Figure 1.Induction of ROS production in Arabidopsis guard cells’ chloroplasts by ABA and MJ. (A) Leaf disks were prepared from wild-type plants and treated with ABA and MJ. After incubation of leaf discs in solution with the phytohormones, cells were loaded with H₂DCFDA as described in methods. Shown are representative images of single section confocal microscopy (1 μm thick) of guard cells from the different treatments. Scale bar = 10 µm. (B) Quantification of the H₂DCFDA-dependent fluorescence of individual chloroplasts shown in (A). Quantification was done using ImagePRO-Plus program from projected images of 2–3 confocal Z stack sections of individual chloroplasts, as described in methods. Shown is a representative one of three replicate experiments. n = 30 chloroplasts from 10 guard cells sampled from three different young rosette leaves (± SE). R.U. relative unites.