Micrographs of differential interference contrast (DIC) of H2O2 accumulation in wheat against Pst (race CYR 23) in DMSO-only and oryzalin treatments. (a) Mesophyll cells and guard cells showing DAB staining in control, 24 hai. (b) Positive DAB staining was detected mainly in guard cells treated with oryzalin, 24 hai. (c) Guard cells showing obvious and stronger reddish-brown H2O2 accumulation and mesophyll cells exhibiting the extension of plant cell wall apposition (CWA) in control, 48 hai. (d) Weaker DAB staining detected in guard cells treated with oryzalin, 48 hai. (e) Mesophyll cells and guard cell exhibit intensive H2O2 accumulation in control, 96 hai. (f) Mesophyll cells and guard cell showed slight H2O2 accumulation in oryzalin treatment at 96 hai. GT; germ tube; HMC; haustorial mother cell; SP; spore; and SV; substomatal vesicle. Scale bars = 25 μm.