THE SPIRIT
OF PLANTS - ELECTRIC ACTIVITY
This
article, published in March 2016 in the Swiss periodical Le Temps, is
self-sufficient, so I will refrain from commenting.
"Are
plants animals like any other?
Memory,
pain, vision, smell ... Botanists discover in plants always more capacities
that were thought proper to the animal world. The debates are passionate.
Far from the clichés on the green
and passive plant, plant biology has been observing for fifteen years
surprising faculties that were thought to be reserved for the animal world.
Plants have multiple sensory abilities that allow them to communicate with each
other and with insects, to adapt to crisis situations, to memorize, and to the
great surprise of researchers, their biochemical activities are linked to
mysterious electrical activities.
At the department of molecular
biology of plants, at the University of Lausanne, the team led by Edward Farmer
works on one of the latest discoveries that amazes the world of research: the
electrical activity of plants.
The thale cress is a frequent model
in plant biology. (Carl Davies, CSIRO)
When they are injured for example,
they emit electrical signals that pass from one point to another. "We
wondered if these electrical signals generated when we hurt the plant can
trigger biochemical defense mechanisms," said Edward Farmer. Because the
defense proteins are not only produced in the attacked parts, but also in the
healthy parts.
Is there a plant neurobiology?
Using the model of thale cress
(Arabidopsis thaliana), the team was able to identify the genes that trigger
the electrical signal and confirm the link with the activation of defense
proteins away from the injury. The results published in 2013 in Nature
identified three GLR (Glutamate Receptor-Like) genes, similar to those of
animals, involved in this electrophysiological process. "What is
surprising is that these genes are very similar to the genes in the fast
synapses of the human brain, whereas a plant has no neurons. It's very
intriguing and challenging, "Professor Farmer enthuses.
Any biological cell has an electrochemical
membrane potential that acts as a small polarized cell, but electrical
transmission from one plant cell to another over a long distance remains an
enigma. With an average of 8 to 10 cm per minute - "a bit of the speed of
a caterpillar walking on a leaf" - the electrical signal has a
heterogeneous speed and "this in-between is a real headache for
research" he adds.
"Plants
also have processes of information, memory, decisions, problem solving."
The many and confusing similarities
between the electrical activity of plants and the nervous system of animals
still give rise to debates, sometimes heated, in the community of biologists.
Long before the work of Edward Farmer, Stefano Mancuso of the University of
Florence and Frantisek Baluska of the University of Bonn emphasized in their
work the importance of the "synaptic" activity of plants. So much so
that in 2005, Mancuso for the first time used the term "neurobiology"
plant by founding with Baluska the International Laboratory of Plant
Neurobiology.
Like many colleagues, Farmer
refutes this name because the plant has no neuron and it is not scientific
according to him to make such comparisons.
Diffuse
brain
On the other hand Baluska
emphasizes that "what is important is that most molecules responsible for
communication and neuronal activities in the human brain are also present in
plants with very similar functions. The process is very close and in a way
implies that plants also have processes of information, memory, decisions,
problem solving ". How to explain this mechanism when the plant does not
have a brain?
"Plants are able to produce
and emit electrical signals on every cell in their body. From this point of
view there is a kind of diffuse brain, whereas in animals everything is
concentrated in a single organ ", adds Mancuso.
Director of research at the
National Institute of Agronomic Research (INRA) in France, Bruno Moulia puts
that into perspective, because "the trap with plants is that they realize
many functions - such as vascular movement, muscle - with the same tissues. The
issue of plants synaptic activity is troubling but we can’t yet decide. "
Seismograph
trees
In Japan, researchers have long
observed that trees have an abnormal electrical activity that occurs 3 to 4
days before an earthquake and intensifies with the approach of D-Day. But the
mechanism does not yet allow to locate the epicenter and the magnitude of an
earthquake.
"The
memory or learning of plants is not comparable to ours."
Thanks to more than 700 sensory
sensors listed in the vegetable world, plants constantly analyze their
environment to measure temperature, humidity, light, etc. They have no eyes and
yet they see, they have no nose and yet they smell, they have no ears and yet
they react to sound waves ...
Many studies have also shown that
following a stress (climate, torsion, etc.) plants are able to remember and
adapt to their environment. This memory varies from a few days to forty days
for the sensitive (Mimosa pudica) for example, which according to the Mancuso
team also shows learning abilities.
The memory
of plants
In Bruno Moulia's laboratory in
Clermont-Ferrand, it has been shown that the plant is even capable of doing
certain "calculations". However, Francis Hallé, a French botanist,
warns that this is not a "memory or learning comparable to ours". A
plant that you rarely water, for example, will be used to living in drought,
and it remembers. On the other hand, if you water it a lot, the day you don't water
it, it dies. Because the plant also depends on what happened to it in earlier
times."
This memory is generally activated
with the expression of a previously inactive gene. "Genes can be
chemically modified by environmental factors, such as stress, and these epigenetic
modifications can in some cases be passed on to the next generation. This
genome sensitivity is surprising and we are just beginning to explore the scope
of epigenetic control of plant development”, says Lincoln Taiz, professor
emeritus at the University of California.
If humans have nearly 25,000 genes,
plants often have many more, such as rice that has more than 40,000. While the
animal has the opportunity to move, the plant has finally found its answers in
richness and genetic variability. "A guarantee of longevity," assures
Francis Hallé for whom the most important remains undoubtedly yet to discover."
To
learn more about plants' abilities to "perform mathematical
calculations" http://culturagriculture.blogspot.com.es/2015/11/58-spirit-of-plants-3-mathematics.html
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