Different strategies of cadmium detoxification in the submerged macrophyte Ceratophyllum demersum L.
Different strategies of cadmium detoxification in the submerged macrophyte Ceratophyllum demersum L.
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DOI：
10.1039/c3mt00088e
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发表时间：
2013-01-01
期刊：
影响因子：
3.4
通讯作者：
Kuepper, Hendrik
中科院分区：
文献类型：
--
作者：
Andresen, Elisa;Mattusch, Juergen;Kuepper, Hendrik
重金属镉(Cd)对植物有很强的毒性。为了了解无根沉水植物对Cd的耐性和抗性机制，我们在与环境相关的条件下，用亚微摩尔浓度的Cd处理无根沉水植物金鱼藻。X射线荧光测量表明，在无毒(0.2 nM，2 nM)、中毒(20 NM)和剧毒(200 NM)Cd水平下，Cd和Zn的分布模式发生了变化。随着Cd浓度的增加，Cd向非光合作用组织如表皮和叶脉的吸收增加。在镉中毒浓度下，锌重新分布，并主要存在于静脉中。Cd处理诱导了植物体内植物络合素(PC)的合成，PC3的诱导阈值已经在20 nM Cd。相比之下，在铜处理的植物中，只有在最高浓度(100-200 NM铜)时才能检测到PC水平的升高。我们的结果表明，像金龟子这样的非蓄积者也会在重金属对代谢途径干扰最小的组织中储存有毒金属，但残留的毒性会干扰微量营养素的分配。此外，我们还发现，植物螯合素的诱导与金属浓度不成正比，但有一个明显的阈值，对每种PC都是特定的。最后，我们可以证明，以前被认为对大多数植物无毒的20 nM Cd已经诱导了解毒机制。
The heavy metal cadmium (Cd) is highly toxic to plants. To understand the mechanisms of tolerance and resistance to Cd, we treated the rootless, submerged macrophyte Ceratophyllum demersum L. with sub-micromolar concentrations of Cd under environmentally relevant conditions. X-ray fluorescence measurements revealed changing distribution patterns of Cd and Zn at non-toxic (0.2 nM, 2 nM), moderately toxic (20 nM) and highly toxic (200 nM) levels of Cd. Increasing Cd concentrations led to enhanced sequestration of Cd into non-photosynthetic tissues like epidermis and vein. At toxic Cd concentrations, Zn was redistributed and mainly found in the vein. Cd treatment induced the synthesis of phytochelatins (PCs) in the plants, with a threshold of induction already at 20 nM Cd for PC3. In comparison, in plants treated with Cu, elevated PC levels were detected only at the highest concentrations (100-200 nM Cu). Our results show that also non-accumulators like C. demersum store toxic metals in tissues where the heavy metal interferes least with metabolic pathways, but remaining toxicity interferes with micronutrient distribution. Furthermore, we found that the induction of phytochelatins is not proportional to metal concentration, but has a distinct threshold, specific for each PC species. Finally we could show that 20 nM Cd, which was previously regarded as non-toxic to most plants, already induces detoxifying mechanisms.