Figure 2.

Absorption ESR spectra of the g ∼ 1.9 semiquinone-iron signal observed in PS II at 5 K (black trace) and 15 K (gray trace). Spectra scaled to account for Curie temperature dependence (i.e., 15 K spectrum × 3). The radical region around g = 2 (gray column) is dominated by light-induced radicals (D⁺) and has been omitted for clarity.