Table I.
Comparison of basic characteristics of APs, VPs, and SPs
| Characteristic | APs | VPs | SPs |
|---|---|---|---|
| Induction | Voltage threshold | Rapid turgor increase | Plasma membrane depolarization |
| Propagation | Self-propagating | Non-self-propagating | Self-propagating |
| Rate | 20–400 cm min−1 | 10 s to several minutes | 5–10 cm min−1 |
| Mechanism | Activation of ion channels (Ca2+, Cl−, K+) | Inactivation of the H+ pump | Activation of the H+ pump |
| Ion movements and ΔV | Ca2+ triggers Cl− efflux and ΔV | Causalities unclear | Ion movements follow voltage |
| Direction | Depolarization | Depolarization | Hyperpolarization |
| Duration of initial voltage change | <20 s | 10 s to several minutes | 8–12 min |
| Signal | All or none | Graded signals of variable size | Signals depend on stimulus |