Figure 3.

Effective Quantum Yield of PSII, Oxygen Evolution, and Multielement Chromatogram of the Wild Type, pam71-1, pam71-2, and pam71-1_{Pro35S:PAM71-GFP}.

(A) Chlorophyll a fluorescence induction curves were recorded in the range 0 to 856 µmol photons m⁻² s⁻¹ for the wild type (left panel) and pam71-1 (middle panel) and plotted as values from eight individual plants (±sd) (right panel) displayed as light response curve of the effective quantum yield of PSII Φ_II [(F_M′ − F_t)/F_M′]. Saturating pulses (SP) were applied as indicated. The plants were dark-adapted for 30 min prior to measurement. Φ_II was recorded following illumination for 30 s at the appropriate PAR. F_M′ and F_t are indicated for the wild type at 37 µmol photons m⁻² s⁻¹ (left panel).

(B) Oxygen evolution (nmol O₂ mL⁻¹) of the wild type (left panel) and pam71-1 (middle panel) was measured over the indicated time in isolated thylakoids adjusted to 30 µg chlorophyll mL⁻¹ and using DCBQ as an external electron acceptor. Reactions were started with the application of actinic light (AL) at 500 µmol photons m⁻² s⁻¹. Oxygen evolution rate (µmol O₂ mg chlorophyll⁻¹ h⁻¹) was calculated from two independent thylakoid preparations including three replicates (right panel). The data are means ± sd (n = 6).

(C) Size exclusion profiles were recorded for the nonoxide ion ⁵⁵Mn⁺ and the oxide ion ⁴⁸SO⁺ in the wild type (left panel) and pam71-1 (middle panel) and given as ion intensities (counts 10⁵ s⁻¹). Individual ⁵⁵Mn⁺ fractions were assigned to PSII dimers/monomers = PSII_di/mono and PSII supercomplexes = PSII_super according to Schmidt et al. (2015). Quantification of the Mn:S stoichiometric ratio (as described in Methods) is shown for a representative sample (right panel) out of five samples derived from independent thylakoid preparations.

(D) to (F) Analysis of pam71-2 and pam71-1_{Pro35S:PAM71-GFP} was performed as in (A) to (C), respectively.