Light-exposure of sprouting tubers of both sweet potato and yam bean caused "greening" in the periderm; however, the light-induced inhibition of tuber growth observed in sweet potato was not observed in yam bean tubers. Examination of the protein profiles and isoperoxidase banding patterns revealed no significant differences between lightexposed and dark-grown tuber tissue. While the basis of this lightmediated effect on starch accumulation may not be easily determined within the limits of biochemical assays, it has now become possible, with the emerging new molecular techniques, to determine whether this phenomc.non is due to the differential expression of the genes coding for the enzymes responsible for starch biosynthesis viz A(U)DP glucose pyrophosphorylase and starch synthase. The paper highlights the further advantages of using molecular approaches to the understanding of the tuberisation process.