Relationship Between Ascorbic Acid Content and the Enzyme Activities Involved in AsA Metabolism of Potato

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,i.e. 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 stems was 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 leaves might result from higher activites of GalLDH and DHAR,while AsA accumulation in tuber might be attributed to the transportation from leaves,and DHA recycling via DHAR.