Figure 3.

Characterization of Photosynthetic Electron Flow in Wild-Type and koLhcb4 Plants.

(A) Dependence of the LEF rate on light intensity in wild-type (WT) and koLhcb4 leaves. LEF rate is calculated as ϕ_PSIIPSII·PAR·A_leaf·fraction_PSII (see Methods for details).

(B) Photosynthetic oxygen evolution in saturating CO₂. Rate of oxygen evolution was measured on whole leaves during illumination with various levels of actinic red light.

(C) Amplitude of qL measured at different light intensities on wild-type and koLhcb4 leaves. qL reflects the redox state of the primary electron acceptor Q_A, thus, the fraction of open PSII centers.

(D) and (E) Measurement of state I–state II transition in the wild type (D) and koLhcb4 (E). Upon 1-h dark adaptation, plants were illuminated with blue light (40 μmol photons m⁻² s⁻¹, wavelength <500 nm) for 15 min to reach state II. A far-red light source was then superimposed on the blue light to induce a transition to state I. Values of F_m, F_m′, and F_m′′ were determined using light saturation pulses (4500 μmol photons m⁻² s⁻¹, 0.6 s). a.u., arbitrary units.

(F) and (G) Dependence of the P700 oxidation ratio (ΔA/ΔA_max) on light intensity. ΔA/ΔA_max was measured on wild-type and koLhcb4 leaves at varying actinic intensities, exciting either PSII + PSI (λ = 630 nm; [F]) or PSI only (λ = 730 nm; [G]).