and scientific traditions,
including physics, biology, botany, literature, teaching and
philosophy. His friend, the poet, novelist, short-story
writer, composer, painter, and Nobel Laureate
Rabindranath Tagore described him as "a poet in the world
of facts" (25). Since Bose did most of his work during the
hey-day of the British Raj, it is not surprising that the
legend that has grown up around him in India incorporates
elements of a "… lonely Indian David fighting a Goliathal
British establishment …the pitting of the colonised against
the coloniser" (19).
Whilst Bose’s turn-of-the-century work with semi-
conductors and microwave technology was at least 60
years ahead of its time, and is much respected today, his
biophysical plant research was less well received. Against
the tide of the times, Bose proposed that plants have a well-
developed nervous system. He argued that long-distance
electrical signalling is of major importance in plant
responses to the environment. He wrote many essays
advancing the view that plants are intelligent, capable of
learning from experience and modifying their behaviour
accordingly. He did not waver from the position that his
experiments proved the "..unity of physiological
mechanism in all life. For we find, in the plant and in the
animal, similar contractile movement in response to
stimulus, similar cell-to-cell propagation of pulsatile
movement, similar circulation of fluid by pumping action,
a similar nervous mechanism for the transmission of
excitation, and similar reflex movements at the distant
effectors" (13, p. 271). Poetically, he wrote, "…these trees
have a life like ours…they eat and grow…face poverty,
607
Cellular and Molecular Biology
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51, 607-619 ISSN 1165-158X
DOI 10.1170/T670 2005 Cell. Mol. Biol
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Abbreviations: PD: potential difference

sorrows and suffering. This poverty may…induce them to
steal and rob…they also help each other, develop
friendships, sacrifice their lives for their children…" (cited
in 39, p. 46).
Bose viewed animals and plants as not less than
human, but as part of a continuum of existence, which
included the inorganic world. He did not believe in a sharp
demarcation between the realms of living and non-living
(12). He argued that matter has life-like properties; "…how
can we draw a line of demarcation and say ‘here the
physical process ends and there the physiological begins?’
No such barrier exists…the responsive processes in life
have been foreshadowed in non-life …" (12) and ".... At
the source of both the inner and outer lives is the same
Mahashakti who powers the living and the non-living, the
atom and the universe" (Bose, cited in 39, p. 29).
Such a philosophical position was age-old in the East,
but stood in opposition to the mechanistic materialist
philosophy that underpinned much of Victorian science.
This opposition was later encapsulated in a famous debate
between Bertrand Russell and Alfred North Whitehead,
with Russell arguing, "life is matter-like" and Whitehead,
that "matter is life-like" (4). The Whiteheadian position is
argued today in the context of quantum physics and
neuroscience (56).
Bose did not believe in commercialisation, ownership
or patenting scientific ideas. These were symptomatic in
the West of the "…feverish rush…for exploiting
applications of knowledge, not so often for saving as for
destruction..…a mad rush, which must end in disaster"
(12). Instead, "…far more potent than competition [is]
mutual help and co-operation…" (12). Consequently, only
one of Bose’s numerous ingenious inventions was ever
608 V.A. Shepherd
Fig. 1 J.C. Bose at the Royal Institution, London, with his
radio equipment. The date is 1897, prior to his plant research.
patented; the "electric eye", or Detector for Electrical
Disturbances, a galena crystal semiconductor diode
detector, sensitive to microwave/millimetre and optical
waves (5,9).
During the inter-war years in Europe, Bose’s pacifist
and ethical views of science won the support of many
Western Nobel Laureates, including Einstein, Shaw,
Huxley, Romain Rolland, and Henri Bergson. Rolland
wrote to Bose in 1927 "…you have wrested from plants
and stones, the key to their enigma…you made us hear
their incessant monologue, that perpetual stream of soul,
which flows through all beings from the humblest to the to
highest" (cited in 39, p. 67). Bergson commented "…in
Darwin’s theory of natural selection…conflict is the main
theme; Jagadishchandra’s research…on the continuities
and on the beauties of consistency in nature and in life"
(cited in 39, p. 68). The great German plant physiologist
Gottlieb Haberlandt, who held a very different
interpretation of behaviour in the Mimosa (33, p 641)
commented "…We saw that there is a sleep of plants in the
true sense of the term…In Professor Bose there lives and
moves that ancient Indian spirit, which sees in every living
organism a perceptive being endowed with
sensitiveness…" (cited in 39, p. 68).
Between 1985 and 1900 Bose published ten papers in
the Proceedings of the Royal Society, all communicated by
Lord Rayleigh, and others in the "Philosophical
Magazine" and "The Electrician" (48). After winning the
admiration of physicists such as Rayleigh and J.J
Thompson, Bose crossed the border into plant biophysics,
research that occupied him until his death in 1937. He
immediately became a controversial figure in the west, and
by the late 1920’s, the world of plant researchers would be
polarised into "Bosephiles" and "Bosephobes" (19).
MILLIMETRE WAVES,
SEMICONDUCTING DIODES,
AND THE BIRTH OF RADIO SCIENCE
J.C. Bose’s research into the physics of electromagnetic
waves has been reviewed many times (6,24,37,44,48).
From 1894-1899 Bose proved himself an ingenious
inventor and physicist, a pioneer in the fields of semi-
conductor and microwave technology. The "electric eye",
patented in 1904, was the first solid-state semiconductor
diode detector. He invented instruments for generating and
detecting ~2.5 cm to 5 mm radio waves (microwaves) with
frequency 12-60 GHz. His portable "Hertzian wave
apparatus" was much admired at a time when European
scientists were working with large, "crude and clumsy
apparatus" (19). Bose was the first person to use a semi
conducting crystal to detect radio waves, and Emerson
quotes Sir Neville Mott, "…. he [Bose] had anticipated the
existence of p-type and n-type semi-conductors" (24).

