We briefly review the metabolism of the chloroplast stroma, and describe the structural modelling technique of elementary modes analysis. The technique is applied to a model of chloroplast metabolism to investigate viable pathways in the light, in the dark, and in the dark with the addition of sedoheptulose-1,7-bisphosphatase (nor-mally inactive in the dark). The results of the analysis show that it is possible for starch degradation to enhance photosynthetic triose phosphate export in the light, but the reactions of the Calvin cycle alone are not capable of providing a sustainable flux from starch to triose phos-phate in the dark. .
