Figure 3.
Most important sources of ROS in plant cells. Singlet oxygen (1O2) may originate from excited triplet chlorophylls (Chl) that activate ground-state O2 in the photosystem II (PSII) reaction center. In PSI, superoxide and hydrogen peroxide can be produced by reducing O2. In the mitochondrial electron transport chain, complexes CI, CII, and CIII are ROS-generating systems. AltDH, alternative dehydrogenase; AOX, alternative oxidase; cyt. c, cytochrome c; CI-V, mitochondrial complex I–V; PGA, phosphoglycerate; PS, photosystem; PRX, peroxidase; RBOH, respiratory burst oxidase homologs; RuBP, ribulose 1,5-bisphosphate; Sugar-P, sugar–phosphate; TCA, tricarboxylic acid. Modified from [62].