Bioelectric rhythms in plants 609
Bose had studied physics, botany and physiology at
Christ’s College, the first Cambridge College to admit
Indians, and was much influenced by some of his teachers,
who included Lord Rayleigh. In 1884 he became a Junior
Professor of Physics at Presidency College, Kolkata, which
lacked research facilities, and where, as an Indian, he was
expected to accept a much-reduced salary. Converting a
tiny room adjoining a bathroom into a laboratory, he began
his now classic experiments into electromagnetic radiation
in 1894.
Bose invented and used numerous components of
microwave technology which are commonplace today,
including dielectric lenses, a horn antenna ("funnel"), wave
guides, and polarisers, some made from twisted jute fibres,
and even a Bradshaw’s Railway Timetable with tin foil in
between the pages (44). Many of these elegant instruments
are now preserved in the museum at the Bose Institute,
Kolkata. Bose investigated the quasi-optical properties of
millimetre waves, and experimented with diffraction,
refraction, and polarisation of electromagnetic radiation. In
1895, with prominent members of the British Raj in
attendance, he gave a dramatic public demonstration of
wireless signalling. He transmitted a pulse of radio waves
through a wall, received them with a "coherer", and set off
a relay, which fired a cannonball and a pistol, and exploded
some gunpowder (37). This demonstration preceded
Marconi’s famous Salisbury plain demonstration (4). The
work was presented at the Royal Institution in 1897, at the
invitation of Lord Rayleigh.
A turn-of-the-century scandal later erupted over who
had actually invented the "mercury coherer" (a semi
conducting diode) that Marconi used to receive the first
transatlantic wireless signal in 1901. Phillips analyses the
complicated history of the "mercury coherer with a
telephone", tracing it to Castelli, or Solari, of the Italian
Navy (42). However, Bondyopadhyay’s historical
detective work (4) traces the coherer to Bose’s 1899 paper;
"On a self-recovering coherer and the study of the cohering
action of different metals", published by the Royal Society
(8).
Bose’s work was years ahead of its time, and concepts
from his 1897 papers were recently incorporated into the
design of a 1.3 mm multibeam receiver, part of a 12 m
telescope at the National Radio Astronomy Observatory in
Tucson, Arizona (24).
THE BIOPHYSICS OF PLANTS
Bose regarded plants as intermediates between the
animals and the metals with which he had previously
worked. His plant research, from ~1900 until his death in
1937, was an extension of his earlier physical researches,
rather than a break from it. He performed hundreds of
intricate experiments using original and ingenious
apparatus designed by himself. His prolific output included
at least 13 books, numerous research papers and essays.
Only three of his books are considered here; "Researches
into the Irritability of Plants" (1913), "The Ascent of Sap"
(1923) and "The Nervous Mechanisms of Plants" (1926).
The books are written in a non-linear narrative style with
frequent cross-references, as if Bose was attempting to
paint a broader conceptual canvas than is possible in a
series of succinctly formatted research papers.
Bose sought to research three aspects of plant
responsiveness. These were i) "contractility" (movement
following a stimulus), ii) "conductivity" (transmission of
electrical excitation) and iii) "rhythmicity" (movements
taking place automatically, analogous to a heartbeat): (10,
p. 202). He carefully selected plant material in order to
compare and contrast these kinds of responses. The
Mimosa, or "touch-me-not" plant folds its leaflets and dips
the entire leaf as a response to being touched. In
Biophytum, Bose found that stimulus-induced and
spontaneous movements could take place in the same type
of plant, depending on the strength of the stimulus and the
history of the individual (10, p. 289). The Indian Telegraph
Plant Desmodium (Bon Charal or "forest churl") has a
trifoliate leaf, whose two small lateral leaflets make
mysterious spontaneous gyrations of regular period.
Finally, Bose measured spontaneous "pulsations", or
electro-mechanical oscillations, originating in cortical cells
of plants that did not make obvious stimulus-induced or
spontaneous movements. These included Chrysanthemum,
trees such as Ficus, Nauclea, the mango, monocotyledons
including the banana (Musa), palms, and "quiescent
vegetables" such as the tomato, carrot and potato.
Bose argued that these pulsations propelled the "ascent
of sap". Thus, "…the characteristics of the transmitted
impulse as ascertained from the mechanical response of
motile, sensitive plants find an exact parallel in the electric
response of ordinary non-motile plants. They are in fact
common to all plants…" (10, p. 103).
Bose viewed plants as individuals, and was careful to
note the condition and history of his experimental plants.
He did not "pool" his data and subject it to statistical
analysis. He stressed that constant environmental stimulus
and changeability was not the obfuscating nuisance it is
usually regarded as being in most plant physiological
experiments, but was essential for plant behaviour to show
itself; "…the continuance of normal functions depends on
external stimulus…deprivation of stimulus reduces plants
to an atonic condition in which all life-activities are
brought to a standstill…rhythmic activities are
maintained…by stimulus…" (13, p. 245). For example, he
showed that the velocity of the transmitted electrical
excitation in Mimosa depended on the tonic condition of
the plant. In "optimum" condition, the velocity was rapid,
and excessive stimulation resulted in fatiguing of the

response. However, in a "sub-tonic" plant, velocity was
low, and excessive stimulation enhanced the response. The
dependence on the strength and duration of previous
stimulations indicated a form of learning. "A plant
carefully protected under glass from outside shocks looks
sleek and flourishing, but its higher nervous function is
then found to be atrophied. But when a succession of blows
is rained on this effete and bloated specimen, the shocks
themselves create nervous channels and arouse anew the
deteriorated nature… " (12).
The velocity of electrical transmission was modified by
"…individual vigour…temperature, and by the season. In
summer, the velocity in thick petioles is 30 mm/sec, in
winter, as low as 5 mm/sec…" (14, p. 63). Even the age of
organs was important in determining the response; "…It is
impossible to dissociate from the consideration of the age
of a leaf its previous history as regards the stimulus of
sunlight…the uppermost or youngest leaf of Mimosa [is]
pre-optimum and less sensitive...the sensitiveness…
[reaches a] maximum as we descend lower...continuing to
descend...excitability [is] progressively decreased…" (10,
p. 267).
