Today, biologists all over the world speak the same scientific language of molecular biology and use the same molecular tools. More interest and attention is given to molecular biology of abiotic stress tolerance and modes of installing better tolerant mechanisms in crop plants. These studies make plants capable of sustaining their yields even under stress conditions. Further, the information gained may form the basis for its application in biotechnology and bioinformatics. This book does not only review the current status in the physiology and molecular biology of stress tolerance and its improvement in plants but will also trigger further research on this exciting topic.