Tansley Review No. 27 The control of carbon partitioning in plants

Abstract

Summary: This review reports on the processes associated with carbon transfer and metabolism in leaves and growing organs and the role of long‐distance transport and vascular links in the regulation of carbon partitioning in plants. Partitioning is clearly influenced by both the supply and demand for photosynthate and is moderated by vascular connections and the storage capacity of the leaves and pathway tissues. However there appears to be little more than circumstantial evidence either that short distance transfer of carbon within either the source or the sink, or that long‐distance transport in the phloem, are limiting photosynthesis or growth directly. Although individual biochemical and physiological processes relating to photosynthesis and growth may be well understood, the factors primarily responsible for the control of carbon partitioning in plants have not been clearly identified. There is a need for a greater understanding of organ initiation and development (source and sink formation and potential size), the clear identification of whether growth is sink or source limited (including possible sink‐controlled photosynthesis) and a detailed assessment of the role of storage in buffering developmental and environmental changes in sink and source activity. Also more information is needed on the role of hormonal and nutritional factors in regulating source and sink activity (organ interactions not directly associated with carbon transfer). CONTENTSSummary341I.Introduction342II.General source‐sink relationships342III.Control at the source345IV.The utilization of photosynthate: sink characteristics and limitations353V.Vascular constraints and temporary storage360VI.Concluding comments366Acknowledgements366References367