Glutathione is a thiol-containing tripeptide, which appears to be present in nearly all living organisms and which is involved in many important metabolic and physiological processes. The present volume focuses on the biological significance of glutathione in plants. The biochemistry and the metabolism of glutathione are reviewed, and its role in sulphur and selenium metabolism in plants is discussed. The significance of glutathione and of glutathione-related enzymes in the adaptation to natural stress, heavy metals, xenobiotics, air pollution, and in plant — pathogen and plant — animal interactions are evaluated. The main aim of this second volume in the series Plant Ecophysiology is to raise the interest of advanced students and junior researchers in the role of glutathione in plants and to supply basic and comprehensive information for scientists already working on related topics.