ABSTRACT
Photoreactions generally bear the potential for the generation of reactive oxygen species (ROS). This chapter will provide an introduction into the current understanding of plant defense processes in response to accumulating photosensitizing tetrapyrroles. The photodynamic consequences of chemically induced or hereditary accumulation of photoreactive tetrapyrroles by the modification of their metabolic pathway have previously been described and have stimulated the development of strategies to benefit from the photodestructive capacity of tetrapyrroles in agriculture and plant biotechnology as well as in medicine.
