Learning to grasp in pea plants

Although plants are sessile by nature, they are very attuned to their environment and are capable of a variety of movements. For example, climbers such as pea plants (Pisum sativum L.) need to find a potential support in order to grow vertically and gain greater exposure to light. Evidence has been demonstrated that pea plants can sense the presence of potential supports in the environment and flexibly adapt their movement to clasp it. How pea plants control and perfect this behavior during growth remains unexplored. Here, we attempt to shed light on this matter by characterizing the behavior of the apex and the tendrils (i.e., modified leaves that are capable of coiling around a potential support) at each leaf. Three-dimensional (3D) kinematic analysis was used to characterize the movements of pea plants from the seed’s germination until the support coiling. A control condition in which plants grew in an environment lacking potential support was also considered. We hypothesized that plants accumulate information and resources through the circumnutation movements (i.e., the oscillatory movements around the central axis of the plant during their growth) of each leaf. And, they then use this information to generate the kinematic coordinates for the final launch towards the potential support. Results suggest that the development of a functional approach to grasping movement may involve an interactive trial-and-error process based on continuous cross-talk between leaves. Thus, the implementation of an appropriate attachment plan in pea plants involves some form of adaptation driven by an iterative algorithm.