Temperatures Inhibiting Endodormancy Completion in Japanese Pear Flower Buds

Abstract

The eifects of high temperature and subzero temperature on endodormancy completion in flower buds of Japanese pear (Pyrus pyrifolia Nakai cv. 'Kosui') were investigated using potted trees. The trees were chilled in temperature-controlled (daily cycles of 6/6°C, 6/-3°C, 6/- 6°C, 18/6°C, 21/6°C and 24/6°C) dark rooms from late October or from early November. After chilling for various lengths of time, they were forced in a growth chamber adjusted to 25°C. The endodormancy completion was judged from the percentage of flowering and normal flower after forcing. Flower buds were released from endodormancy by exposure to 6°C for about 780 hours. It was clear that chilling efficiency at - 3°C fell within the range of 1/2-1/3 of that at 6°C, while at - 6°C, the endodormancy was not complete. High temperatures of 21°C or 24°C negated a part of the cumulative effect previously received from the chilling treatment, but 18°C did not negate it. © 2003, The Society of Agricultural Meteorology of Japan. All rights reserved.