Adopting an interdisciplinary approach to the study of photoassimilate partitioning and source-sink relationhips, this work details the major aspects of source-sink physiology and metabolism, the integration of individual components and photoassimilate partitioning, and the whole plant source-sink relationships in 16 agriculturally important crops. The work examines in detail the components of carbon partitioning, such as ecology, photosynthesis, loading, transport and anatomy, and discusses the impact of genetic, environmental and agrotechnical factors on the parts of whole plant source-link physiology.