One might say that the standardised conditions of many
plant physiological experiments, with constant light period,
constant temperature, uniform watering, etc. are likely to
produce the effete and bloated specimens Bose deplored.
In addition, the usual process of statistical analysis will iron
out the individuality he regarded as so important.
MAJOR FINDINGS WITH MIMOSA
AND DESMODIUM
How could one measure leaf movements, especially in
relation to stimulation? Darwin had attempted to record the
gyrations of the Desmodium leaflets by plotting the
position of the leaf on a page, which resulted in a series of
near-circles. Bose designed the beautiful Resonant
Recorder, now in the Bose Institute Darjeeling (Fig. 2a).
This delicate device had frictionless jewelled bearings, and
a fine lightweight aluminium lever, which was connected
to the leaf, plus a vertical lever that wrote the response on
a smoked glass plate. This plate moved at a regular rate
using a clockwork mechanism. The problem of friction of
the writer against the smoked glass plate was solved by
having the writer vibrate or resonate, making intermittent
contacts with the plate (14, p. 55; 10, ch. 2). This was
achieved by periodic currents of exactly the same
frequency passed through an electromagnet. The
movements of the leaf could be recorded with a fine
precision (~1/100
th
of a second intervals)- "the record is
thus its own chronogram" (10, p. 22). The mechanical
response and electrical stimulus were coupled by having
the falling plate make electrical contact, which produced
the induction shock (Fig. 2b-2d).
Other extraordinary delicate instruments included the
High Magnification Crescograph, which could measure
tiny increments of growth in intervals of a second, under
normal conditions or with chemical or electrical
stimulation, the Electric Probe (Fig. 3a-3d), an early
intracellular microelectrode, whose tip was in circuit with
a sensitive galvanometer and could be driven into tissue in
0.1 mm increments, and microelectrodes, which were
connected to various parts of a plant with saline kaolin
paste. Different intensities of electrical stimulation were
produced with an induction coil, with a primary and
secondary coil and a slide (potentiometer) that could move
them precisely together or further apart, generating
currents of "feeble" (0.5-8 µA) to strong (100 µA).
Currents were measured with a "microamperemetre", and
Biophytum responded to a "feeble" stimulating current of
about 0.5 µA (10, p. 27), which was too feeble for his own
tongue to detect (13). In fact, the " sensitiveness of Mimosa
to electrical stimulation is high and may exceed that of a
human subject " (10, p. 51).
With his numerous experimental set-ups, Bose was able
to simultaneously.
1. Measure plant movements and electric potentials.
2. Measure very small electrical oscillations.
3. Apply mechanical stimuli such as touch, pricking,
cutting.
4. Apply electrical stimuli, such as induction shock,
constant current, make or break of positive or negative
current.
5. Vary hydrostatic pressure using a U-tube, or vary
osmotic pressure (using solutions such as KNO
3
…).
6. Apply chemical inhibitors or poisons (KCN, HCl, NH
4
,
H
2
S, NO
2
, SO
2
, anesthetics such as chloroform and ether).
7. Suddenly change the temperature with an electrically
regulated thermal chamber, chilled water, heating a probe.
8. Vary light conditions.
9. Measure tiny growth increments over very short time
intervals.
Bose’s main conclusions were radical. He argued that
plants, like animals, have a well-defined nervous system.
Plants also have receptors for stimuli, conductors
(nerves), which electrically code and propagate the
stimulus, and effectors, or terminal motor organs. The
"...physiological mechanism of the plant is identical with
that of the animal"…(14, p. ix). "…All plants and their
organs are excitable, the state of excitation being
manifested by an electric response of galvanometric
negativity (relative depolarization)" (14, p. 95). "It can only
be in virtue of a system of nerves that the plant constitutes
a single organised whole, each of whose parts is affected by
every influence that falls on any other" (10, p. 121).
The motor organ in both Desmodium and Mimosa was
the pulvinus, a joint-like thickening at the base of a petiole,
which supports the leaf (or petiolule, supporting a leaflet).
610 V.A. Shepherd

Bioelectric rhythms in plants 611
b
c
d
a
Fig. 2 Some of Bose’s equipment and some measurements he made with it. a) The Resonant Recorder (reproduced from Fig. 4, 10). This
device had "frictionless" jewelled bearings, a fine lightweight horizontal lever connected to the pulvinus or leaf, and a vertical lever for writing
the response on a smoked glass plate, which moved at a uniform rate using a clockwork mechanism. In this configuration, the duration of an
"induction shock" applied to Mimosa was determined by a metronome, which completed the electric circuit. The illustration shows a Mimosa
plant ready for measurement of leaf movements. b) The record shows the leaf-dropping response in Mimosa made with the Resonant Recorder
(reproduced from Fig. 14, 10). Dots are at 1/10 sec. intervals during the "contractile" or leaf-dropping phase and at 10 sec. intervals during
recovery. Vertical marks, 1 min. intervals. c) The rhythmic gyrations of the leaflets of the telegraph plant Desmodium [reproduced from Fig.
145 in (10)]. Individual dots are 2 sec. apart. This leaf was measured in summer and the whole period is about a minute, although in winter this
increased to 4-5 min. d) Arrest of spontaneous movements in Desmodium by a cut applied at the first arrow. The pulsatile movement was
revived by an electric shock at the second arrow. An electrical stimulus could substitute for a mechanical one. [reproduced from Fig. 145 in
(10)].
The fall or rise of the leaves indicated changes of turgor
pressure in the pulvinus. The upper portion was less
excitable than the lower. In Mimosa, the excitatory
response could be induced by touch, sudden temperature
change, by initiation or cessation of a constant current and
by induction shock. Crucially, the mechanical (touch)
stimulus could be substituted for by an electrical one. Bose
concluded that electrical signals (including action
potentials) controlled the leaf movements. The excitation
was bipolar, moving both with and against the direction of
the transpiration stream. A non-electrical stimulus (light)
applied to the upper half of the leaf produced either of two
responses- an increase of turgor (and leaf lifting) with
moderate or short-lived stimulus, or an abrupt leaf-
dropping response (loss of turgor on the lower half) with a
strong stimulus.
