Plants encode the spatial distribution of light based on a vectorial representation

In order to survive in harsh and changing environments, plants shape their morphology to maximize light incidence and minimize mechanical load, building on tropisms - the redirection of growth in the direction of stimuli such as light and gravity. The remarkable ability of plants to identify optimal directions of growth in complex environments, suggests underpinning computational abilities, such as the integration of sensory information over space and time. Here we focus on the spatial integration of light signals, following the phototropic response of sunflower seedlings exposed to two opposing light stimuli of different intensities. We develop a vectorial model to account for spatial integration of multiple light stimuli, informed by experiments, and simulations recover the main experimental features. Combining theory with experiments we find that the seedlings respond to the vectorial sum of transduced light signals, and further corroborate our model by introducing a third light source.