Changes of the pedicel structure and Ca, Mg, K levels during apple fruitlet development

The physiological fruit-drop is an important portion of the yield production in apple. This experiment was performed with Fuji and Golden Delicious apple trees to investigate the relationships among the fruit development, levels of Ca, Mg and K, pedicel structure of various position in same flower cluster and the physiological fruit-drop. The results showed that the weight and Ca, Mg, K content of single fruitlet increased with the fruit development. Among various fruit-growing positions, compared with the abnormal lateral fruitlets, the normal central and lateral fruitlets had higher fresh weight, dry weight and total Ca, Mg, K content of single fruit, and bigger diameter, more vascular bundles, thicker xylem and bigger phloem vascular bundles area of pedicel,but lower content of Ca, Mg in pedicels. The correlation analysis indicated that the apple fruitlet weight was significantly positively correlated with the total Ca, Mg, K content of single fruitlet,and also with the diameter, number of vascular bundles, xylem thickness and phloem vascular bundles area of pedicel. It is suggested that the fruitlet development was closely related to the uptake of Ca, Mg, K and pedicel structure. The lower rate of uptake for Ca, Mg, K and abnormal development of pedicel mould be an important factor of apple fruit-drop.