Seasonal trends of soluble sugar fractions in satsuma mandarin peels from August to December were investigated in relation to fruit development and peel puffing.
1. In the flavedo tissue, concentrations of sucrose as well as total and reducing sugars were relatively low from August to early September, followed by a rapid increase in October. At the harvest time, they were 22.7 per cent for reducing sugars, 11.4 per cent for non-reducing sugars and 34.1 per cent for total sugars, when expressed on a dry weight basis. The amount of non-reducing sugars augmented to a maximum in mid November and declined thereafter. On the other hand, soluble sugar concentrations of albedo tissues were 19.3 per cent for reducing sugars, 7.5 per cent for non-reducing sugars and 26.8 per cent for total sugars.
As for the seasonal change in sugar content, there existed a certain similarity between flavedo and albedo tissues. The onset of sugar accumulation, however, was one or two months earlier in the albedo than in the flavedo. In the albedo tissues, the sugars gradually increased to a maximum in November.
2. The beginning of sugar accumulation in Wase Satsuma peel was earliest, followed by Ikeda Satsuma and then by Natsudaidai and Iyo. A decline in sucrose content was observed at harvest time in all the varieties except Wase Satsuma.
3. Based on the results of qualitative tests performed by gas-liquid chromatogra- phy, it was concluded that in the Ikeda Satsuma peel, reducing sugars consisted mainly of fructose and glucose whereas non-reducing sugars consisted principally of sucrose. Among these three sugars, any considerable differences in per cent of dry weight were not observed until mid November. At the harvest time, however, the sucrose content became lowest, glucose intermediate, and fructose highest in the flavedo tissues.
4. The sugar contents of flavedo and albedo were both higher in puffy than in non-puffy fruit. Sugars were contained more abundantly in the tissue of stem end than in that of either stylar or equatorial portion.
Japanese Society for Horticultural Science