Figure 7.

Fluorescence Analysis of Nigericin-Sensitive and Nigericin-Resistant NPQ Components in Wild-Type and npq1 Genotypes of Arabidopsis.

(A) Wild-type and npq1 leaves were either left in the dark or illuminated (1200 μE m⁻² s⁻¹) for 15 min at room temperature to induce NPQ and zeaxanthin accumulation (in the wild type). Leaves were then rapidly infiltrated with either 5 mM Hepes, pH 7.0, or 50 μM nigericin to abolish ΔpH. F_m level was measured using a video imaging fluorescence system as described in Methods. The time required for infiltration and measurement was ∼1 min. a.u., arbitrary units.

(B) Chlorophyll fluorescence intensity determinations in Arabidopsis wild-type leaves for F_m and F_m′. After each light window, the F_m′ value was measured on leaves rapidly infiltrated with 50 μM nigericin.

(C) Comparison of nigericin-resistant NPQ component in wild-type and lhcb5 leaves, measured as in Figure 7B. Data sets with a significance level of P < 0.05 according to Student's t test are marked with an asterisk.