dimanche 30 juillet 2017

110- The spirit of plants -9- Balance


I found the following article on a very interesting French blog, which I will have occasion to quote other times, "Graines de Mane" (Seeds of Mane), devoted, as its subtitle says, to popularization and debate about agriculture (https://www.grainesdemane.fr/2017/02/08/plantes-nont-tete-tourne/).

In this case, it's a curious subject, insofar as this question is not usually asked.
Yet, as you will be able to verify, this is an important question, and the similarities with animal world are surprising.

"Plants don't feel dizzy

Often agitated by the wind, plants remain standing. How do they do it? Researchers at INRA [French National Institute for Agronomic Research] have identified mechanisms that allow plants to maintain the balance.

The wind is one of the (many) natural enemies of the farmer. In the event of too strong storms, plants can overturn, that's to say lie down, to become non-harvestable in the end. Global cereal yield losses are estimated at 10% due to storms. Despite this, plants have a remarkable ability to stand, much more than us!

Shaked by the wind, the reed bends but does not break. Charles and Francis Darwin had already highlighted in their time the ability of plants to grow in a given direction. Thus, a plant always grows towards light (phototropism) or gravity (gravitropism), causing its roots to grow downwards and germinate upwards. Forcing a plant to grow horizontally and it will always end going upward.

Plants also have an inner ear
To understand the functioning of the mechanisms of plants balance, let's stop for a moment on ours, governed by the inner ear. In this, our balance is made by a so-called otolitic system, which is a set of small pebbles caught in a sensitive gel. The deformation of the eyelashes, due to the action of gravity on the pebbles, allows our inner ear to locate the vertical. However, when we are in a merry-go-round, for example, we lose the sense of gravity. Our inner ear is then incapable of distinguishing the acceleration due to gravity, of other forces, such as centrifugal force, for example.
Plants also have an equivalent of the inner ear: the statocytes. The statocytes are cells arranged throughout the stem of the plant, which contain small grains of starch called statoliths. Until now, research has demonstrated a similar function of the statocytes to that of the inner ear: the sedimentation of statoliths exerts pressure on the statocyte wall and allows the plant to detect gravity. This idea suggests that plants have a sense of balance comparable to that of humans and therefore they are not able to distinguish the gravity of another force, the wind for example. The pressure exerted on the statoliths would be the result of all the forces in an undifferentiated way.

A more acute sense of balance than humans?
Another hypothesis suggests that it's not the pressure exerted by statoliths that allows plants to "feel" gravity, but a sensor systems that detect the position of small starch grains. This idea stems from recent research carried out jointly by INRA, CNRS [French National Center for Scientific Research] and Blaise Pascal University. The researchers formed a carousel for plants, consisting of centrifuges with two axes of rotation, as they exist for astronauts training. They then subjected to centrifugal forces hundreds of plants, many of them cultivated like wheat, lentil or sunflower. They studied, for long periods, the growth of plants under these conditions, with a different angle compared to the actual gravity.
The story does not say whether the plants had fun in the carousel, but it shows on the other hand that they have managed to grow by straightening independently to the intensity of the centrifugal force they suffered. Plants thus can feel the verticality independently of the other forces to which they are subjected, and this permanently. The positioning of the statoliths, and not just the pressure they exert, would allow the plants to detect their verticality. Even shaken by the wind, plants would be able to keep their verticality.
Unlike us, they would not feel dizzy.

These recent discoveries of balance of plants mechanisms, can have very important applications in the decades to come, especially in varietal improvement, to conceive crops less sensitive to overturning. If this track should not make us forget that the overturning of plants can also be due to other agricultural factors (too much nitrogen for example), this is perhaps one of the many ways forward for securing yields against the vagaries of the climate.

If you want to learn more :

Here is another surprising characteristic which shows that the more one studies the plants, the less one finds a profound difference between the vegetable and the animal world.

A sign to call the vegans to more reason?
In the end, science shows us that most animal characteristics are also present in plants, although in a different way, since adapted to their particular condition.

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