Nutrients are taken up by plant roots in a regulated manner and are then distributed around the plant according to demand. As the plant develops and matures, requirements will change and new sinks for nutrients will replace old. In the case of wheat, the developing grain replaces the canopy as the major sink. Hence, nutrient allocation is a dynamic phenomenon, achieved by nutrient recycling and linked to processes of development including senescence. The effectiveness of these processes strongly influences performance and quality, particularly grain protein and mineral nutrient content, which are important health and quality attributes of the seeds. The effective reuse of nutrients is an essential contributor to nutrient use efficiency, an important sustainability trait. Movement of nutrients is achieved by multiple large gene families encoding for transporters, each family usually specific for transporting individual substrates, but often with family members showing varied distribution and regulatory patterns. There are observed interactions between nutrients resulting in coordinated accumulation within the plant. Cycling of nutrients refers to the process of internal movements of nutrients between cells, compartments, and organs or their reuse in metabolic processes. It may also refer to processes occurring within the ecosystem including cycling in the soil and between soil and crop. In this article, emphasis is placed on initial uptake and use of nutrients by the wheat plant and the recycling and partitioning of these nutrients to grain tissues.
