不同浓度Pb(Ⅱ)对稀脉萍和紫萍的毒性效应

Toxicity Action of Pb(II)with Different Concentrations on Lemma aequinoctialis and Spirodela polyrrhiza

浮萍类植物(以下简称浮萍)具有繁殖快、用途广泛、综合利用率高等优良特性,可应用于水生生态毒理学的研究。选择我国浮萍中分布最广的两个种类,即稀脉萍(Lemma aequinoctialis)和紫萍(Spirodelapolyrrhiza)作为植物材料,选择Pb(Ⅱ)作为实验重金属,探讨不同浓度Pb(Ⅱ)对这2种浮萍的毒性影响。结果表明:(1)随着Pb(Ⅱ)浓度的提高,稀脉萍和紫萍的生长都受到显著抑制;(2)Pb(Ⅱ)对稀脉萍和紫萍叶绿素的产生都有抑制的作用,但稀脉萍的叶绿素含量的变化幅度较大,当Pb(Ⅱ)浓度为30mg/L,经4d处理后稀脉萍和紫萍的Chl.a、Chl.b和Chl(.a+b)分别比其对照降低了39%、42%、40%和13%、33%、21%。当Pb(Ⅱ)浓度为1～15mg/L时,两种浮萍叶绿素a和叶绿素b之间的比值均随着重金属浓度梯度的升高而降低。(3)经4d处理,稀脉萍和紫萍的可溶性蛋白含量分别比其对照降低了32%和30%。(4)经4d处理,稀脉萍的POD活性在Pb(Ⅱ)浓度为20mg/L时达到峰值,而紫萍在本实验Pb(Ⅱ)浓度设置范围内未有峰值,且最大值相比较分别高出其对照41%和100%。稀脉萍和紫萍可用作Pb(Ⅱ)对水生植物的毒性效应监测,采用生长情况、叶绿素含量等作为监测指标,而稀脉萍对Pb(Ⅱ)胁迫更为敏感。

Duckweed plants with properties of fast breeding, wide range of uses and comprehensive utilization can be used for the study of aquatic ecotoxicology. Two types of duckweed that widely distributed in China including Lemma aequinoctialis and Spirodela polyrrhiza were chosen as plant materials, and Pb （Ⅱ） as a pilot metal to evaluate the toxicity action of Pb （Ⅱ） of different concentrations on the duckweed. Results showed that growth of Lemma aequinoctialis and Spirodela polyrrhiza was significantly inhibited with increasing concentration of Pb （Ⅱ）. Formation of chlorophyll in Lemma aequinoctialis and Spirodela polyrrhiza were inhibited by Pb （ Ⅱ ）. However, the chlorophyll content of Spirodela polyrrhiza changed more widely. When the concentration of Pb（ Ⅱ ） was 1-15mg/L, the ratio between ChL a and ChL b in both duckweeds, decreased with the rise of heavy metal concentration gradient. Treatment after 4d, the soluble protein contents of Lemma aequinoctialis and Spirodela polyrrhiza were 32% and 30% lower than the control group respectively, and the activity of POD in Lemma aequinoctialis reached a peak when the concentration of Pb （ Ⅱ ） was 20mg/L, but Spirodela polyrrhiza had no peak in the experiment. The activity of POD in Lemma aequinoctialis and Spirodela polyrrhiza was respectively 41% and 100%, higher than the control group. Lemma aequinoctialis and Spirodela polyrrhiza may serve as toxicity monitoring of aquatic plants with chlorophyll content as monitoring index.