Effects of Sunlight on the Mineral Content of Apple Fruit (Factors Affecting the Variation of Mineral Components of Apples Part VI)

Abstract

Factors affecting the variation of mineral components of apple fruit were studied. The following 9 elements were measured in apple fruit : Na, K, Mg, Ca, Fe, Mn, Cu, Zn, and P. Dwarfed ‘Sansa’ tree apples were grown in 2001 in an experimental orchard at the National Institute of Fruit Tree Science in Morioka. The effects of sunlight on the mineral content of apple fruit were investigated. A simple estimation of the sunlight exposure of apple fruit was carried out using Y-type recording film for measuring the total integrated solar radiation. Fruit insolation of 75 apples was measured from two directions (east and west) and inside and outside of the crown. The fruit weight and degrees Brix of apple fruit grown outside the crown were significantly higher than those grown inside. Significant correlations with solar radiation were observed for fruit weight and degrees Brix. Significant negative correlations with solar radiation were observed for the ash, K, Ca, Zn, fruit weight, and degrees Brix. The concentration of minerals in apple fruit grown inside was higher than in fruit grown outside of the crown. The concentration of minerals was higher in apples grown on the shade side than in apples grown on the sunny side. No significant differences in mineral concentrations were observed between fruit grown on the east and west sides. These results suggest that sunlight exposure for dwarfed trees was of equal importance as the fruiting direction for the dispersal of sunlight.