This book will present a contemporary understanding of plant adaptation to drought and salinity that emphasizes fundamental physiological, biochemical, developmental and genetic mechanisms, as a prelude to thoughtful analyses of the integrated regulation of these determinants. The following section of this book will examine new strategies being employed to identify and then enhance these tolerance mechanisms. Later chapters are focused on efforts to discover existing genetic variation in crop germplasm and wild relatives, and manipulate genetic variation using mutation, transgenic, and molecular marker-assisted breeding approaches. This book seeks to integrate a broad cross-section of scientific knowledge and expertise about key determinants of drought and salt stress tolerance with modern crop improvement strategies. Information presented here will be especially useful to agronomists and horticulturists, crop breeders, molecular-geneticists, and biotechnologists, and serve as an important scholarly text for post-graduate students and researchers.