EFFECT OF INTERRUPTION OF CHILLING ON BUD BREAK IN JAPANESE PEAR

摘要

Excised 'Nijisseiki' pear shoots were kept at 0°, 5°, 10°, 15° and 20°C for 0, 200, 400, 600, 800, 1000, 1200, 1400 and 1600 hr.and the depth of rest in leaf buds was examined. On shoots that sere exposed at 5°C, the rest of leaf buds was brokenafter 1400 hr. After 1600 hr percent bud break were 62 at 0°; 94 at 5°; 44 at 10°; 30 at 15° and 18 at 20°. 'Nijisseiki' pear shoots that had been chilled at 5°C for 200, 400 and 800 hr were then exposed at 20°C for 200 hr. After exposure at 20°C, these shoots were kept again at 5°C and depth of leaf bud rest was determined every 200 hours after re-chilling. Leaf buds on shoots which had been exposed at 20°C for 200hr in their deepest rest phase showed the saie level of hud break as the continuous 5°C treatment; bud break on shoots that had been exposed at 20°C in the decreasing rest phase were delayed in comparison with the continuous 5°C treatment.