dimanche 8 avril 2018

127- The spirit of plants -11- 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.

 The sensitive keeps in memory the stresses that it underwent during forty days. (Littlemisspurps / Flickr)

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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