两种浮萍植物的叶绿体超微结构对模拟酸雨的敏感性

用蒸馏水和不同pH值(5.5,4.5,3.5和2.5)的模拟酸雨培养浮萍(Lemn aminorL.)和紫萍(Spirodela polyrrihiza(L.)Schleid)48h后,测定叶状体膜系统渗漏率,观察叶绿体超微结构的变化。结果表明,随酸雨pH的下降,两种浮萍叶状体的膜系统渗率增大,叶绿体超微结构受损。浮萍和紫萍对酸雨的敏感性和伤害时细胞与叶绿体形态变化显示一定的种间差别。浮萍的结构性损伤始于pH4.5,原生质体收缩,出现质壁分离,基粒结构混乱;pH3.5时叶绿体肿胀呈球状,片层结构破坏并出现许多空泡。紫萍在pH3.5时膜系统的外渗率仍较低,基粒和基质类囊体结构无明显改变;pH2.5时叶绿体结构才出现严重伤害,但未见明显的肿胀与质壁分离现象。因此认为在两种浮萍的共生水体中,紫萍对酸雨污染有较强的生存竞争能力,而浮萍则可用作pH<4.5水体的灵敏指示植物。

The Sensitivity of Chloroplast Ultrastructure of Two Duckweed Species to Simulated Acid Rain

The membrane leakage rate and chloroplast ultrastructure were investigated in the fronds of two duckweeds, Lemna minor L. and Spirodela polyrrihiza (L.) Schleid, cultured in distilled water and in different pH values (5.5, 4.5, 3.5, 2.5) of simulated acid rain for 48 h. The membrane leakage rate and alteration of chloroplast ultrastructure in two duckweeds were enhanced with the decreasing pH value. A different sensitivity to acid rain and changing pattern of injured chloroplast morphology were found between two species. In L. minor, the damages of chloroplast and membrane system began at pH 4.5, subsequently, severe plasmolysis, circular dilated chloroplast and the confused structure of grana with numerous vesicles were observed, as pH value of acid rain was dropped down to 3.5. However, in S. polyrrihiza under pH 3.5, less membrane leakage rate (17%) was accompanied by partial break in the outer envelope of chloroplast, while the structures of grana and stroma thylakoid showed no obvious change. The evident damage of chloroplast ultrastructure in S. polyrrihiza appeared at pH 2.5, but no severe plasmolysis and chloroplast swelling were seen. It is postulated that in the freshwater body, S. polyrrihiza may exhibite a stronger ability of existence competition to acid pollution than L. minor, and L. minor may be used as a sensitive plant indicator for water body with pH value less than 4.5.