Abstract: In order to research the response and tolerance of Poa pratensis to lead stress,a pot experiment was conducted to study the effect of different concentrations of Pb(NO₃)₂(0,100,200,300,400,500 and 600 mg·L^-1) on seed germination and physiological characters of Poa pratensis,respectively. The results showed that,at the germination stage,the germination rate and plumule length increased firstly and then decreased with the increase of Pb²⁺ concentration. The germination energy,germination index,vigor index,root length and seedling weight decreased gradually with the increase of Pb²⁺ concentration. At seedling stage,the content of chlorophyll had no significant change when Pb²⁺ concentration was less than 200 mg·L^-1,while it was significantly lower than control when Pb²⁺ concentration was more than 400 mg·L^-1. The relative permeability of cell membrane,the contents of Malondialdehyde (MDA) and Proline (Pro) increased with the increase of Pb²⁺ concentration. And the activities of protective enzymes and reactive oxygen free radicals first increased and then decreased with increase of Pb²⁺ concentration. The results indicated that less than 200 mg·L^-1 lead stress could promote the germination,while more than 300 mg·L^-1 could significantly inhibit the germination of Poa pratensis seeds. In order to resist the injury of Pb²⁺ stress,Poa pratensis seedlings could inhibit the increase of relative permeability of cell membrane,the content MDA and reactive oxygen free radicals,by activating its antioxidant enzyme system and increasing the content of Pro when the concentration of Pb²⁺ was less than 400 mg·L^-1. However,the normal growth of Poa pratensis would be affected when Pb²⁺ concentration was more than 400 mg·L^-1. It can be seen that Poa pratensis could be planted to beautify the environment in areas where lead concentration was less than 300 mg·L^-1.

Key words: Poa pratensis, Lead stress, Germination stage, Seedling stage, Physiology and biochemistry

摘要： 为研究草地早熟禾（Poa pratensis）对铅（Pb）的适应性，本研究采用盆栽试验分析了铅胁迫（Pb²⁺浓度为0，100，200，300，400，500，600 mg·L^-1）下草地早熟禾种子的萌发情况和幼苗生理生化的变化，结果显示：萌发期，随着Pb²⁺浓度的增加，发芽率和芽苗的芽长先升高后降低；发芽势、发芽指数、活力指数、芽苗的根长和苗重均随着Pb²⁺浓度的增加而逐渐降低；幼苗期，叶绿素含量在Pb²⁺浓度小于200 mg·L^-1时无明显变化，在Pb²⁺浓度大于400 mg·L^-1时显著低于对照；细胞膜相对透性、丙二醛（Malondialdehyde，MDA）和脯氨酸（Proline，Pro）含量均随着Pb²⁺浓度的增加而升高，保护酶活性和活性氧自由基均随着Pb²⁺浓度增加先升高后降低。试验结果表明浓度小于200 mg·L^-1的铅胁迫可促进草地早熟禾种子的发芽，大于300 mg·L^-1则显著抑制；苗期在Pb²⁺浓度小于400 mg·L^-1时草地早熟禾可通过激活自身的抗氧化酶系统和增加Pro含量抑制细胞膜相对透性、MDA和活性氧自由基的增加以适应Pb²⁺胁迫，大于400 mg·L^-1时则影响其正常生长，可见土壤中铅浓度小于300 mg·L^-1的铅污染地区可种植草地早熟禾绿化环境。

关键词: 草地早熟禾, 铅胁迫, 萌发期, 苗期, 生理生化