关键词: 梨, 增殖, 玻璃化, 生理生化, 超微结构

Abstract: In vitro shoots of‘Huangguan’pear（Pyrus pyrifolia Nakai）were selected as materials. Characteristics of propagation，physiology，biochemistry and ultra-structure were compared between normal and hyperhydric shoots. The results showed that proliferation ability of hyperhydric shoots was significantly lower than that of the normal shoots，the proliferated shoots derived from hyperhydric shoots were still hyperhydric and the degree of hyperdricity was increased. Compared to the normal shoots，the dry matter accumulation and starch content of hyperhydric shoots were decreased by 31.3% and 29.57% respectively，while the soluble sugar content increased by 13.92%. In addition，the contents of chlorophyll a，chlorophyll b and total chlorophyll in hyperhydric shoots were decreased by 40.16 %，43.24 % and 39.52 % respectively. Relative to normal shoots，hyperhydric shoots had higher contents of ZR，IAA，GA and the ratio of GA/IAA and ZR/IAA and significantly lower ratios of ZR/GA. Furthermore，the quality of chloroplast in hyperhydric shoots was lower than that in normal shoots，and chloroplast volume in the former was smaller than that in the latter. Moreover，the thylakoid stacked irregularly and the nucleus was deformed or missing in hyperhydric shoots. Taken together，these results suggest that the low content of carbohydrates，the disorder of endogenous hormone metabolism，the damage of photosynthetic structure，and the decrease in content of nuclear material in cells are the main features of hyperhydric shoots，which were the leading reasons for the decrease in proliferation ability of their offsprings.

Key words: pear, rapid propagation, hyperhydricity, physiological and biochemical characteristics, ultra-structure