Figure 2.

Typical systemic apoplastic voltage signals (AP and SP) measured successively on one leaf. A, Following a cut injury, 10 mm Glu was applied to one leaf of H. vulgare and an AP was measured on a distant leaf (distance in this recording of 33 cm) with a blunt microelectrode positioned in the substomatal cavity of an open stoma. B, After the stimulus site was rinsed with AAF, a second Glu application was made that did not trigger an AP but a hyperpolarization, an SP. Representative examples of five equivalent measurements each are shown. E(apo), Apoplastic voltage.