Effect of H2S donor NaHS on cell viability in barley aleurone layers. ((a), (b)) Aleurone layers are incubated in different concentrations of NaHS (0, 0.005, 0.025, 0.05, 0.25, and 0.5 mM) for 5 d at 25°C. After staining with trypan blue, the images are obtained by light microscopy with blue or purple indicating dead cells. ((c), (d)) Time course of PCD in barley aleurone layers treated with NaHS (H2S) or water (Control). Aleurone layers are incubated in 0.25 mM NaHS or water for 0, 1, 3, 5, and 7 d at 25°C and are stained with trypan blue. Digital images of barley aleurone layers ((a), (c)) and percentages of dead cells ((b), (d)) are shown. Bar, 50 μm. Data are means ± SD of three different aleurone layers per treatment.