The former response was associated with turgor
increase, expansion of cells, and "galvanometric positivity"
[relative hyperpolarisation], whilst the latter was a true
excitation, a wave of "galvanometric negativity" [relative
depolarisation], associated with contraction and reduction
of turgor pressure.

Bose concluded that the plant nervous system is
complex, with both sensory and motor components.
Electrical propagation depended on living cells.
The major conduction pathway or nerve, (established
with the Electric Probe), was the phloem. Staining with
safranin and haemotoxylin showed that there were two
phloem bundles, one internal and one external to the xylem
(14, p. 34). There was a marked difference in the velocities
of excitations moving through them. Bose considered them
the equivalent of sensory and motor nerves in the animal.
The inner phloem conducted the fast motor impulse, and
the outer, the slower sensory impulse (14, p. 189).
A unilateral stimulus was conducted only on the
stimulated side, but if repeated, or if the stimulus applied to
a sub-petiole was increased to a critical intensity, the slow
sensory impulse was converted to a fast motor impulse in
the pulvinus. The ascending impulse was then converted
into a descending "true" excitation after crossing over at the
apex of the stem (14, p. 42, p. 204). Stimulating the stem
produced an electrical signal propagated to the leaves.
Stimulating the leaves produced an electrical signal
propagated to the stem, and then conducted both up and
down, causing other leaves to collapse (14, p. 40).
Bose suggested that there was a "synapse" between the
pulvinus and the stem. The signal was propagated
preferentially from stem to pulvinus, and moderate
stimulation of the pulvinus alone was not accompanied by
collapse of the leaves (13, p. 44). "The typical
experiments…prove that conduction is irreciprocal. They
also indicate the existence of a synapsoidal membrane,
which by their valve-like action, permit propagation [small
to moderate stimulus] in one direction only" (14, p. 48).
The electric signal was a propagated protoplasmic
excitation, as in the nerve of an animal (14, p. 20). Signal
transmission was arrested by a blocking constant current
(two electrodes placed 5 mm apart in between the pulvinus
and the point of stimulation, with a constant current
maintained between them; 14, p. 29). In "…the contractile
cells of the pulvinus…a wave of excitatory contraction
passes from cell-to-cell at a rate slower than the nervous
impulse. I distinguished this as cellular propagation of
excitation". The phenomenon is not unlike the propagation
of a wave of contraction from cell-to-cell in the muscles of
the animal heart (10, p. 91).
Bose applied similar methods to the spontaneous leaf-
movements in Desmodium. In winter, the period of the
movements was ~four min - in summer, this increased to 1
min. The gyrations of the Desmodium leaflet were due to
rhythmic alternations between "galvanometric
negativity"[relative depolarisation] and "galvanometric
positivity" [relative hyperpolarisation] of pulvinar cell
electric potential. These electrical oscillations or
"pulsations" were of identical period to the changes in cell
turgor pressure. "Galvanometric negativity" was coupled
with turgor decrease, and leaf downstroke, and
"galvanometric positivity" with turgor increase and leaf
upstroke.
The pulsations were strongly temperature-dependent
"…alternately rendered active or inactive above and below
the critical temperature" (13, p. 69), influenced by light-
levels, depressed or arrested if turgor pressure was reduced,
inhibited by strong or repeated stimulus, arrested by large
doses of anesthetic or poisons. Repeated stimuli meant
fatiguing and loss of response. Interestingly, the pulsations
were arrested by "short-length Hertzian waves"; radio
waves, possibly microwaves (13, p. 106).
The excitatory response in Mimosa, and rhythmic leaf
movements in Desmodium were both blocked by KCN,
CuSO
4
, sudden application of ice water and chloroform.
Just as strong electric stimulus of the pulvinus made
Mimosa leaves dip, without mechanical stimulation, a cut
in the Desmodium stalk prevented the rhythmic leaf
movements, but these were restored by an electric current
passing through the pulvinus (Fig. 2d, 10).
Overall, leaf downstroke in Desmodium was due to
"diminution of turgor, contraction, diminished growth rate,
negative mechanical response [leaf dropping], electric
response of galvanometric negativity [relative
depolarisation]". Leaf upstroke was due to "increase in
turgor, expansion, increased growth rate, positive
mechanical response [leaf lifting], electric response of
galvanometric positivity [relative hyperpolarisation].
From these results, Bose (10, p. 94) generalised that all
forms of significant direct stimulation produced a decrease
in turgor pressure, a contraction of cells, a transient
diminution of growth rate, a negative mechanical response
(such as dropping of leaves) and a "galvanometric
negativity" [relative depolarisation]. Feeble stimuli, on the
other hand, produced directly opposite effects, such as an
increase of turgor, expansion of cells, transient increase in
growth rate (his High Magnification Cresco graph showed
that growth in Desmodium was pulsatile, with alternating
spurts, and that this corresponded to the patterns of
electrical activity), and a "galvanometric positivity"
[relative hyperpolarisation].
Strong stimulation (of leaf or stem) in Mimosa induced
a wave of protoplasmic, electrotonic excitation
(depolarisation), which was transmitted through the
phloem parenchyma to the pulvinus, and there it induced a
decrease of turgor and subsequent fall of the leaves. In
Desmodium, stimulation of the pulvinus by light brought
about the rhythmic movements, through alternate
contraction and expansion (turgor pressure changes) of the
pulvinar cells, associated with a regular electrical
"pulsation" or oscillation.
Bose viewed the expansive phase as hydraulic, and the
contractile, depolarising phase as nervous and electrical, a
true excitation. The two were antagonistic (13, p. 255).
612 V.A. Shepherd

Thus there were two forms of signalling, one essentially
hydro-mechanical, the other a true, propagated excitation,
and the first could be converted into the second by a strong
enough stimulus.
Bose concluded that all plants have a pulse.
