Figure 2.

The Action Potential in Chara Elicits a [Ca²⁺]_i Increase.

A Chara internode cell, which had been injected with aequorin, is stimulated electrically to induce an action potential (top trace). Following closely is a sharp increase in the photomultiplier current indicating Ca²⁺-dependent light emission from aequorin (bottom trace). Bar = 2 s. (Figure courtesy of Williamson and Ashley, 1982, Figure 2a, with permission of Nature Publishing Group http://www.nature.com/).