不同土壤水分条件下铅胁迫对白羊草种子和幼苗的影响

针对我国西北地区铅锌矿区存在的干旱和铅污染交互胁迫的情况，以白羊草（Bothriochloa ischaemum）为研究对象，通过试验模拟方法分析不同土壤水分条件下铅胁迫对白羊草种子发芽率、发芽势以及幼苗根长、苗长、超氧化物歧化酶（SOD）活性、过氧化物酶（POD）活性、过氧化氢酶（CAT）活性和丙二醛（MDA）含量的影响。结果表明：单一的土壤水分条件和铅胁迫处理对白羊草种子萌发和幼苗生长均存在抑制作用，发芽率、根长和苗长的抑制效应顺序为根长 >苗长 >发芽率。水分和铅交互胁迫对白羊草SOD、POD和CAT活性的影响规律不明显，表现出一定的协同或拮抗效应；而MDA含量与对照组相比则显著增加（P<0.05），表明交互胁迫对白羊草生物膜系统造成了一定的伤害。综合分析说明，白羊草对水分和铅交互胁迫具有一定的耐受性（土壤相对含水量70%，铅含量700 mg·L^-1的条件下仍能存活并生长），而且适当的交互胁迫（土壤相对含水量92.6%，铅含量100 mg·L^-1）可以促进白羊草种子的萌发和幼苗的生长。因此，白羊草可以作为西北地区铅锌矿区生态系统修复的先锋草本植物。

Effects of Lead Stress on Seed and Seedling of Bothriochloa ischaemum under Different Soil Moisture

For the case of interactive stress of drought and lead on the lead-zinc mining district of northwestern China, the objective of this experiment was to study changes in the seed germination rates, germination potentials, root length, germ length, POD, SOD, CAT activity and MDA content of Bothriochloa ischaemum under lead stress with different soil moisture. The results showed that only soil moisture or only Pb stress had inhibition effect on the seed and seedling of B. ischaemum. The inhibition orders were root length >germ length >germination rates. The combination of drought and Pb stress had less effect than only soil moisture or Pb stress on POD, SOD and CAT activity in B. ischaemum, and it had either synergistic or antagonistic effect depending on the conditions. However, the MDA content increased significantly than the control treatment, it indicated that the interactive effect of drought and lead stress caused some damage to the biofilm system of B. ischaemum. In summary, B. ischaemum was resistant to the combined effects of Pb and moisture (it still survived in the condition of 70% of soil water content and 700 mg·L^-1 Pb). Appropriate combined effects (92.6% of soil water content and 100 mg·L^-1 Pb) promoted seed germination and seedling growth of B. ischaemum. So B. ischaemum could be used as pioneer herb to repair the lead-zinc mining district of northwestern China.