How plants determine where light comes from

Wild-type ( left ) and mutant ( right ) Arabidopsis thaliana seedlings with light from the right. The mutant does not react to the light source. Martina Legris © CIG-UNIL - With no visual organs, how can a plant know where light is coming from? In an original study combining biological and engineering expertise, the team led by Prof. Christian Fankhauser at the University of Lausanne, in collaboration with colleagues at EPFL, has deciphered a novel mechanism using the interface between air and water to generate a gradient of light "visible" to the plant. These results have been published in the journal "Science". The majority of living organisms (micro-organisms, plants and animals) have the ability to determine the origin of a light source, even in the absence of a vision organ comparable to the eye. This information is invaluable for orienting oneself or positioning oneself optimally in the environment. This is particularly important for plants, which use the direction of light to optimize the position of their organs, a phenomenon known as phototropism.