Detecting stress-induced reactive oxygen species in plants under UV stress

Sunlight is the energy source for photosynthesis in all land plants and in many aquatic organisms. On the other hand, solar irradiation may also appear as a stress, specially when it is combined with other factors, such as deviations from optimal growth conditions (temperature, water status) or with environmental pollutants (heavy metals, air pollutants, acidic rain). The adaptation and acclimation of photosynthetic organisms to changing environmental conditions is important, not only for the plant's survival but also for manking utilising them as food, raw material and energy source. Reactive oxygen species (ROS, also known as active oxygen species, AOS) are associated with stress and stress response in many ways: They may appear as primary elicitors, as propagators of oxidative damage, or as by-products. More recently, ROS are also considered as messenger molecules involved in signalling pathways, thus potential inducers of defence or adaptation. Until recently, the involvement of ROS in stress was usually presumed from products of oxidative damage. These techniques are useful and important, but - unlike more direct methods-they provide little information about the primary reactions. Also, due to increasing recognition of ROS in signal transduction when they are present at low levels and do not cause much oxidative damage - methods for direct ROS detection in vivo are of special importance. After giving an overview on basic ROS chemistry, this chapter will illustrate direct and indirect methods of ROS detection with special emphasis on plants and their response to UV-B (280-320 nm) irradiation.