Light is not only a source of energy for plants but also an important signal which regulates many light-dependent growth processes allowing it to effectively adapt to its environment.

Light is first detected by photoreceptors in the shoot of a plant. For more than three decades, scientists have been speculating whether roots are also able to perceive light. A new study appears to confirm that is the case.

Previous studies had shown that a special photoreceptor in plants which detects light of the wavelength red/far-red is surprisingly also expressed in the roots. However, it remained unclear how this root photoreceptor was activated. In an interdisciplinary effort, molecular biologists and optical physicists developed a highly sensitive optical detector along with the idea to compare plants with “blind” and “sighted” roots.

They used plants of the thale cress Arabidopsis thaliana, a model organism in plant research, which were genetically modified in a way that the photoreceptor was only silenced in their roots, but not in their shoots. Hence, these plants had “blind” roots. The scientists grew these modified plants along with control plants; their roots were in the dark soil and their shoots exposed to light, just like in nature. The optical detector system was used to measure light which was transmitted in the stem down to the roots.

The results showed that roots do indeed perceive light even though they are typically below the ground.

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Craig DiLouie

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