Measurement of Electropotential Waves in Intact Phloem Sieve Elements Using Microelectrodes

Electropotential waves (EPW) are involved in plant responses to both abiotic and biotic stresses. Three different types of EPWs have been identified: action potential, variation potential, and system potential, all of which have been indicated to participate in phloem-based communication between plant organs. In this chapter we describe in detail how to measure EPWs in plants, including how to access the phloem, and how to insert microelectrodes. Such experiments can be used, for example, to study the local and systemic signaling in response to diverse stimuli like microbial threat or herbivore attack.