PC+ = f(P700+) during far-red illumination. Curve 1, □, computed from Fig. 2 B and C, curves 3; ▪, computed from Fig. 4B, curve 2. Curve 2, computed from Fig. 4B, curve 1. Curve 3, computed from Fig. 2 B and C, curves 1. Curve 4, theoretical function assuming a midpoint redox potential of 465 and 330 mV for P700 and PC, respectively.