Regulation of Carbohydrate Partitioning in Wheat Leaves

Extensive work over the past 15 years has examined the importance of fructose 2,6-bisphosphate (Fru-2,6-P2), an inhibitor of cytosolic FBPase, in regulating the partitioning of fixed carbon between sucrose and starch. This work has mainly been done in spinach leaves. In this plant, changes in the amounts of Fru-2,6-P2 regulate the activity of cytosolic FBPase, and under certain conditions this can regulate partitioning of fixed carbon between sucrose and starch [1]. Although this model almost certainly applies to many species other than spinach, its general applicability should not be taken for granted. In this poster I examine the significance of starch and sucrose as intermediary carbon stores in mature wheat leaves, and correlate this with measurements of Fru-2,6-P2. I have addressed this using two experimental systems. 1) What are the changes in the amounts of sucrose, starch and Fru-2,6-P2 during the normal day/night growth period. 2) How do the amounts of Fru-2,6-P2 and the fluxes into sucrose and starch vary in plants photosynthesising under different light intensities. The results suggest that although changes in Fru-2,6-P2 may regulate carbohydrate partitioning between the night and the day, the metabolite is not important in regulating partitioning when photosynthesis rates are varied by changing the light intensity. Further experiments using a wider range of experimental conditions and/or transgenic plants are required to examine in much greater detail the role of this metabolite in wheat leaves.