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The study reveals the mechanism by which light sources are detected

The study reveals the mechanism by which light sources are detected

Plants can distinguish between the different amounts of light they receive and the way their cells react to it. So far, no clear explanation for this phenomenon has been found.
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Don't be fooled by appearances, The wonderful world of plants is much more than meets the eye. And when it comes to “vision”, although plants do not have eyes in the sense in which we know them, They have the ability to detect the source of light. But how do they do it?

This puzzle has been solved by researchers from University of Lausanne (UNIL) and Federal Polytechnic School of Lausanne (EPFL) in Switzerland. The study revealed that plants have Light-sensitive tissues in their stems that use optical properties to direct their growth.

The plant “sees” thanks to the air channels

Unlike other living organisms, plants do not have a vision system similar to eyes. However, it is amazing The ability to determine the origin of a light source is well known.

Detecting the source of light is especially important for plants, which use this information to determine the position of their organs as they grow, a phenomenon known as phototropism.

It turns out that Plants have something amazing in their stems called “air channels.”. These are the spaces between cells that facilitate not only the passage of air, but also… Limit the amount of light that passes through. They're like little light curtains inside the plants!

Magic in optics

The research used a common plant model in plant biology known as Arabidopsis thaliana plantspecifically a mutant version containing a The “surprisingly transparent” stem.“, said lead investigator A press release.

“We discovered that the natural milky appearance of the stems of young wild plants was actually due to the presence of air in the channels between cells located precisely in different tissues. In the mutant specimens, the air is replaced by a watery liquid, giving them a transparent appearance.”

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Christian Fankhauser, Director of the Center for Integrative Genomics at UNIL's Faculty of Biology and Medicine

These channels increase light dispersionEspecially in the hypocotyl – the part of the plant that grows from the seed – for seedlings. This has an impressive effect, Creating a light gradient is essential for an effective growth response – It's like an indoor light show on each plant!

Water and air in appropriate proportions

As shown in the study, light-sensitive tissue is used Optical properties of the air-water interface To generate a light gradient that is “visible” to the plant.

The index of refraction is a measurement that describes the degree to which light slows down as it passes through a material, compared to its speed in a vacuum.

“Air and water have very different refractive indices. This causes light to be scattered as it passes through the hypocotyl of a seedling. We have all observed this phenomenon when we admire a rainbow,” explained Martina LeGris, co-author of the study.

Arabidopsis thaliana plant
The study also allowed us to better understand the formation of channels between air-filled cells, which have numerous functions in plants, such as promoting gas exchange and allowing resistance to hypoxia (reduced oxygen supply) in the event of flooding.

Comparison between mutant and wild-type plants allowed the researchers to conclude that the internal composition of the tissue (water or air) is responsible for A mechanism that allows a plant to determine the direction of light.

Such studies provide new insight About how plant biology workspresents us with a botanical view of molecular mechanisms worthy of a green, bright round of applause.

News reference:
Fankhauser C, Legris M. The aerial channels generate a directional light signal to regulate the phototropism of the hypocotyl. Science (2023)