Belgian Nuclear Research Institute, Environmental Health and Safety, Biosphere Impact Studies, Mol, Belgium; Centre for Environmental Sciences, Hasselt University, Diepenbeek, Belgium.
Plant Biol (Stuttg). 2015 Jan;17 Suppl 1:91-100. doi: 10.1111/plb.12222. Epub 2014 Jul 29.
Common duckweed (Lemna minor L.) is ideally suited to test the impact of metals on freshwater vascular plants. Literature on cadmium (Cd) and uranium (U) oxidative responses in L. minor are sparse or, for U, non-existent. It was hypothesised that both metals impose concentration-dependent oxidative stress and growth retardation on L. minor. Using a standardised 7-day growth inhibition test, the adverse impact of these metals on L. minor growth was confirmed, with EC50 values for Cd and U of 24.1 ± 2.8 and 29.5 ± 1.9 μm, respectively, and EC10 values of 1.5 ± 0.2 and 6.5 ± 0.9 μm, respectively. The metal-induced oxidative stress response was compared through assessing the activity of different antioxidative enzymes [catalase, glutathione reductase, superoxide dismutase (SOD), ascorbate peroxidase (APOD), guaiacol peroxidase (GPOD) and syringaldizyne peroxidase (SPOD)]. Significant changes in almost all antioxidative enzymes indicated their importance in counteracting the U- and Cd-imposed oxidative burden. However, some striking differences were also observed. For activity of APODs and SODs, a biphasic but opposite response at low Cd compared to U concentrations was found. In addition, Cd (0.5-20 μm) strongly enhanced plant GPOD activity, whereas U inhibited it. Finally, in contrast to Cd, U up to 10 μm increased the level of chlorophyll a and b and carotenoids. In conclusion, although U and Cd induce similar growth arrest in L. minor, the U-induced oxidative stress responses, studied here for the first time, differ greatly from those of Cd.
普通浮萍（Lemna minor L.）非常适合用来测试金属对淡水维管束植物的影响。关于浮萍（L. minor）对镉（Cd）和铀（U）氧化响应的文献很少，或者说铀（U）不存在。因此，假设这两种金属都会对浮萍（L. minor）造成浓度依赖性的氧化应激和生长迟缓。通过使用标准化的 7 天生长抑制测试，证实了这些金属对浮萍（L. minor）生长的不良影响，Cd 和 U 的 EC50 值分别为 24.1 ± 2.8 和 29.5 ± 1.9 μm，EC10 值分别为 1.5 ± 0.2 和 6.5 ± 0.9 μm。通过评估不同抗氧化酶（过氧化氢酶、谷胱甘肽还原酶、超氧化物歧化酶（SOD）、抗坏血酸过氧化物酶（APOD）、愈创木酚过氧化物酶（GPOD）和丁香醛过氧化物酶（SPOD））的活性，比较了金属诱导的氧化应激反应。几乎所有抗氧化酶的活性都发生了显著变化，表明它们在对抗 U 和 Cd 施加的氧化负荷方面非常重要。然而，也观察到了一些显著的差异。对于 APODs 和 SODs 的活性，在低 Cd 浓度下与 U 浓度相比，发现了双相但相反的反应。此外，Cd（0.5-20 μm）强烈增强了植物 GPOD 的活性，而 U 则抑制了它。最后，与 Cd 不同，U 增加到 10 μm 会增加叶绿素 a 和 b 以及类胡萝卜素的水平。总之，尽管 U 和 Cd 都会导致浮萍（L. minor）生长停滞，但这里首次研究的 U 诱导的氧化应激反应与 Cd 有很大的不同。
