Zn^(2+)在菹草叶片中的积累及其植物毒理学效应

Zinc Accumulation and Its Effects on Physiological Dynamics and Calcium Distribution in Submerged Macrophyte,Potamogeton crispus L.

以广泛分布的沉水植物———菹草为研究对象,通过添加不同浓度Zn2+(0、5、10、15和20 mg.L-1)的10%Hoagland营养液培养7 d,分析Zn2+在水生植物中的积累及其诱导产生的毒理学作用。结果发现:随着培养液中Zn2+浓度的增加,(1)菹草叶片中Zn2+含量极显著上升。(2)Zn2+处理使菹草产生明显的矿质营养失衡症状,主要表现为显著增加了对Fe2+的吸收和降低了对P5+和Na+的吸收。(3)光合色素中,叶绿素a和b、类胡萝卜素先升后降,分别在5、5和10 mg.L-1处理浓度时最多;叶绿素a/b一直下降。(4)GSH含量在5 mg.L-1时达到峰值后减少,而AsA则为逐渐降低。(5)各处理浓度都使ATP和可溶性蛋白含量明显减少。(6)电镜观察发现,正常条件下Ca2+主要分布在胞间隙和液泡中,细胞基质中较少;添加Zn2+后,胞间隙和液泡中的Ca2+逐渐进入细胞质,使细胞质中Ca2+浓度明显升高,在质膜内侧、细胞核和叶绿体中都出现大量呈圆环状的黑色钙颗粒。综合分析认为,AsA对Zn2+胁迫反应最敏感,Zn2+对菹草产生毒害的临界浓度为5~10 mg.L-1。

Potamogeton crispus L.exposed to elevated concentrations of zinc（up to 20 mg·L-1） for 7 d were analyzed with reference to the accumulation of metal and its influence on mineral nutrients,photosynthetic pigments,non-enzymatic antioxidants（GSH and AsA）,adenosine triphosphate（ATP）,protein content and calcium distribution.It was found that,with the rise of the Zn2＋ concentration in culture medium,（1）The accumulation of Zn2＋ was increased in a concentration dependent manner.（2）Zn2＋ resulted in imbalance of nutrient elements,and promoted the adsorption of Fe2＋ and prohibited those of P5＋ and Na＋ significantly.（3）Chlorophyll a,b and Car contents reached the highest point at 5,5,10 mg·L-1 and followed by a decline,respectively.Chlorophyll a/b showed a decreasing trend.（4）A significant reduction in AsA content was observed in Zn2＋ treated P.crispus,in contrast,an minor increase was noted in level of GSH at 5 mg·L-1 dose.（5）Soluble protein and ATP contents were found to be decreased at all Zn2＋ concentrations.（6）Electron microscope observation revealed that Ca2＋ mainly distributed within intercellular space and vacuole,some calcium deposits could be randomly found in cytoplasmic matrix under normal conditions.When different dose of Zn2＋ was added into the culture solution,the calcium level in these compartments lowered while that in cytoplasm increased remarkably,especially bigger particles of calcium deposits appeared at the inner aspect of plasmalemma.In general,AsA was most sensitive to Zn2＋ stress and the threshold of toxicity ranged from 5～10 mg·L-1.