Abstract
An estimation of the tuber sink potential of several sweet potato cultivars was attempted. For this purpose we used stocks of single rooted leaves of several cultivars grafted with uniform single leaf scions of a single type of cultivar, because the source potentials i.e. leaf area and photosynthetic potential were able to be uniform and sink organs other than tuber were restricted. The source activity, i.e. leaf area and apparent photosynthetic rate, did not differ statistically among stock cultivars. However, the tuber dry weight correlated significantly with the leaf area, therefore the tuber sink potential was estimated by the tuber dry weight per unit leaf area. The apparent photosynthetic rate was regulated by mesophyll resistance of CO2 diffusion, and the mesophyll resistance was influenced by tuber sink potential through the control of leaf starch content. Thus, the matter production of grafts was largely depended on the tuber sink potential in this system. The tuber sink potential was different among stock cultivars significantly at 1%. It was higher in cv. Koganesengan and Shirosatsuma and lower in cv. Tsurusengan.
