Introduction to optical methods in photosynthesis.

Optical spectroscopy is widely used to study structure and function of photosynthetic systems. Due to the large variety of different methods, these studies have contributed a lot to the identification of the cofactors involved in the primary reactions of photosynthesis and to the elucidation of the kinetics of the light-induced energy and electron transfer reactions. Within other aspects of photosynthesis research as e.g. photoinhibition, these techniques play an important role as well. In this brief introduction, I will focus on the basic principles of the different methods and the information obtained by applying these various techniques. In the reviews that follow, under the section "Optical Methods", these methods are discussed in detail.