摘要
用示差扫描量热计测定了菜豆第一片真叶在衰老过程中叶绿体被膜相变温度与叶绿体总脂熔融温度的变化。15日龄成长叶片叶绿体被膜相变温度为-6.7～-3.6℃,当转向衰老后,在22,29和35日龄时的相变温度分别为3.2～8.8℃、18.7～24.1℃和27.3～37.8℃。叶绿体总脂的熔融温度在15至35日龄期间也逐渐升高,但升高幅度小于被膜相变温度的升高幅度。可是,叶绿体总脂熔融温度范围却大于相应时期被膜相变温度范围。蛋白质含量下降趋势发生在叶片15日龄前,而叶绿素含量下降趋势开始于叶片21日龄之后。
Differential scanning calometry analysis of chloroplast envelope membranes from primary true leaves of Phaseolus vulgaris showed that parts of the lipid became crystalline with leaf senescence. For the 15 d leaves, the transition temperature region was -6.7～3.6℃, indicating that at physiological temperature the liquid-crystalline lipids of chloroplast envelope membranes played a dominant rule. On the 22nd day, the transition temperature region rose to 3.2～8.8℃, indicating that the gel phase lipid appeared markedly in the envelope membranes. The transition temperature approached the physiological temperature on the 29th day after leaf appearing, and went beyond it on the 35th day after leaf appearance. The melting temperature of total lipid extracts from the whole chloroplast continued to rise with the development of senescence, but its rate of increase was less than that of transistion temperature for envelope membranes. It showed that there were changes in phase transition behavior of chloroplast envelope membranes during leaf senescence. The appearance at physiological temperature of gel phase lipid in chloroplast envelope membranes coincided temporally with the initiation of decline in chlorophyll content on the 21st day, but the clear appearance of crystalline characteristics in chloroplast envelope membranes lagged behind the loss of total protein. Therefore, the initiation of leaf senescence couldn't be attributed to the changes in phase transition behavior of chloroplast envelope membranes.
关键词
菜豆
叶片
衰老
叶绿体被膜
Phaseolus leaves, senescence, phase transition temperature, chloroplast envelope membrane, melting temperature of total lipid
