中文摘要：

铅（Pb）是环境中最常见的重金属污染物,其危害性较强。植物种子萌发和幼苗生长容易受到铅的毒害。为了探究Pb对于种子萌发和其生理代谢的影响,本研究以笋王1号为材料,采用水培方法,测定不同浓度Pb胁迫下莴苣种子的发芽率、发芽势、发芽指数、活力指数及幼芽中膜脂过氧化产物丙二醛（MDA）含量、超氧化物歧化酶（SOD）、愈创木酚过氧化物酶（POD）、过氧化氢酶（CAT）活性和相对电导率的变化情况。结果表明：0.6mmol/L Pb胁迫可提高莴苣种子的发芽率,随着Pb浓度的增加（1.2～6.0 mmol/L）,莴苣种子的发芽率逐渐降低;发芽势、发芽指数和活力指数的变化趋势与发芽率基本相同,均表现出低促高抑的效应;随着Pb胁迫浓度的增加,幼芽中MDA含量、相对电导率、SOD和POD活性逐渐增加,但3.6 mmol/L的Pb则抑制SOD活性;CAT活性则随Pb浓度的增加而表现出先增加后降低。因此,氧化胁迫是Pb抑制莴苣种子萌发和幼苗生长的重要原因之一。

英文摘要：

Lead is one of the most widespread and dangerous heavy metals in the environment.It is toxic to seed germination and seedling growth.In order to explore the effects of lead on seed germination and physiological metabolism,lettuce variety Sunwang NO.1 was taken as material to investigate germination rate,germination potential,germination index,vigor index and the changes of malonaldehyde content（MDA）,superoxide dismutase（SOD） activity,peroxidase（POD） activity,catalase（CAT） activity,and relative conductivity under Pb stress by solution culture.The results showed that 0.6 mmol/L Pb could promote germination rate,however,as Pb concentration increased from 1.2 mmol/L to 6.0 mmol/L,the germination rate was decreased.The germination potential,germination index,vigor index exhibited the same change trends as germination rate being promoted at lower Pb concentration and being inhibited at higher Pb concentration.In addition,MDA content,relative conductivity and activities of SOD and POD in plumule were improved gradually with the increase of Pb concentration,but 3.6 mmol/L Pb depressed SOD activity.The activities of CAT droped at lower Pb concentrations and rose at higher Pb concentrations.The results indicated that oxidative stress contributed to the inhibion of seed germination and seedling growth of lettuce by Pb.