“It is a painting whose appearance changes a little, it becomes richer the more you look at it. Gauguin likes them very much. He told me about them, among other things: “This, this is the flower”. You know, Janine has the peony, Quest has the althaea, but I have him sunflower in a way”, he had written in a letter Vincent Van Gogh to his brother Theo.
The great Dutch painter began to paint the famous sunflowers in the summer of 1888, which were particularly loved by his French colleague Paul Gauguin. Van Gogh’s paintings depict sunflowers in different stages of life, from full bloom to death, and were considered groundbreaking for the yellow hues in their open petals.
But how do the sunflowers or sunflowers understand where the sun to turn to its beneficial rays?
A new study overturns what scientists believed until now. THE research published in the scientific journal PLOS Biology actually reveals that their mechanism of action, responsible for heliotropism, still remains… mystery.
Until recently, experts attributed the behavior to plant phototropism, i.e. the movement in the direction of the light stimulus that favors their growth. They had assumed, therefore, that sunflowers had the same ability based on the same molecular mechanism, the phototropin which reacts to light in the blue part of the optical spectrum.
Sunflowers turn to the sun and push their “head” west during the day to develop their left side, while they turn east to develop their right side.
Phototropin, therefore, seemed to be the key player in this case as well in helping the plant recognize which side to grow more, but the report by plant biologists at the University of California, Davis, changed the facts.
Stacey Harmer’s team analyzed the gene expression of sunflowers in two different conditions: At interior workshop spaceunder constant lighting conditions, and at nature. By checking which genes are activated throughout the day, it is possible to identify the molecular mechanisms that favor plant growth. Plants grown in the lab, with a constant light source, grew directly toward the light, activating phototropin-related genes. In outdoor plants, however, there was no apparent difference in phototropin between one side of the stem and the other throughout the day.
“The results seem to they exclude the “jamming” of the molecular path associated with phototropin, but we didn’t find any more precise evidence,” Harmer said, adding that this was surprising.
In short, the operation of the sunflower is shrouded in mystery. Blocking blue, ultraviolet, red light with shade boxes had no effect on the plant’s ability to recognize the direction of the sun. And this, according to the experts, means that the heliotropism it follows a series of different molecular paths, responding to different wavelengths according to its needs.
To discover, however, which molecule is responsible, we will have to wait for the results of further investigations, which are currently underway.
What impresses the experts is that the sunflowers that were moved from the laboratory to the outdoors, immediately began to “follow” the sun. Strong gene expression was then observed on the side of the stem that did not “see” the light, which however was not detected the next day. This leads scientists to estimate that the sunflower made a… restart in an attempt to better adapt to the new light source.
What Harmer emphasized is that “what is observed in a controlled environment such as a growth chamber may not have the same behavior in the real world.”
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