Visualization of H₂O₂ by CeCl₃ staining.

<p>No staining was observed in cells of mock-inoculated controls (A: 96 hpi). At the AIS H₂O₂ accumulation (arrows) was detected within cell walls 48 hpi (B) and inside mitochondria (M) and plastids (P) 96 hpi (inset in C). Note that plastoglobuli (white asterisks) within chloroplasts (C) and plastids (P) increased in size with advancing infection (best seen in B and E when compared to A). At the IS small dark precipitates of H₂O₂ staining (arrows) were observed 24 hpi (D) in cell walls (arrows) but not in the other cell compartments and 48 hpi (E) in cell walls, in the matrix of mitochondria (M, inset upper right corner) and stroma of chloroplasts (inset lower right corner). Dark precipitates (arrows) were observed at the IS throughout the cytoplasm of leaf cells 96 hpi (F). At the IS 96 hpi only remnants of organelles such as plastids (P) and nucleus (N) could be found in the condensed cytoplasm. H = hyphae, ICS = intercellular spaces, Px = peroxisomes, St = starch, V = vacuoles. Bars in inset of A, C, and E = 0.25 µm, D = 0.5 µm. Bars in all other images 1 µm.