The tension-cohesion hypothesis proposed by Dixon and
Joly in 1894 remains the most widely accepted theory of
the "ascent of sap". Bose found it inconceivable. The
columns of water in the xylem could not sustain the
necessary tensile strength, when, surely, air-bubbles would
form and impair the cohesion (13, p. 2). Instead, he
believed that the ascent of sap depended on the activities of
living, pulsating cells. All plants, including trees, had a kind
of pulse, a rhythmic electrical oscillation accompanied by
turgor increase and decrease.
Using the Electric Probe, Bose found "pulsating" cortical
cells abutting the endodermis (13, p. 219). He found
"periodic mechanical pulsations corresponding to electric
Bioelectric rhythms in plants 613
Fig. 3 a) The Electric Probe [reproduced from Fig. 75 in (13)]. The tip of the Probe was in circuit with either a sensitive or Einthoven
galvanometer, and the device could be driven, by small (0.1 mm) increments into the tissue by turning the screw. Bose achieved remarkable
precision of measurement – a deflection of 1 mm PD between electrodes was equivalent to a 1 mV deflection of the galvanometer. In some
cases, he measured potentials as small as 0.1 mV. The tip of the probe enters at A, and a reference contact is made with a distant or dead leaf.
The micrometric screw enables the probe to be gradually introduced. b) Asection of a Brassica petiole showing the relative cellular activity in
terms of electromechanical pulsations. The pulsations occur mainly in the inner cortical layer abutting the endodermis. [reproduced from Fig.
77 in (13)]. c) Periodic groupings of the electrical oscillations in the pulvinus of Desmodium [reproduced from Fig. 69 in (13)], which
accompanied the mechanical oscillations of leaflet position shown in Fig. 2c. d) Regular electromechanical pulsations in the cortical cells of
Musa, the banana. Bose used an Einthoven galvanometer to measure the amplitude of these pulsations in Nauclea as ~0.4 mV, and lasting
~13.5 sec. [reproduced from Fig. 71 in (13)].
a
c
d
b

pulsations, as in Desmodium" (13, p. 214). These
pulsations were recorded on a photographic plate driven by
clockwork, resulting in a "galvanograph" (Fig. 3c, 3d). The
"galvanonegative" part of the pulsation was associated
with contraction of the cells and a loss of turgor and the
"galvanopositive" part with the expansion and swelling of
these cells. As with Desmodium, periodic mechanical
pulsations, swelling and contracting, were directly coupled
with periodic electrical "pulsations". Fluid was injected
into the xylem by expulsive contraction of these cells in the
cortex. The xylem was merely a reservoir from which
water could be withdrawn or injected according to the
conditions, time of day, and temperature (13, p. 222). In a
series of extraordinary experiments, Bose connected the
Electric Probe (and reference electrode) to trees as tall as 30
m. (the mango, and the Cadamba, Nauclea), wiring the
signals to a sensitive galvanometer in the lab. He used an
Einthoven galvanometer to measure the magnitude of the
electric oscillations, and found they were about 0.4 to
several mV in amplitude in Nauclea. The pulsing rate
changed from 13.5 sec for a complete pulsation to 3 min.,
with increasing temperature (13, p. 214). The pulsations
were feeble on cold mornings, maximal at noon, and
changed in amplitude during the course of a day.
If all the cells pulsed together at the same time, there
could be no injection of fluid into the xylem. Bose
reasoned that there had to be a phase difference of
pulsations along the length of the stem. In other words, the
pulsations were a sort of peristalsis. By making a
permanent electric contact with a stem, and bringing the
Electric probe progressively closer to it, Bose found a
critical distance at which the potential difference between
electrodes was maximal and another critical point where
no potential difference (P.D) existed. He reasoned that the
distance at which the maximum P.D was found
corresponded to half the pulse width. The pulse width was
found to be 100 mm in Chrysanthemum, 50 mm in banana,
and 40 mm in Canna (13, p. 225).
He measured similar pulsations in field-grown tomato,
vines, and potatoes. The pulse width increased with sudden
irrigation, when warm water was applied to the banana
plant, and changed with passage of a constant electric
current. The pulsations were enhanced by increased
hydrostatic pressure, moderate constant current and
increased temperature. They were arrested by a large dose
of chloroform (which also arrested the ascent of sap),
plasmolysis of the roots, a large drop in temperature, and
poisons such as KCN.
In fact, it seemed that "…any agent affecting the
pulsations induced corresponding effects in the ascent of
sap…" (13, p. 258). A succession of periodic hydraulic
waves, propagated waves of contraction preceded by
waves of expansion, squeezed the sap upwards. The
velocity of the ascent of sap was caused by a propagated
hydraulic wave of contraction preceded by expansion,
squeezing the sap forward.
Bose argued that all plants used a universal mechanism
involving coupled electrical and mechanical oscillations,
protoplasmic contraction and expansion.
He summarised his results, " …expulsion of sap by cells
of the pulvinus on stimulation is an essential part of its
motile mechanism, and this applies also to the pulvinule of
the leaflet of Desmodium in its ‘spontaneous
oscillation’…evidence has been accumulated…. that the
active expulsion of sap by living cells is an essential part,
not only of the mechanisms of movement, but also ...for the
distribution of fluid throughout the plant…" (13, p. 144).
He compared a tree to a bar magnet, with two poles at root
and shoot, and an apparently neutral region in between. As
the two parts of a divided bar magnet both then show a
north and south pole, so it was with the plant, all the way
down to the individual pulsating cell. All cells pulsed, and
each "must exhibit polarity, [one] end absorbing water, [the
other] end excreting it" (13, p. 192).
Furthermore, the polar plant could be divided into
quadrants, so that its movements were not only up and
down, but also clockwise and anticlockwise. He invented a
"torsional recorder" to investigate heliotropic movements,
and found that the motor organ had four effectors, one for
each of these directions. Plants were exquisitely sensitive
to light and temperature, and " a beam of light falling on the
left flank of the pulvinus of Mimosa induces an
anticlockwise torsion [and vice-versa]" (14, p. 156). Light
applied to one side of the stem caused turgor to increase at
the diametrically opposite point (14, p. 165). Heliotropic
movements in the sunflower Helianthus, where the entire
petiole was the motor organ, were due to the interplay
between contraction and expansion of each side of the
plant in relation to the direction of light. In terms of a leaf,
"…the leaf is...thus adjusted in space by the co-ordinated
action of four reflexes, equilibrium being attained when the
leaf is perpendicular to the incident light" (14, p. 172).
