Studies On Dormant Characteristic And Releases From Dormancy Of Pear

North deciduous fruit trees evolved into biomechanism of dormancy for a long time to adapte to environmental and climatical changes in winter. The physiological and biochemical metabolisms did not stop, but even were inactivited. Some pear cultivars including 'Qiyuesu' , ' Starkrimson' and ' Packham'sTriumph' were selected as material in this experiment to study systemically effects of temperature daily cycle treatment on the accumulation of chilling requirment and the opening of flower buds. Studying the effect of different material of breaking dormancy and different low temperature to break pear bud dormancy;analysing the physiological and biochemistry changes of dormant and treated by KNO₃, KNO₃+H₂NCSNH₂, GA+6-BA, low temperature buds and shoots. The main results were as follow:1 .The apricot floral buds had different chilling requirements significantly between different cultivars. Qiyuesu possessed the lowest chilling requirements: Packham'sTriumph was the highest: Starkrimson was between the former two cultivars.This experiment indicated that 0⁷.2℃ chilling unit was the same as Utah models in measuring the chilling requirement.2 .SOD activity was always lower, then experienced a little peak;POD activity rose all the time during the whole dormancy period. With chilling requirement increasing, O₂content rose constantly. MDA content was higher in the former period of dormancy, and MDA content descend constantly in the later period. Shoots together with buds tendency unanimously yet shoots the tendency either is similar than buds ahead of time during the dormancy period.3 .The carbohydrate content experienced jump-change, starch and soluble sugar had the contradict changes trends during the whole dormancy period, during dormancy release the protein content fell down sharply and the free amino acid content rose sharply .The jump-change stage of the former four index were consistent with the dormancy . Shoots together with buds tendency unanimously yet shoots the tendency either is similar than buds ahead of time during the dormancy period.4 .KNO₃ treatment and KNO3+H2NCSNH2 treatment all accelerated floral dormancy broken dramatically. The different concentration had different effects in breaking pear bud dormancy: 6% KNO₃+2 % H₂NCSNH₂treatment had the best effect which had the highest bud germination. KNO₃+H₂NCSNH₂treatment had better effect than KNO₃ treatment.5 .GA+6-BA treatment and 6-BA treatment all accelerated floral dormancy broken dramatically. The different concentration had different effects in breaking pear bud dormancy: 120mg.L^-1 GA₃+100 mg.L^-16-BA treatment had the best effect which had the highest bud germination. GA+6-BA treatment had better effect than 6-BA treatment.6 . The different low temperatures had different effects in breaking pear bud dormancy: 6°C treatmenthad the best effect which had the highest bud germination and needed the least chilling hours to break bud dormancy, the effect of 6°C/15°Ctreatrnent was lower than the former, 4°C and 10°C treatments had the lowest effects.