Fig. 6. Stimulation of luminescence by increasing [K⁺]. (A) Sample records of luminescence stimulated by addition of solutions containing high (31 mmol l^-1) or low (6 mmol l^-1) [K⁺]. The box beneath the x-axis marks the time of injection (controlled by a syringe pump). (B) Dose-dependence of stimulation by K⁺. Integrated luminescence (over 200 s total) stimulated by addition of [K⁺] solutions normalized to total luminescent capacity (K⁺-SL/TLC) for each sample tested (N=4-7). Data are expressed as means ± S.D. and are a function of [K⁺] in the test solution added rather than the final [K⁺], because much of the stimulation occurs before mixing of solution can be completed, especially at high [K⁺] (N=4-7 for each stimulus tested).