The focus is on the most widely studied wound response: the systemic synthesis in tomato of the defence proteins known as proteinase inhibitors (PIs). In wounded tomato seedlings, the severity of the wound is a major determinant of the type of wound signalling. Minor wounds produce outcomes that are consistent with the transport in the phloem of a chemical elicitor of PI synthesis. Severe wounds produce outcomes that are consistent with the distribution of elicitors of PI synthesis and of electrical activity by hydraulic dispersal in the xylem. The main electrical events associated with severe wounds are action-potential-like depolarisations in the sieve-tube-element/companion cell complexes; these events are considered in relation to the use of the terms action potential and variation potential.
Rhodes, J. D., Thain, J. F., & Wildon, D. C. (2006). Signals and signalling pathways in plant wound responses. In Communication in Plants: Neuronal Aspects of Plant Life (pp. 391–401). Springer-Verlag Berlin Heidelberg. https://doi.org/10.1007/978-3-540-28516-8_26