Figure 2.

Effects of addition of MV, light irradiation intensity, and subjective time on intracellular ROS levels. (A) Wild type cells were incubated without MV (w/o MV) or with 50 µM MV (w/MV) under three levels of light intensity (0, 10, and 100 µmol m⁻² s⁻¹) for 30 min. Fluorescence intensity of control samples (w/o H₂DCFDA) was subtracted from the fluorescence intensity of samples with H₂DCFDA, and the differences in fluorescence between with and without MV at each light intensity level are presented. Fluorescence intensity was measured from three biological replicates in each experiment. Values are means ± SD (bars) results from three independent experiments (therefore, each bar is the average of n = 9). Student’s t tests were significant (*P < 0.05). (B) Dependency of ROS levels in wild type cells on circadian time. Wild type cells sampled at various subjective times were treated with 10 µmol m⁻² s⁻¹ light irradiation for 30 min, with or without 50 µM MV. Generated hydroxyl radicals were determined by spin trapping EPR spectroscopy with 4-POBN. Values are means ± SD (bars) of three biological replicates. Significant differences from samples without MV were evaluated by student’s t tests (*P < 0.05, **P < 0.001).