DOI: 10.1093/jxb/erg037 Balancing supply and demand: the spatial regulation of carbon metabolism in grass and cereal leaves

Leaf primary metabolism responds to changes in both supply of inputs and demand for products. Metabolic control in leaves changes both spatially and tem-porally. Using leaves of C3 temperate Gramineae, the spatial control of carbohydrate metabolism has been studied using a range of approaches. Single-cell sampling and subsequent analysis of metabolites, proteins and transcripts has indicated signi®cant dif-ferences between epidermal, mesophyll and paren-chymatous bundle sheath cells. These differences correlate with differentiated function as heterotrophic, autotrophic and transport pathway components of the leaf. The review emphasizes the key role of sucrose and discusses its catabolism to hexoses and its anabolism to fructans as mechanisms for the pre-servation of sucrose gradients within the leaf