BOSE’S WORK IN TODAY’S CONTEXT
Electrical signalling in plants
In 1937, at the time of Bose’s death, and afterwards,
electrical signalling in plants had become a topic of minor
interest, or even an untouchable one. The discovery of the
growth regulator auxin led to intense research on plant
growth regulators, and to the idea that plant signalling took
place predominantly by chemical diffusion. Since plants
did not move rapidly, had no eyes, ears, or obvious brain,
since they were simple automata stuck in the ground, why
would they need a nervous system? Factors other than the
discovery of auxin contributed, and these included the use
of plants in parapsychology, institutional nationalism,
racism and sexism (61). Publication of a best-selling
614 V.A. Shepherd

popular book "The Secret Life of Plants" in 1973, critiqued
by Galston and Slayman (30), apparently made research
into plant electrical signals "...untouchable in the eyes and
minds of funding agencies" (22). This book included a
chapter on Bose’s research, which Galston and Slayman
viewed favorably. However, it mainly focussed on the
work of a discredited lie-detector expert, and apparently
fostered unscientific beliefs about emotional
communication between plants and humans (30).
Nonetheless some determined plant scientists, in the
70s and 80s, continued to argue that action potentials are
the multi-functional signals responsible for co-
coordinating plant responses to the environment
(20,21,43). Nearly a century after Bose’s original work,
Wildon et al. (62) demonstrated that proteinase inhibitor
genes were activated in distant tissues following a flame
wound, and this was brought about, not by a chemical
signal, but electrically. The actual electrical signal was a
variation potential (an electrical variation in living cells due
to a hydraulic surge or chemicals) rather than an action
potential (22). In addition to playing a role in respiration,
transcription, and translation, a flame-induced electrical
signal was recently (in 2004) shown to transiently halt
photosynthesis in Mimosa pudica (see 22).
What of the two nervous systems, sensory and motor,
that had Bose proposed? There are at least two kinds of
electrical signal, the "variation potential" as compared with
the action potential (43). The variation potential, a small
depolarisation, is not evoked electrically, and is graded
according to stimulus intensity. It is probably brought about
by mechanosensory and/or ligand activated ion channels
responding to a hydraulic surge or chemicals in the non-
living xylem (22), rather than in the phloem (as Bose had
suggested). Similarly, the receptor potential in giant
characean cells is a small depolarisation brought about by
mechanosensory ion channels, and occurs in response to
touch stimulus (53). It is graded according to stimulus
intensity, and does not travel from cell-to-cell. However,
when a critical depolarisation threshold is reached, the
receptor potential initiates an action potential, which does
travel intercellularly. Reduction of turgor pressure alters the
magnitude of the receptor potential for a given stimulus,
but not the threshold for the action potential (52). We have
compared the touch response to the turgor-regulating
response in salt-tolerant characean cells, where an initial
depolarisation, due to mechanosensory channels, is
transformed into an electrical signal, essential a long, slow
action potential (51). Whether these two types of system,
mechanosensory versus excitatory, are indeed antagonistic,
in the fundamental sense that Bose meant, is unknown.
Many of Bose’s findings were confirmed by later
researchers (50). Stimuli such as chilling, heating, cutting,
touching, electric stimulus, changes in quality or quantity
of light, or external osmolarity can result in action
potentials, which are electrotonically transmitted at rates of
at least 10-40 mm s
–1
(61). A plant action potential is now
interpreted as a sudden depolarisation, where, briefly, a
stimulus releases Ca
2+
to the cytoplasm, activating Cl
–
channels and voltage-dependent K
+
channels, resulting in
efflux of Cl
–
and K
+
(40, 61), water efflux, loss of turgor
(63) and a transitory contraction of the cell, as measured by
laser interferometry in single characean cells (41). These
patterns of Ca
2+
influx, K
+
and Cl
–
efflux, contraction and
turgor change are fundamental motifs intrinsic to the
"osmotic machinery" enabling plant movements (34).
A shift in attitude, from that espousing that plants use
predominantly chemical signals to one emphasising
electrical signals, is discussed by Roberts (45).
An enormous literature is devoted to Mimosa pudica.
The classic papers of Fromm and Eschrich, in 1998
(27,28,29), demonstrate that excitation does indeed travel
in the phloem, and that the turgor decrease in the pulvinus
is associated with depolarisation and expulsion of Cl
–
and
K
+
as well as a sudden unloading of sucrose from the
phloem (27). The contractile actin-myosin system is indeed
involved in the collapse of the leaves, and in the
"spontaneous" movements of Desmodium (reviewed, 60).
Motor cell movements in Mimosa are inhibited by drugs
that affect the acto-myosin system involved in cytoplasmic
streaming in plants, and in muscle contraction. The
contraction in Mimosa is similar in many ways to muscle
contraction (54).
In the 1990’s, the elegant experiments of Antkowiak et
al. and Antkowiak and Engelmann (1,2) show that the
gyration of the Desmodium leaflets is indeed caused by
rhythmic changes in the turgor pressure of pulvinar cells,
which are directly coupled with rhythmic oscillations of
membrane potential differences (1). Using ion-sensitive H
+
and K
+
extracellular microelectrodes as well as
intracellular microelectrodes, they showed that the "down"
stroke of the leaflet occurred when the pulvinar motor cells
were relatively depolarised, apoplastic (extracellular) K
+
concentration was high, the external PD was negative. The
cells contracted, losing turgor. By contrast, the upstroke
occurred when the motor cells were hyperpolarised,
apoplastic K
+
concentration declined, the external potential
difference (PD) was positive, the cell expanded, and turgor
pressure increased (1,2). Like Bose, Antkowiak et al. (2)
found that increased temperature shortened the period of
the oscillations, and an anesthetic (enflurane) abolished the
movements (1). Pulsed radio-frequency fields do
transiently alter the amplitude, period and phase of the
leaflet rhythms in Desmodium (23).
