Department of Plant Sciences

The physiological disorders of translucent flesh and gamboge in mangosteen fruits are known to be related to low calcium (Ca) content and imbalance of Ca, potassium (K) and boron (B). To effectively manipulate the content of these nutrients, an accumulation pattern of each nutrient in mangosteen is needed. In this study, fruit growth and seasonal changes in Ca, K, magnesium (Mg) and B content in mangosteen fruits from 32 mature trees at a commercial orchard in Chantaburi, Eastern Thailand were recorded for 13 weeks, starting one week after the fruits set. Fruit weight and diameter increased throughout this period. A strong relationship between fruit diameter and fruit weight was observed. The concentration of Ca, K, Mg and B in the fruits declined sharply during the first 5 weeks of recording before leveling off. However, the total amount of each nutrients accumulated in the fruits (including Ca) increased throughout the season reaching the maximum value at the end of fruit growth, right before harvest. Phloem appears to facilitate movement of K, Mg and B into fruits. The contribution of phloem in Ca accumulation could not be confirmed in this study, but it seems that Ca transports into the fruit for a longer period than previously reported. The continuous increase of accumulated Ca until harvest suggests that, in order to raise Ca content effectively, soil or spray application of Ca should not be limited to the early period after the fruit sets but extended to harvest.