Source–Sink Relationships

Abstract Life on earth depends on the growth and survival of plants. In order for plants to grow and develop effectively, coordination between sources and sinks is required. Source organs provide a net uptake of resources whilst sink organs have a net drawdown of resources. Molecular mechanisms regulate the relationship between sources and sinks. These molecular mechanisms include carbon‐ and nitrogen‐containing metabolites, plant hormones and genes. Sources and sinks for both carbon and nitrogen are key contributors to plant growth, and these regulate themselves and one another via feedback, feedforward and crosstalk mechanisms. Our understanding of the relationships between sources and sinks is increased by experimental manipulations of the source–sink balance. To bring about increases in crop growth and yield, a holistic view of sources and sinks must be developed, including the molecular mechanisms underpinning the relationships between them. Mathematical modelling can be an effective tool for providing this unified perspective. Key Concepts Sources have net uptake of a resource and sinks have net utilisation of a resource. Plant growth is underpinned by sources and sinks. Sources and sinks for both carbon and nitrogen are vital components of plant development. Molecular mechanisms including metabolites, genes and phytohormones regulate the source–sink balance. An understanding of source:sink relationships can help improve crop yield.