Effects of photooxidants on plants.

Photooxidants such as ozone or hydroperoxides are potentially damaging to plants, because they can rise the intracellular amount of toxic oxygen species. Since aerobic organisms are adapted to live with the threat of oxidation, protection mechanisms exist in plant cells that can remove injurious agents in the symplastic as well as in the apoplastic space. However, when the stress applied exceeds a critical threshold of the adaption capacity of the metabolic responses, cellular injury, reduced vitality or even death of the plants may result.