Introduction
It is known that plants react to many stimuli that are present in the growing environment, such as physical (i.e. light, temperature, humidity), chemical (i.e. nutrient concentration, volatile compound, chemical signal in the ground, ...) or biological (i.e. pathogens, symbiont).
How plant can interact with those stimuli ? Via allelopathy, it is accepted that they are able to communicate between them. But, what are the vector of this communication? the soil, the air, the water or some living organisms. In this study case, we tried to explore this question following two steps :
The first one is based on an in-vitro experimentation developed by a group of American students. Their purpose was to identify four components responsible of the communication between plant: there must be clear motivation or reason for the communication, the presence of a signal and/or channel, a receiver, and a clear response. To identify a communication between plants, they build an in-vitro system physically separated in three sections, each of them had a different nutrition condition. They hypothesized that this discrimination in term of nutritive context would be the motivation or the reason to induce communication, so three plants were placed into each compartment. They hypothesized that the signal would be transmitted by chemical molecules excreted by the roots, called exudate, and that the channel will be passive, through the medium or active via the mycorrhizae, that is the reason why they used pre-mycorrhized plants. To allow the perception of the signal by a receiver, roots of each plant were placed in a shared compartment without any physical contact in the middle of the systems (Picture 1) . Finally, they wanted to observe a clear response, such as a root direction growth that would indicate the perception of a more favorable nutritive context.