Secrets of plant intelligence
We all know the plants do respond to stimuli as proved by the Eminent
Scientist, Prof. Acharya Jagadish Chandra Bose. Not only Prof. Bose proved this
phenomenon through various experiments, he further drew several similarities
between the life of plants with animals by using his invented plant growth
measuring instrument, the crescograph, and the resonant recorder.
However, do we know about the brain, senses, and thinking power of
plants or rather say plant intelligence? The matter is very intriguing and still
a point of research to Scientists. If you think a little about it, one plant called “touch-me-not” (Mimosa
Pudica) may easily come to your mind whose leaves fold when touched. One may
get more examples from either some plants whose flower petals open with the
sunrise and some insectivorous plants (e.g., Venus flytrap) that show quick
response in the presence of insects and catch them as prey. Surprisingly, if
the leaf-eating larvae of an insect come and start eating the leaves, then
immediately the larvae-resistant toxic chemicals begin to form in every cell of
the plant. Aren’t the fascinating examples of plant intelligence? Even more
bizarre, scientists have found, is that even if the plant is run in front of
the larvae by recording the sound of leaf food, the larvae-resistant toxic
chemicals soon begin to form in the plant! Scientists speculate that even
though the plant has no visual senses, it can sense external stimuli better. All
of these events are just witness to the response of plants to stimuli and
well-proven cases of plant intelligence.
If we look at the history of science, we can see that many years ago, in
the year 1880, legendary naturalist Charles Darwin gave an interesting idea by
observing the behavior of plants. He stated the very interesting fact that the
tip of the plant root which originates from the seed ‘radical’ can control the
movement and function of the plant. The plant root is a highly intelligent
organ that judges the quality of water and soil. In the soil, while absorbing
water and mineral salts, plant roots do outstanding jobs in controlling the
water balance, nutrition, growth, acid-base balance, and hormonal functions in
the plant body. This indicates plants’ actions are also guided by some
super-intelligent brain, much like the case of animals where the brain controls
and manages all the bodily functions. Such minute observations were recorded by
Darwin in his book “The Power of Movements in Plants” which many may not
be fully aware of people.
Subsequently, many scientists researched in this field of plant
intelligence and sensitivity towards stimuli and concluded that touch, sound,
melody, resonance, etc from the surrounding environment plays a significant
role in the same! However, the question arises that don't the plants need an
improved and active nervous system to respond to such direct and indirect
stimuli (viz. touch, sound, temperature)? And if so, where are the so-called
nerves and nervous systems located in the plants? A lot of research has so far
revealed many new facts and information.
Firstly, some special glutamate receptor proteins have been found in
plants, which act just as ‘neurotransmitters’ present in the animals.
Surprisingly, several plant proteins including, G-box protein, 14-3-3, has been
found to even stimulate the function of neurotransmitters in animals.
Furthermore, some special proteins have been discovered in both plants and
animals, which play crucial roles in nerve conduction.
With the discovery of the currently high magnification electron
microscope, scientists have further successfully observed not only the presence
of neurotransmitter-type proteins in the plant cell but also a full circular
sac-like ‘synapse’ structure present there. These synapses can transmit stimuli
from one plant cell to another in the vicinity. Besides, the phloem tissue
inside the plant's circulatory system also acts as the nervous-like system extends throughout the plant's body - delivering water and food to
specific places and at specific times according to the plant's needs.
Of note, the well-known plant hormone called ‘auxin’ is considered to be
a chemical of the ‘neurotransmitters' class according to scientists. Recently,
Dr. Frantisek Baluska (University of Bonn, Germany) tested and proved that the
auxin hormone in plants is transported through special sacs, in the same way,
that neurotransmitters work in animal cells. However, exactly how or in what
mechanism this phenomenon occurs in plants has not yet been fully discovered.
Many scientists also believe that the perception of plants is very
advanced. Evidence suggests that many microorganisms and fungi, like animals,
form friendly symbiotic relationships with plants, and that the plants can
'consider' which microorganisms or fungi will be useful for their own survival.
In hostile environments, a variety of characteristic adaptations of plants are
observed, which can only be found in organisms with advanced, sensitive nervous
systems.
One may also wonder about the time-maintenance by the plants, like the
time of the day a plant decides to bloom its flowers or start the process of
photosynthesis or time to form nectar with the arrival of pollinated animals!
In fact, with the understanding of the time of the day when it's really hot,
they can set up a special 'temperature protection system'. We know that in
animals there runs a special intrinsic rhythm of time, called a 'circadian
rhythm'. A clear pattern of ‘circadian rhythm’ can also be seen in plants and
scientists have revealed certain proteins regulating it specifically in plants.
Scientific studies have shown that plants have the ability to regulate the
circadian rhythm of each cell!
Conclusion
Scientist Claude Bernard (1813-1878) believed that as the environment
changes, so does the sensitivity of plants. He showed that by applying anesthesia
on plants, changes in germination, photosynthesis, movement, etc. of plants can
be seen, just like the animal body which becomes unresponsive following anesthesia.
Henceforth, every cell in a plant is just as sensitive as the nerve cells in an
animal. Yet many of the behaviors of plants, the techniques of their various
physiological work are mysterious but definitely give us strong hints of plant intelligence. Research is still going in this field so
that we get answers in the near future.
Dr. Juni Banerjee
Former Scientist and Asst. Professor (Amity University, Delhi, India),
Postdoctoral Research Fellow (University of Pennsylvania,
Philadelphia, USA).
Ph.D. Degree Holder (Jadavpur University, Kolkata, India)
References:
1. Tandon PN. Jagdish Chandra Bose & plant neurobiology. Indian J
Med Res. 2019
May;149(5):593-599.
2. Baluska F, Mancuso S, Volkmann D, Barlow PW. The 'root-brain'
hypothesis of
Charles and Francis Darwin: Revival after more than 125 years. Plant
Signal
Behav. 2009 Dec;4(12):1121-7.
3. Brenner ED, Stahlberg R, Mancuso S, Vivanco J, Baluska F, Van Volkenburgh
E.
Plant neurobiology: an integrated view of plant signaling. Trends Plant
Sci. 2006Aug;11(8):413-9.
4. Lam HM, Chiu J, Hsieh MH, Meisel L, Oliveira IC, Shin M, Coruzzi G.
Glutamate-receptor genes in plants. Nature. 1998 Nov 12;396(6707):125-6.
5. Baluska F, Samaj J, Menzel D. Polar transport of auxin:
carrier-mediated flux
across the plasma membrane or neurotransmitter-like secretion? Trends
Cell Biol. 2003 Jun;13(6):282-5.
6. Trewavas A. Green plants as intelligent organisms. Trends Plant Sci.
2005
Sep;10(9):413-9.
7. Robinson G., Hawes C, Hillmer
S, Jürgens G, Schwechheimer C, Stierhof YD, Viotti C,
Plant Physiol. 2018 Mar; 176(3): 1884–1888.
