EFFECTS OF SPUR DEFOLIATION AND GIRDLING ON FRUIT-GROWTH, FRUIT-QUALITY, AND LEAF AND SHOOT CARBOHYDRATE-LEVELS ON THE SPURS OF DIFFERENT AGES IN NIJISSEIKI PEAR

Defoliation and girdling were performed on spurs of different ages of 'Nijisseiki' pears (Pyrus pyrifolia Nakai) 10 days after anthesis, and the effects on fruit growth and quality, carbohydrate levels of leave s and shoots on the spurs were determined. Girdling resulted in the re duction of fruit size and fresh weight on 1-and 3-year-old spurs at ha rvest, but did not affect fruit growth, final size, and fresh weight o n 5- and 7-year-old spurs. Complete spur leaf removal (100% LR) had li ttle effect on fruit development on 1-year-old spurs during the whole growing season, but significantly retarded fruit development and decre ased the final size of fruit on spurs over 3 years old. This treatment also increased flesh firmness, soluble solids and pH of fruit on spur s over 3 years old which may be related to the decreased fruit size. P resence of bourse shoot and 50% LR treatment had little effect on the final size of fruit on the spurs of different ages. Our results indica te that spur leaves play a more significant role in fruit growth and d evelopment as the spur age increases. The growth and development of fr uit on a I-year-old spur depends to a great extent, on the leaves exte rnal to the spur complex; whereas fruits on 5- year-old spurs or older depend on their own spur leaves under normal conditions. On 3-year-ol d spurs, the fruit is nourished by its spur leaves and leaves outside the spur. Spur leaves seem to have an important role in the accumulati on of carbohydrates in the spur, especially in the older parts of the spur shoot.