Measuring surface potential changes on leaves.

We provide here a detailed protocol for studying the changes in electrical surface potential of leaves. This method has been developed over the years by plant physiologists and is currently used in different variants in many laboratories. The protocol records surface potential changes to measure long-distance electrical signals induced by diverse stimuli such as leaf wounding or current injection. This technique can be used to determine signaling speeds, to measure the connectivity between different plant organs and-by exploiting mutant plants-to identify transporters and ion channels involved in electrical signaling. The approach can be combined with the analysis of mRNA expression and of metabolite concentrations to correlate electrical signaling to specific physiological events. We describe how to use this protocol on Arabidopsis, looking at the effects of leaf wounding; however, it is broadly applicable to other plants and can be used to study other aspects of plant physiology. After wound infliction, surface potential recording takes ∼20 min per plant.