This is the first volume to provide comprehensive coverage of the biology of water use efficiency at molecular, cellular, whole plant and community levels. While several works have included the phenomenon of water use efficiency, and others have concentrated on an agronomic framework, this book represents the first detailed treatment with a biological focus. The volume sets out the definitions applicable to water use efficiency, the fundamental physiology and biochemistry governing the efficiency of carbon vs water loss, the environmental regulation of this process and the detailed physiological basis by which the plant exerts control over such efficiency. It is aimed at researchers and professionals in plant physiology, biochemistry, molecular biology, developmental biology and agriculture. It will also inform those involved in formulating research and development policy in this topic around the world.