FIGURE 3.

Analysis of total flash oxygen yield. A, histogram illustrating the total flash oxygen yield for wild type Arabidopsis and psbo1 mutant thylakoids under different ionic conditions. The CaCl₂ treatments also contained 50 μm ionomycin. The total oxygen yield is the sum of the oxygen yields observed on the first four saturating flashes. For the wild type, this value was 10.8 ± 2.6 V, and for psbo1, this was 5.3 ± 1.1 V under control ionic conditions (n = 4–13; error bars indicate ±1 S.E.). ^a,b, p < 0.05 using Student's t test (one-tailed). B, stability of the total flash oxygen yield during dark incubation at 24 °C under different ionic conditions. The time axis indicates the length of dark incubation. ▪, wild type decay curve under control ionic conditions; •, psbo1 control; ♦, psbo1 + 150 mm NaCl; ▴, psbo1 + 20 mm CaCl₂ + 50 μm ionomycin (n = 4–13, error bars ±1 S.E.). In some instances, the symbols are larger than the error bars. Treatment of wild type thylakoids with either 150 mm NaCl or 20 mm CaCl₂ had little effect on the stability of the total oxygen yield or other parameters examined in this study and are not shown.