梨外植体组培褐变与氧化酶活性和同工酶的关系

研究了金花梨和苍溪梨一年生营养枝芽和茎尖（外植体）中的多酚氧化酶（Polyphenol oxidase:PPO)和过氧化物酶（Peroxidase：POD）活性和同工酶及其组培褐变的周年变化规律。一年中金花梨外植体的POD和PPO活性最高期在4月，最低期在1月和12月；苍溪梨外植体两种氧化酶最高活性均在4月，最低活性出现时间与金花梨相似，一年中多数月份其活性高于金花梨。多数时期两个品种的PPO和PPD活性高低与其组培褐变率呈正相关。金花梨和苍溪梨外植体在4-7月POD同工酶有新酶带出现，金花梨外值体PPO同工酶在5月和6月而苍溪梨在5-7月有新带出现，其余时间金花梨外植体PPO和PPD均只有3条同工酶酶带；苍溪梨外植体PPO和PPD均只有4条同工酶酶带；苍溪梨芽褐变高低与其同工酶酶带多少有一定相关性，而金花梨却与其无明显的相关性。

PRELIMINARY STUDY ON THE RELATIONSHIP OF OXIDASES AND THEIR ISOZYMES WITH BROWNING RATE OF PEAR EXPLANTS IN TISSUE CULTURE

The yearly changes of POD (peroxidase) and PPO (polyphenol oxidase) and their isozymes in the buds and terminals on the annual shoots of Jinhua pear ( Pyrus bretschneidari Rehd) and Changxi pear ( P. pyrufolia Nakai) were monitored and their relationship with explant browning was analyzed. The highest activity of both enzymes appeared in April and the lowest activity occurred in December for Jinhua pear and in January for Cangxi pear. POD and PPO activity of both pear species was positively correlated with browning rate of their terminals and buds as explants in tissue culture in most months of the year. One or two new bands of POD isozymes occurred from April to July in both species and new bands of PPO isozymes occurred in May and June for Jinhua paer and from May to July for Changxi pear. In other months of the year, POD and PPO had only 3 isozyme bands in Jinhua pear explants and 4 bands in Cangxi pear explants. Explants of Changxi pear seemed to be associated, to a certain extent, with the number of isozyme bands of the same period, while no such association was noticed for Jinhua pear.