Figure 4.

Effect of external [Ca²⁺] on cytosolic free [Ca²⁺] (pCa_C) and membrane potential (Em) of alfalfa root hairs before and after the addition of 0.1 μm NodRm-IV(C16:2,S). Shown is the Nod factor response in the presence of high extracellular [Ca²⁺] (a) and in the presence of low extracellular [Ca²⁺] (b). “Ca²⁺-free” refers to the addition of a solution with no extra Ca²⁺ added (i.e. 1–2 μm free Ca²⁺, as measured with a Ca²⁺-selective microelectrode within the root hair space). pCa 7.44 refers to a solution with 0.01 mm free EGTA. The initial transients on the Ca²⁺ traces arise from the different response times of the two electrodes. Kinetics are representative examples of four recordings each carried out under equivalent conditions.