Figure 6.
Measurement of Trans-Thylakoid ΔpH.
(A) The light-dependent quenching of 9-AA fluorescence in intact chloroplasts was quantified as a measure for trans-thylakoid ΔpH.
(B) Time course of violaxanthin deepoxidation in wild-type and mutant plants. Leaf discs from dark-adapted leaves were illuminated at 450 μmol m−2 s−1 (white actinic light). At different times, discs were frozen in liquid nitrogen and total pigment extracted.
(C) Amplitude of light-dependent quenching of 9-AA fluorescence measured at different light intensities on wild-type and koCP24 intact chloroplast. Inset: traces of 9-AA fluorescence emission (430 nm) during ΔpH buildup (induced by red actinic light, 450 μmol m−2 s−1) shows a slower lumen acidification in mutant chloroplasts. AL, red actinic light turned on.
(D) Amplitude of violaxanthin deepoxidation was measured on leaf discs from the wild type and koCP24 after illumination (10 min) at different light intensities. All data are expressed as mean ± sd (n = 4). Significantly different values according to Student's t test (P < 0.05) are marked with an asterisk.