This book provides an up-to-date overview of redox signaling in plant cells and its key role in responses to different stresses. The chapters, which are original works or reviews, focus on redox signaling states; cellular tolerance under different biotic and abiotic stresses; cellular redox homeostasis as a central modulator; redox homeostasis and reactive oxygen species (ROS); redox balance in chloroplasts and mitochondria; oxidative stress and its role in peroxisome homeostasis; glutathione-related enzyme systems and metabolism under metal stress; and abiotic stress-induced redox changes and programmed cell death. The book is an invaluable source of information for plant scientists and students interested in redox state chemistry and cellular tolerance in plants.