Sugar and Ascorbic Acid Contents of Satsuma Mandarin Fruits Harvested from Exterior and Interior Canopy of Trees during Fruit Development

Sugar and ascorbic acid (AsA) contents in juice were investigated in satsuma mandarin (Citrus unshiu Marc. cv. Hayashi) fruits picked from exterior and interior canopy of 21-year-old trees during fruit development, to elucidate the effect of light intensity on fruit quality.1. The fruit from exterior canopy was superior in diameter, weight, peel color (a/bvalue) and soluble solids content, but inferior in titratable acid content to the fruit from interior canopy.2. The content of sugars in juice, which were detected as glucose, fructose and sucrose, was higher in exterior fruits throughout growing period than in interior fruits. The difference in sugar content (g/100ml of juice) between the fruits from the two positions of canopy remained nearly constant during the sampling period, whereas difference in sugar content in a fruit (g/juice of one fruit) tended to increase during the period.3. The fruits from exterior canopy contained higher AsA in juice than the interior canopy fruits, and the difference in AsA content (mg/100ml of juice) between the two positions was nearly the same throughout fruit development. On the other hand, the difference in AsA content in a fruit (mg/juice of one fruit) between the two increased as growth advanced.4. A significant correlation was found between contents of sugars (g/juice of one fruit) and of AsA (mg/juice of one fruit) in a fruit. In all cases, the coefficient of correlation was found to be 0.98**.5. The contents of sucrose and AsA in the juice of fruits at maturation stage were decreased by shading treatment during fruit growth.