ABSTRACT
Photosynthesis drives carbon (C) and nitrogen (N) assimilation by the provision of assimilatory power (reduced ferredoxin, NADPH, ATP). The assimilation of N requires not only energy but also C skeletons (Figure 6.1). These are provided by C metabolism; triose phosphate produced as a result of photosynthetic C assimilation in the leaves can either be used to make carbohydrates (mainly sucrose and starch) or it can be directed through the anapleurotic pathway to provide skeletons for N assimilation. Sucrose exported from the leaves provides the energy and C skeletons to drive N assimilation in the roots and associated tissues. C assimilation, C partitioning and N assimilation are highly co-ordinated and there are many points of reciprocal control (Foyer et al., 1994a, 1996).
