Plants don't have eyes, yet they detect the source of light. A joint study led by Prof Christian Fankhauser at UNIL and EPFL researchers found that plants use their light-sensitive tissue to create a light gradient, pinpointing the light's direction. Published in Science, this discovery unravels how plants manage phototropism, helping them optimize sunlight absorption for photosynthesis.

The study stemmed from a transparent-stemmed mutant of Arabidopsis thaliana, indicating altered light response. Investigating this, UNIL and EPFL researchers noticed air-filled channels in normal stems, contributing to their milky appearance. However, mutant stems replaced air with a liquid, altering their transparency.

These air-filled channels serve a vital purpose: they enable the plant to establish a light gradient, indicating the light source. The differing optical properties of air and water inside the tissue scatter light, a phenomenon akin to seeing a rainbow. This phenomenon aids plants in arranging their organs, like leaves, for optimal light capture, essential for photosynthesis.

Additionally, this study shed light on the functions of air-filled channels beyond light gradients. These channels support gas exchange and aid in surviving oxygen depletion during flooding. Understanding their development remains a significant scientific puzzle, but this research offers valuable genetic insights into their formation and maintenance.

This breakthrough provides profound insights into how plants sense light's direction and organ positioning for efficient photosynthesis.