[Relationship between ascorbic acid accumulation and related enzyme activities in fruit of Rosa roxburghii Tratt]

Ascorbic acid (AsA) and sugar levels, together with activities of L-galactono-1,4-lactone dehydrogenase (GalLDH, a key enzyme in AsA biosynthesis in higher plant), AAO, AAP, MDAR and DHAR in fruit of Rosa roxburghii Tratt were measured during development. The result showed that AsA accumulated continually but with a slow, fast and slow accumulating rate in the R. roxburghii fruit during its development, in which the period from the end of June to the early of August was the most important period of AsA accumulation, since the AsA accumulated in this stage accounting for approximately 90% of the final level (Fig.1B). Changes in GalLDH activity coincided with AsA accumulating rate during fruit development (Fig.2B). The extremely significant positive correlation existed between the GalLDH activity and AsA accumulating rate (r(2)=0.783**) (Fig.3). Transitory and low activities of AAO and AAP in the fruit were detected in the initial stage of development (Table 1), suggesting that little AsA degraded by the activities of the two oxidative enzymes during the whole development. This data elucidated, at least in part, the reason for high accumulation of AsA in the R. roxburghii fruit. Furthermore, no activity of MDAR or DHAR in the fruit was detected during the whole development, implying that the two enzymes are not key factors for contribution of AsA level. No correlation was found between AsA content and sugar contents in the R. roxburghii fruit.