Plant pulsations
According to Nandy (39), Bose’s theory of the ascent of
sap, which depended on the electro-mechanical
"pulsations" of living cells, embarrassed his colleagues
Bioelectric rhythms in plants 615

after his death, because the Dixon-Joly model had by then
been completely accepted. What is to be said now of these
intrinsic electro-mechanical pulsations, which Bose
viewed as an endogenous mode of cellular
communication?
Gensler and Diaz-Munoz, and Gensler and Yan (31,32)
used a similar experimental set-up in the 1980’s, and found
similar electrical "pulsations". With a palladium electrode
inserted in the stem, and a reference palladium electrode in
the root zone of tomato plants, they measured a stable,
reproducible large potential difference (~-400 mV), and
recorded characteristic potential/time fluctuations, which
they called "electrophytograms" (32).
The form of these "pulsations" was directly related to
the condition of the plant, its water status, and atmospheric
changes. These phytograms strongly resemble Bose’s
"galvanographs", and the method has now been
commercialised, as a device to aid farmers. The
"pulsations" do seem to be directly related to "the ascent of
sap". Inserting an electrode in the stem, and a reference
electrode in the root zone of cotton plants, these researchers
simultaneously measured apoplastic electropotentials and
stem diameter before and after rainfall and irrigation.
Stems contracted during the day and expanded at night,
coupled with a decrease and increase of electropotential.
Following irrigation stems expanded and the
electropotential immediately dropped.
In 2001, Minorsky (36) discussed whether small
amplitude low frequency (~0.1 to 0.25 mV, 0.1 to 10 Hz)
oscillations measured in plants are related to geomagnetic
pulsations, with trees acting as antennae. The small
amplitude, slow "pulsations" Bose measured, which were
affected by time of day, might fall into this category.
At any rate, the rhythmic changes in cell volume,
brought about by influx and efflux of water, and coupled
with the rhythmic changes in cell electric potential
difference in Desmodium, have been confirmed by many
researchers. Mitsuno and Sibaoko (38) found that the
pulsations were arrested by inhibition of oxidative
phosphorylation, as Bose had found, and by vanadate,
which suggested that an electrogenic ion pump
rhythmically alters its activity. They also describe the
torsion Bose had measured. Electric oscillations are
coupled to growth oscillations (or "pulses") in roots (55). In
roots, oscillatory patterns of H
+
, K
+
, Ca
2+
and Cl
–
uptake
were measured using a non-invasive ion flux measurement
technique (49). This was the first report of ultradian
oscillations in nutrient acquisition, and these authors
suggested that the H
+
-translocating ATP-ase must operate
rhythmically.
Are the "pulsations" indeed associated with "the ascent
of sap"? An alternative to the widely accepted Dixon-Joly
theory was proposed by Canny at the end of the 90s
(16,17,18). In his Compensating Pressure theory, living
cells provide "compensating pressure", which refills the
xylem when the water columns cavitate early in the day. In
this theory, the classical measurements of large tensions in
the xylem are instead measurements of the compensating
pressure, which is matched to increasing rates of
transpiration and of embolism. Hydrolysis of starch to
sugar in living cells increases osmotic pressure, providing
a "squeeze" which refills the embolising vessels when
necessary. The endodermis in the roots acts as "pump", a
one-way valve and a barrier containing the pressure, due to
the small size (~5 nm) of pores traversing it. The
Compensating Pressure Theory has sparked intense debate
over the last decade.
In Canny’s words "...the xylem is not a vulnerable
pipeline on the edges of disaster exerting large forces on
strong threads of metastable water liable to breakage. It is
a self-sustaining pipeline that controls the flow of weak
water under varying evaporative demands using at least
five levels of homeostatic response and adjustment… (18,
p. 907). This is "...an ultrastable system…not just a
homeostat, but one that responds to environmental changes
outside its previous operating experience by changing the
parameters of its operation and regaining stability" (18, p.
907). Bose’s model, whilst rather different, also envisaged
the "ascent of sap" as an ultrastable, adaptable system.
Plant intelligence and learning
In his long, comprehensive and thoughtful review,
Trewavas, in 2003 (59), points out how biased is the usual
concept of intelligence, where behaviour is usually
associated with the rapid movements made by animals.
Applying the definition of intelligence from D. Stenhouse
("adaptively variable behaviour during the lifetime of an
individual"), Trewavas gives numerous examples of
intelligent behaviour involving growth and development in
plants. These include roots navigating the maze of the soil,
constructing a perspective of local space and adjusting
growth patterns accordingly. Furthermore, plants actively
forage, using strategies similar to those used by foraging
animals. Plants can learn through trial and error, which
requires having goals, assessing and modifying growth
behaviour. A kind of memory enables plants to anticipate
difficulties, and to grow around them. Plant behaviour is
intentional.
How is it possible for plants, which lack an obvious
brain and the capacity for rapid movement, to foresee,
remember, plan and respond? In 2005, the view is that
calcium signalling, involving electrical signals, underlies
plant responsiveness (15). This involves chemical
signalling also, for it seems that calcium is either an agonist
or antagonist of all plant growth regulators, including auxin
(26).
The "chemical diffusion" concept of plant signalling,
based on the discovery of auxin, dominated plant
616 V.A. Shepherd

physiology for many years, whilst the electrical signalling
concept fell by the wayside. Thus, it is interesting and
ironic that a recent paper (3) argues that polar auxin
transport is brought about by vesicle trafficking, via proton
gradients generated by vacuolar/vesicular ATP-ases. In
other words, according to these authors, polar auxin
transport has much in common with synaptic signal
transmission in excitable animal tissues. "Higher plants
show neuronal-like features in that the end-poles of
elongating plant cells resemble chemical synapses" (3).
Recalling Ashby’s Law of Requisite Variety, how is it
possible for a mere divalent ion to control so many
processes that are far more complex? Trewavas (57,58) has
proposed a neural net concept of Ca
2+
signalling, as the
basis of plant learning and intelligence. He concludes that
the electrical signalling systems [e.g. action potentials] of
plants have the potential for computation and learning.
