Research reveals how plants perceive light

A study on the first published in "science" magazine - signal shows that the plant seems to be directly transported to the roots of the sun, to help them grow.

It is well known that light receptors in stems, leaves, and flowers regulate plant growth. Although the roots also possess these receptors, it is not yet clear how they perceive light in the dark depths of the soil.

Hyo-Jun and colleagues from the Seoul National University in South Korea, Lee, used a small flowering plant Arabidopsis thaliana as a model to study the phenomenon. They found that the stems of Arabidopsis, such as fiber optic cables, play a role in transmitting the light down to the root receptors known as phytochrome. This triggers the production of a protein called HY5 that promotes healthy growth of the roots.

The perception in the dark light. (image: Dr John Runions/Science Photo Library)

When these plants were transformed into phytochrome mutants, HY5 production began to decline. And when they have a HY5 mutation, the roots are stunted and the angle of extension is very strange.

To confirm that light is transmitted directly in the plant, rather than activating the signaling chemicals that travel through the roots, the researchers connect a light source to the stem of the plant by means of an optical fiber. The ground detector at the end of the root confirms that the light is transmitted directly.

What's more, they did not observe signs of a marked increase in root growth when they were treated with common plant signaling chemicals, such as sucrose, in the dark. This suggests that these chemicals do not drive growth.

The study also found that red light was the most efficient movement in plants. Lee said that the long wavelength of such light may be advantageous, because they can travel farther than the shorter blue and green wavelengths. At the same time, he says, most plants have phytochrome, which suggests that the direct transfer of light through the stem to the roots is a common mechanism used to optimize root growth.

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