Stress physiology deals with different aspect of environmental stresses, such as drought, salinity, temperature, light, heavy metals and biotic stresses in plants. Most of these functional aspect follow the same basic principles of oxidative stresses. Hence for any understanding of topics in plant physiology an emphasis on the underlying physio-biochemical principles is necessary. This book aims to follow this approach.Oxidative stresses in crops is a text book meant for B.sc, M.sc and Ph.D students. The book has 25 chapters covering drought stress effects on major antioxidant enzymes activity and some biochemical biomarkers in crops.This book is first of its kind in focusing on oxidative stress in the major crops of Iran. We hope, that, the book will be a very good resource material for crops management scientists, researchers, students.We profusely thank all the authors, who have richly contributed research papers to this very productive volume. We are proud to note, that, this book is a part of outcome of M.sc and Ph.D students of Islamic Azad University- Iran.We look forward to useful suggestions and constructive criticisms from students and researchers.