Compartment specific glutathione labeling density after long term light stress. Graphs show the amounts of gold particles bound to glutathione per μm2 in mesophyll cells of Arabidopsis thaliana Col-0 plants (black squares) and the Arabidopsis mutants pad2-1 (black circles) and vtc2-1 (black triangles) after the exposure to different light intensities for 14 d. n > 20 for peroxisomes and n > 60 for other cell structures. No or only very few gold particles bound to glutathione were detected in vacuoles and gold particle density could therefore not be evaluated for this cell compartment. Data are means with standard errors. Significant differences were calculated within one line of plants between control conditions (exposure to 150 μmol m-2 s-1) and the same line exposed to the other light intensities by using the Mann Whitney U-test; *, ** and ***, respectively, indicate significance at the 0.05, 0.01 and 0.001 levels of confidence.