Spatio-temporal dynamics of the electrical network activity in the root apex. A multi-electrode array (MEA) study

Root cells have been a popular research tool for decades because they allow easy access to individual cells for electrophysiological recording and stimulation, pharmacologic manipulations and high resolution microscopic analysis. However, it is technically difficult to record from and stimulate more than three cells using standard intracellular microelectrodes, and those cells usually die within minutes or, barely, hours. Thus any distributed/synchronized electrical activity is missed without a multi-unit approach. Multi-electrode arrays (MEAs) provide a tool to record from and stimulate many cells (up to hundreds) of the same root apex, concurrently and non-invasively. Since the array substrate is made of transparent glass, cell morphology can be easily monitored by the use of an inverted microscope or using fluorescent labels and a confocal. Here, for the first time in plant science, we use a 60-channels MEA to study in thick root apex slices the spatio-temporal characteristics of the electrical network activity. We observed an intense spontaneous electrical activity as well as stimulation-elicited bursts of spikes locally propagating. Our data indicate that synchronous activity of the cells emerges spontaneously throughout the time evolution. The strict similarity of the electrical behaviour recorded with the behaviour showed by neural cell culture may reflect an intrinsic capacity of the root apex to generate functional networks.