This book addresses the crucial aspects of plant adaptation strategies in higher as well as lower plant groups. Stress induced by changing environmental conditions disrupts or alter various physiological and metabolic processes in organisms, however, plants have evolved various defence strategies to cope with external perturbations. The book discusses speciation changes in response to extreme ecological conditions such as cold, heat, aridity, salinity, altitude, incidental UV radiation and high light intensity, which are particularly relevant in the current scenario of global warming. It also explores the effects of human activities and emission of phytotoxic gases. Further, it describes the overall adaptation strategies and the multifaceted mechanisms involved (integrated complex mechanism), ranging from morphological to molecular alterations, focusing on plants' capabilities to create an inner environment to survive the altered or extreme conditions. This book is a valuable tool for graduate and research students, as well as for anyone working on or interested in adaptation strategies in plants.