Lyubenova Lyudmila, Nehnevajova Erika, Herzig Rolf, Schröder Peter
Department Microbe Plant Interactions, Helmholtz Zentrum München, German Research Center for Environmental Health, 85764 Neuerberg, Germany.
Environ Sci Pollut Res Int. 2009 Jul;16(5):573-81. doi: 10.1007/s11356-009-0175-8. Epub 2009 May 14.
BACKGROUND, AIM, AND SCOPE: Tobacco, Nicotiana tabacum, is a widely used model plant for growth on heavy-metal-contaminated sites. Its high biomass and deep rooting system make it interesting for phytoextraction. In the present study, we investigated the antioxidative activities and glutathione-dependent enzymes of different tobacco clones optimized for better Cd and Zn accumulation in order to characterize their performance in the field.
The improved heavy metal resistance also makes the investigated tobacco clones interesting for understanding the plant defense enzyme system in general. Freshly harvested plant material (N. tabacum leaves) was used to investigate the antioxidative cascade in plants grown on heavy metal contaminated sites with and without amendments of different ammonium nitrate and ammonium sulfate fertilizers.
Plants were grown on heavily polluted soils in north-east Switzerland. Leaves were harvested at the field site and directly deep frozen in liquid N(2). Studies were concentrated on the antioxidative enzymes of the Halliwell-Asada cycle, and spectrophotometric measurements of catalase (CAT, EC 1.11.1.6), ascorbate peroxidase (APX, EC 1.11.1.11), superoxide dismutase (SOD, EC 1.15.1.1), glutathione peroxidase (GPX, EC 1.11.1.9), glutathione reductase (GR, EC 1.6.4.2), glutathione S-transferase (GST, EC 2.5.1.18) were performed.
We tried to explain the relationship between fertilizer amendments and the activity of the enzymatic defense systems. When tobacco (N. tabacum) plants originating from different mutants were grown under field conditions with varying fertilizer application, the uptake of cadmium and zinc from soil increased with increasing biomass. Depending on Cd and Zn uptake, several antioxidant enzymes showed significantly different activities. Whereas SOD and CAT were usually elevated, several other enzymes, and isoforms of GST were strongly inhibited.
Heavy metal uptake represents severe stress to plants, and specific antioxidative enzymes are induced at the cost of more general reactions of the Halliwell-Asada cycle. In well-supplied plants, the glutathione level remains more or less unchanged. The lack of certain glutathione S-transferases upon exposure to heavy metals might be problematic in cases when organic pollutants coincide with heavy metal pollution. When planning phytoremediation of sites, mixed pollution scenarios have to be foreseen and plants should be selected according to both, their stress resistance and hyperaccumulative capacity.
背景、目的及范围：烟草（Nicotiana tabacum）是一种广泛应用于重金属污染场地生长的模式植物。其高生物量和深根系使其在植物提取方面具有吸引力。在本研究中，我们调查了为更好地积累镉和锌而优化的不同烟草克隆的抗氧化活性和谷胱甘肽依赖性酶，以表征它们在田间的表现。
提高的重金属抗性也使所研究的烟草克隆在总体上对于理解植物防御酶系统具有吸引力。使用新鲜收获的植物材料（烟草叶片）来研究在添加和不添加不同硝酸铵和硫酸铵肥料的情况下，生长在重金属污染场地的植物中的抗氧化级联反应。
植物在瑞士东北部的重度污染土壤中生长。在田间采集叶片并直接在液氮中速冻。研究集中于哈氏-阿萨达循环的抗氧化酶，并对过氧化氢酶（CAT，EC 1.11.1.6）、抗坏血酸过氧化物酶（APX，EC 1.11.1.11）、超氧化物歧化酶（SOD，EC 1.15.1.1）、谷胱甘肽过氧化物酶（GPX，EC 1.11.1.9）、谷胱甘肽还原酶（GR，EC 1.6.4.2）、谷胱甘肽S-转移酶（GST，EC 2.5.1.18）进行分光光度测量。
我们试图解释肥料添加与酶促防御系统活性之间的关系。当源自不同突变体的烟草植株在田间条件下生长并施用不同肥料时，土壤中镉和锌的吸收量随生物量增加而增加。根据镉和锌的吸收情况，几种抗氧化酶表现出显著不同的活性。虽然超氧化物歧化酶和过氧化氢酶通常升高，但其他几种酶以及谷胱甘肽S-转移酶的同工型受到强烈抑制。
重金属吸收对植物构成严重胁迫，特定的抗氧化酶被诱导，这是以哈氏-阿萨达循环的更一般反应为代价的。在养分充足的植物中，谷胱甘肽水平或多或少保持不变。在有机污染物与重金属污染同时存在的情况下，暴露于重金属时某些谷胱甘肽S-转移酶的缺乏可能会成为问题。在规划场地的植物修复时，必须预见混合污染情况，并且应根据植物的抗逆性和超积累能力来选择植物。