Changes in cytoplasmic Ca
2+
are the basis of the intelligent
system, not through Ca
2+
diffusion, but through propagated
waves of Ca
2+
release. Plant cells can compute, remember
and learn, through a Ca
2+
-based neural net system
(7,57,58).
Calcium channels, located in plasma membrane,
vacuolar and endoplasmic reticulum membranes, are
envisaged as a network. Signals initiate the IP
3
cascade and
Ca
2+
channels open only when both IP
3
and Ca
2+
bind. The
released Ca
2+
opens further channels, in a "Mexican
wave", and can associate with Ca
2+
-binding proteins. The
Ca
2+
waves are spatially structured, and the IP
3
- sensitive
channels make for a "coincidence counter". Only specific
directions are propagated whilst others are inhibited.
Stimulus induces Ca
2+
oscillations in plant cells (35).
Calcium oscillations reflect co-operative integration of the
behaviour of many IP
3
-sensitive channels, and each Ca
2+
channel or cluster of channels is the equivalent of a node in
a neural network.
Each is a "switch" which can direct the flow of
information, block or pass signals that arrive at the same
time, and behave as an AND/OR logic gate. Trewavas
argues that this Ca
2+
-based neural net is a means for
computing, remembering and learning that is unique to
plants. It accelerates information transfer and it can be
reinforced. Repeated signals make the path more sensitive
whilst too many signals inhibit it. A similar Ca
2+
signal can
have different effects in different cells, which can
remember previous experience, and know where, and
what, they are.
WHY WAS BOSE NOT TAKEN SERIOUSLY
IN HIS TIME?
Bose’s work was treated with doubt and suspicion in his
day. The failure to accept his Mimosa experiments as valid
held up research into plant electrical signalling for many
years (54). One wonders why this was the case. In 1901,
Bose lectured at the Royal Institution and the Royal
Society, where he argued "…every plant, and even the
organ of every plant, is excitable and responds to stimulus
by electric response…" (10). He drew analogies between
semi-conducting electric responses in semi conducting
metals, plants and muscles. In the audience were
prominent electrophysiologists of the time, Sir John
Burdon-Sanderson and Auguste Waller, who were to
become powerful professional enemies of Bose.
According to Dasgupta (19), Burdon-Sanderson
objected to the use of the word "response" in connection
with metals, and insisted that ordinary plants did not have
electrically mediated responses. These were restricted to
exceptional and strange insectivorous plants, such as the
Venus Flytrap, in which Burdon-Sanderson had discovered
the plant action potential. Waller said nothing, but a few
months later published his own paper on electrical
behaviour in ordinary plants, and claimed priority for the
discovery of "vegetable electricity". This led to a long-
standing enmity between Bose and Waller, which has been
reviewed in depth (19).
Burdon-Sanderson later scathingly reviewed and
recommended rejection of a Mimosa paper submitted by
Bose to the Proceedings of the Royal Society. Paul Simons,
describing the incident, writes, "Why he was so
antagonistic amazes me. Was it professional jealousy
because he himself had not investigated the Mimosa?" Was
it because Bose did not cite Burdon-Sanderson’s paper on
the Venus Flytrap? Simons (54) writes that doubt was
probably cast on Bose’s professional competence. He was
controversial, he had said that there was no demarcation
between life and non-life (had he said that metals are
alive?), and furthermore the Victorian science
establishment in England could not stomach mavericks.
There is another possible reason. Burdon-Sanderson’s
pioneering 1873 and later papers on trap closure in the
Venus Flytrap are still cited today, but Burdon-Sanderson
was predominantly a medical physiologist, who devoted a
large part of his life to "making medicine scientific"
through animal experimentation (46). Charles Darwin
wrote to him, on 15/8/1873, that it would be worthwhile to
look for electrical changes in the leaves of insectivorous
plants. A month later Darwin expressed his pleasure that
Burdon-Sanderson had discovered the electrical
phenomena associated with trap closure.
The lively correspondence between the two was
concerned with the mechanism of digestion in
insectivorous plants (was it like a stomach? It was), until,
in 1873, not long after the Venus Flytrap work was
published, the letters suddenly focussed on the activities of
"anti-vivisectionists" and a looming Vivisection Bill. Both
Burdon-Sanderson and Waller had run-ins with what
would today be called "animal rights activists". Burdon-
Bioelectric rhythms in plants 617

Sanderson’s "Handbook for the Physiological
Laboratory", published in the same year as the Venus
Flytrap work, described procedures for operating on
animals with no mention of using an anesthetic.
The book might have contributed to the passing of the
"Cruelty to Animals Act" in England in 1876, which
compelled researchers to use anesthetics in animal
experimentation. We can only imagine the effect J.C. Bose
must have had, when he claimed that plants, like animals,
had nervous systems, and furthermore, expressed views
such as "…. the complex mechanism of the animal
machine that has long baffled us, need not remain
inscrutable for all time, since the intricate problems of
animal life would naturally find their solution in the
simpler vegetable life" (11). This would mean "very great
advance in the sciences of general physiology, of
Agriculture, of medicine and even of psychology" (11).
To Bose, the problem was more easily understood. "I
had unwittingly strayed into the domain of a new and
unfamiliar caste system, and so offended its etiquette…"
(12).
CONCLUSION
A hundred years ago, J.C. Bose demonstrated the
fundamental importance of electrical signalling in plants,
and measured electro-mechanical oscillations, which are of
great interest today. His fundamental contentions that
plants have a nervous system, that growth is pulsatile, that
plants are intelligent, capable of learning, remembering,
and responding to their environment in adaptive ways, are
now less outlandish than they seemed in the decades after
his death, when his work shifted to the outer limits of plant
physiology.
Acknowledgments – I would like to thank all the members of the Bose
Institute, in Kolkata and Darjeeling, for their hospitality, and for kindly
spending valuable time discussing the research of J.C. Bose with me.
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