Figure 11.

Possible paths for O₃-dependent generation of ROS leading to cell death in tobacco cells. There are two likely paths starting from O₃. One pathway is a pH-dependent and purely consisting of radical reactions. This pathway is dominant in alkaline conditions since O₃ can readily react with bulky OH^- to yield HO^. and O₃^-. The other likely path starting from O₃ proceeds at physiological pH, via unknown mechanism involving ¹O₂, H₂O₂ and HO^.. The pathways connecting the experimentally suggested components are shown with solid arrows. Other paths lacking evidence were shown with broken arrows.