冬季农田杂草荠菜对铅的生理响应及积累特性研究

为寻找新的铅超富集植物以弥补目前国内铅超富集植物的不足,通过盆栽试验,研究了荠菜Capsella bursa-pastoris(L.)Medic]在不同铅浓度(0、200、400、600、800、1000、1200、1400、1600 mg·kg~(-1))处理下的生长、生理及对铅的积累特性。结果表明,在所有铅处理条件下,荠菜均能正常生长,且未出现任何中毒症状。荠菜的株高、根长、叶长、叶绿素a、叶绿素b、叶绿素(a+b)、地上部与根系生物量均随土壤铅浓度的增加呈现先升高后降低的趋势,且几乎所有铅处理组的生长状况明显优于对照组。荠菜的地上部铅含量和铅积累量、根系铅含量和铅积累量、植株铅积累总量、富集系数、转运系数则随土壤铅浓度的增加而升高。在土壤铅浓度为1000 mg·kg~(-1)时,荠菜地上部、根系的铅含量分别为1 036.14、1 201.37 mg·kg~(-1),超过铅超富集植物临界值(1000 mg·kg~(-1))。地上部富集系数在土壤铅浓度高于600 mg·kg~(-1)时超过1,但转运系数均小于1。同时,荠菜的抗氧化酶活性(SOD、CAT)随土壤铅浓度的增加而升高,丙二醛(MDA)含量和活性氧自由基(H_2O_2、O_2~-)含量则处于较为稳定状态。因此,荠菜不仅有较强的铅富集能力与稳定的转运能力,而且具有较强的耐铅性,可作为一种新的铅富集植物应用于铅污染土壤修复。

Physiological responses and lead accumulation of the winter weed Capsella bursa-pastoris under lead stress

A pot experiment was conducted to examine the growth, physiological responses and lead(Pb) accumulation of Capsella bursa-pastoris(L.) Medic, a new Pb hyperaccumulator, under different Pb rates(0, 200, 400, 600, 800, 1000, 1200, 1400, and 1600 mg·kg^-1). Results showed that C. bursa-pastoris grew normally and showed no toxic symptoms under all Pb treatments. With the increase of Pb concentrations in soil, plant height, root length, leaf length, chlorophyll a, chlorophyll b, chlorophyll a+b and plant biomass all showed increases at low Pb but decreases at high Pb rates, with all higher in the treatments than in the control. Lead content in and Pb extraction by roots and shoots, and bioconcentration factor and translocation factor of C. bursa-pastoris all increased with increasing Pb concentrations in soil. The Pb content in shoots and roots of C. bursa-pastoris exceeded 1000 mg·kg^-1 at 1000 mg·kg^-1 of soil Pb, reaching 1 036.1 mg·kg^-1 and 1 201.4 mg·kg^-1, respectively. The shoot bioconcentration factor of C. bursa-pastoris was greater than 1 when soil Pb concentration was higher than 600 mg·kg^-1, but the translocation factor of C. bursa-pastoris was less than 1 under all Pb treatments. Activities of superoxide dismutase and catalase increased with increases in soil Cd concentration, but malondialdehyde and active oxygen radical content kept in a stable status. Therefore, C. bursa-pastoris is a Pb-accumulator with great accumulation ability, stable translocation and strong tolerance to Pb. which could be used to remediate Pb-contaminated farmland soil.