铅胁迫对金丝草AsA-GSH循环及铅积累的影响

Influence of lead stress on the ascorbate-glutathione cycle and subcellular distribution in leaves and roots of Pogonatherum crinitum

为了探究金丝草的耐铅(Pb)机制,以金丝草为材料,测定不同浓度(0、1000、2000、3000 mg·kg-1)Pb胁迫下金丝草抗坏血酸-谷胱甘肽(As A-GSH)循环和亚细胞分布等指标。结果表明:低浓度(1000 mg·kg-1)Pb胁迫下金丝草叶片谷胱甘肽还原酶(GR)、还原型谷胱甘肽(GSH)、抗坏血酸(As A)含量高于对照,但未达显著水平(P>0.05);金丝草根系GR、As A、抗坏血酸过氧化物酶(APX)含量则显著增加(P<0.05),较对照增长41.1%、60.6%和74.0%。同时,低浓度(1000 mg·kg-1)Pb胁迫对金丝草根系总根长、根表面积、根平均直径和根体积也有一定促进作用。高浓度(2000、3000 mg·kg-1)Pb胁迫下,金丝草根系总根长、根表面积和根体积显著降低(P<0.05),叶片及根系细胞内叶绿体、线粒体、核仁等亚细胞器损伤严重,毒害作用渐显。但金丝草叶片和根系GR、GSH、As A含量在高浓度Pb处理下仍高于对照,细胞壁和可溶性组分Pb含量显著高于低浓度Pb处理(P<0.05),且两组分Pb含量占总量69%以上。研究表明,金丝草可通过诱导体内As A-GSH循环响应和Pb在亚细胞的差异化分配,增强植株抗氧化能力,限制Pb转运及其对细胞活跃区域的毒害来适应土壤Pb逆境。

Pogonatherum crinitum, an effective plant for phytoremediation, can grow in soils polluted with heavy metals and subsequently accumulate large amounts of heavy metals. In order to understand its response to heavy metal stress, a pot culture experiment was carried out at different lead concentrations. The results showed that the contents of glutathione reductase （GR）, glutathione（ GSH ）, ascorbic acid（ AsA ） in the leaves of P. crinitum were higher than those of the control samples under low Pb concentrations （ 1000 mg· kg^-1 ）, but not significantly. The contents of GR, AsA, and ascorbate peroxidase（ APX ） in the roots significantly increased by 41.1%, 60.6%, and 74.0%, respective- ly, compared with those of the control samples. Low Pb concentrations had certain promotional effects on the total root length, root surface area, root mean diameter, and root volume. However, increasing Pb concentrations caused inhibitory effects on the plant, with the total root length, root surface area, and root volume decreasing significantly. In addition, increased subcellular damage occurred in the leaves and roots under high Pb concentrations（2000, 3000 mg· kg^-1）. The contents of GR, GSH, and AsA in the leaves and roots of P. crinitum were higher than those in the control samples under high Pb treatments and the Pb contents in cell wall and soluble constituent subcellular compo- nents accounted for over 69% of the total. These findings indicated that P. crinitum adapted to the Pb stress by inducing the ascorbate-glutathione（AsA-GSH） cycle and by changing the subcellular distribution of Pb, which showed potential application in the remediation of Pbpolluted soil.