镉对超富集植物滇苦菜抗氧化系统的影响

Antioxidative defense to cadmium in hyperaccumulator Picris divaricata V.

采用水培实验,研究镉(Cd)对一种新发现的Cd超富集植物——滇苦菜抗氧化系统的影响。结果表明,中、低浓度Cd(1-10μmol.L-1)处理下滇苦菜生物量与对照无显著差异,而高浓度Cd(50-100μmol.L-1)抑制了滇苦菜的生长,整株生物量比对照降低了72%和86%。10μmol.L-1Cd处理下地上部Cd浓度达到270mg·kg-1(干重),转运系数为1.41,符合超富集植物的特征。滇苦菜地上部Cd富集浓度最高达3919mg·kg-1,且64%-87%的Cd分布在地上部。中、低浓度Cd(1-10μmol.L-1)胁迫下,滇苦菜的丙二醛(MDA)和H2O2含量、超氧阴离子自由基(O2.-)产生速率及各抗氧化酶活性与对照没有显著差异。但高浓度Cd(50-100μmol.L-1)胁迫下,地上部MDA、H2O2含量和O2.-产生速率比对照分别提高了5-17、1.6-6倍和2.9-7.2倍,地下部分别提高了1-5、1.4倍和9.5-11倍。同时,高浓度Cd处理下地上部和地下部超氧化物歧化酶(SOD)和过氧化物酶(POD)活性以及地上部谷胱甘肽(GSH)含量显著上升,但谷胱甘肽还原酶(GR)和过氧化氢酶(CAT)活性变化不明显。研究表明,滇苦菜对Cd有较强的富集和转运能力。中、低浓度Cd处理未对滇苦菜造成明显的氧化胁迫,高浓度Cd处理时滇苦菜地上部与地下部均受到氧化胁迫,但对抗氧化胁迫的响应方式不同。

A hydroponic experiment was conducted to investigate the role of the antioxidative defense system in cadmium（Cd）tolerance of a new Cd-hyperaccumulator Picris divaricata V.The results showed that low and moderate levels of Cd（1-10 μmol·L-1）in solution did not affect the growth of P.divaricata,whereas high levels of Cd addition（50-100 μmol·L-1）inhibited the growth,with 72% and 86% biomass reduction compared to the control.Cd concentration in shoots reached 270 mg·kg-1 at 10 μmol·L-1 Cd with a translocation factor of 1.41,in accordance with the characteristics of Cd hyperaccumulation.The maximum shoot concentration of Cd reached 3919 mg·kg-1 and about 64%-87% of total Cd was allocated in the shoots.Addition of 1-10 μmol·L-1 Cd did not affect the amounts of malondialdehyde（MDA）,H2O2,superoxide（O·-2）and the activities of antioxidative enzymes.However,50-100 μmol·L-1 Cd induced the accumulation of MDA,H2O2 and O·-2 both in the shoots and roots,which were increased by 5-17 and 1-5 folds,1.6-6 and 1.4 folds,2.9-7.2 and 9.5-11 folds than those of the control,respectively.Meanwhile,high levels of Cd significantly enhanced the activities of superoxide dismutase（SOD）and peroxidase（POD）in shoots and roots as well as the shoot glutathione（GSH）concentration,but had no obvious effects on the activities of glutathione reducatse（GR）and catalase（CAT）.We concluded here that P.divaricata has a strong capability in Cd accumulation and translocation.Low and moderate addition of Cd did not induce any obvious oxidative stress;high Cd treatments induced the lipid peroxidation and accumulation of reactive oxygen species（ROS）,which might be removed by different mechanisms in shoots and roots.