ISHS Acta Horticulturae 587: International Symposium on Asian Pears, Commemorating the 100th Anniversary of Nijisseiki Pear
EFFECT OF INTERMITTENT WARM PERIODS ON BUD BREAK AND CARBOHYDRATE CONTENTS OF JAPANESE PEAR (PYRUS PYRIFOLIA NAKAI) AT DIFFERENT ENDODORMANCY STAGES |
| Authors: | H. Honjo, Y. Kobayashi, M. Watanabe, R. Fukui, T. Sugiura |
| Keywords: | dormancy break, fructose, heating degree-hours, heat unit, glucose, starch |
| Abstract:
This study was conducted to evaluate the effect of intermittent warm periods on bud break and carbohydrate contents of Japanese pear at different endodormancy stages. Japanese pear ‘Choujuurou’ shoots with flower buds were collected on November 15 (100hrs, chilling hours below 7.2°C), December 6 (400hrs), December 24, 1999 (700hrs), and January 19, 2000 (1000hrs). High temperature treatments were performed outdoors using a small transparent chamber. The heating degree-hours (heat unit, °Chr) was calculated as an hourly summation of temperatures above 25°C. Despite accumulation of chilling hours before high temperature treatment, intermittent warm periods increased bud break with increasing heat units. The onset of bud break was also forced with increasing heat units. For the December 6 sampling, the bud break with heat unit 800°Chrs was observed in about 50 percent of the total buds (no significant increase in heat unit 0°Chr) within 15 days after sampling, and the broken buds flowered on January 7 and thereafter. High temperature accumulation after 400 chilling hrs stimulated flowering with increasing heat units. For the treatment on 400 and 1000 chilling hours, glucose, fructose and starch contents increased during high temperature treatment. After 7 days of forcing at 20°C, glucose and fructose contents decreased, but starch content continued to increase. | |
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