Abstract: To investigate the relationship between ascorbate (AsA ) distribution and the activities of enzymes involved in AsA metabolism, the AsA and dehydroascorbate (DHA) contents and the activities of six related enzymes were studied in various organs of potato, i1e. young leaves, mature leaves, aged leaves, stems and tubers. The results showed that AsA was accumulated in young leaves and tubers. AsA pool size (the sum of AsA and DHA) in leaves and stemswas correlated with L-galactono-1, 4-lactone dehydrogenase (GalLDH) activity. AsA content was significantly related with the dehydroascorbate reductase (DHAR ) activity in all organs, especially in tubers. Meanwhile, DHA content was significantly associated with ascorbate peroxidase (APX) activity. This suggested that high AsA content in young leavesmight result from higher activites of GalLDH and DHAR, while AsA accumulation in tubermight be attributed to the transportation from leaves, and DHA recycling via DHAR.

Key words: potato, ascorbate, L-galactono-1, 4-lactone dehydrogenase, dehydroascorbate reductase, ascorbate peroxidase