## 3 Discussion
The total AsA concentration detected was higher than that reported in leaves of other _Citrus_ species, such as Satsuma mandarins (\(\sim\)160 mg/100 g FW) [20], Navel (200-250 mg/100 g FW) or blood orange (\(<\)100 mg/100 g FW) [21], but comparable to that found in apple leaves (440 mg/100 g FW) [40]. Interestingly, both AsA and DHA content remained almost unaltered during leaf development, in contrast to the pattern observed in DHA concentration during petal development (Figure 2B). In leaves of other species, such as tea leaves, a similar trend in AsA content with leaf aging was found [41]. [PERSON] et al. [21] reported important seasonal changes in AsA in leaves of different orange varieties and suggested a tissue and species specificity in the regulation of AsA during development that may explain the differences found in vegetative tissues among the different _Citrus_ species. During the reproductive development of Valencia oranges, differences in AsA concentration and in the pattern of accumulation were detected between the flavedo and pulp, in agreement with previous reports [19; 20]. AsA content was higher in the flavedo than in the pulp throughout fruit development, and while it remained relatively constant in the pulp, it experienced large fluctuations in the flavedo (Figure 3C,D). A higher concentration of AsA in the flavedo has previously been reported in different _Citrus_ species [19], and also in other fruit species such as apples [13]. It has been suggested that this differential accumulation of AsA may be related to the higher exposure of the flavedo to sunshine during the growing season, as light avoidance dramatically reduced AsA biosynthesis in the flavedo of _Citrus_ fruit [23]. Moreover, as the flavedo of the fruit is more widely exposed to stress signals, it is reasonable to assume a larger demand of antioxidants to cope with these adverse conditions. Similarly, other plant antioxidants--such as carotenoids, tocopherols, and flavonoids--have been detected at higher concentrations in the flavedo than in the pulp [42; 43; 44]. Furthermore, AsA in the flavedo of Valencia oranges changed significantly during development and maturation distinguishing three phases of accumulation (Figure 3C). In the first phase of cell division and early fruit development (form June to September) AsA content declined gradually, suggesting a demand of antioxidants during this period of cell enlargement. Later on, AsA in the flavedo increased to reach a maximum around the end of the second phase (December), coincidentally with the initiation of color break. Afterwards,AsA concentration declined progressively in the flavedo of mature fully colored fruits (Figure 3B,C). Other studies have also detected a maximum of AsA concentrations in the flavedo of fruit of several _Citrus_ species during the transition from chloroplast to chromoplasts (October to November), that declined afterwards. Since Valencia Late is a late ripening orange variety with a slow rate of fruit de-greening, it is reasonable that the maximum of AsA content in the flavedo may be reached later than in other varieties, suggesting that the endogenous content of this antioxidant may be species-specific and also influenced by environmental conditions [19; 23]. By contrast, AsA concentration in the pulp drastically increased from June to July, and reached a maximum in September. Contents decreased again in October and experienced fluctuations during the remaining months of fruit development and maturation. Although DHA only accounts for a small proportion of total AsA content, concentrations increased gradually during fruit development and reached a maximum in overmature fruit. It is noteworthy the abrupt increase in AsA in the pulp of fruit in July, immediately after the physiological fruit June-drop and when the pulp started to expand and to build up its development (Figure 3D). These results clearly demonstrated a differential regulation of AsA accumulation in the flavedo and pulp of _Citrus_ fruits, as it has been reported for other metabolic processes [45].