Lead Induced Changes in the Growth and Antioxidant Metabolism of the Lead Accumulating and Non‐accumulating Ecotypes of Sedum alfredii

Abstract

The phytotoxicity and antioxidative adaptations of lead (Pb) accumulating ecotype (AE) and non-accumulating ecotype (NAE) of Sedum alfredii Hance were investigated under different Pb treatments involving 0, 0.02 mmol/L Pb, 0.1 mmol/L Pb and 0.1 mmol/L Pb/0.1 mmol/L ethylenediaminetetraacetic acid (EDTA) for 6 days. With the increasing Pb level, the Pb concentration in the shoots of AE plants enhanced accordingly, and EDTA supply helped 51% of Pb translocation to shoots of AE compared with those treated with 0.1 mmol/L Pb alone. Moreover, the presence of EDTA alleviated Pb phytotoxicity through changes in plant biomass, root morphology and chlorophyll contents. Lead toxicity induced hydrogen peroxide (H2O2) accumulation and lipid peroxidation in both ecotypes of S. alfredii. The activities of superoxide dismutase (SOD), guaiacol peroxidase (G-POD), ascorbate peroxidase, and dehydroascorbate reductase elevated in both leaves and roots of AE as well as in leaves of NAE with the increasing Pb levels, but SOD and G-POD declined in roots of NAE. Enhancement in glutathione reductase activity was only detected in roots of NAE while a depression in catalase activity was recorded in the leaves of NAE. A significant enhancement in glutathione and ascorbic acid (AsA)levels occurred in both ecotypes exposed to Pb and Pb/EDTA treatment compared with the control, however, the differences between these two treatments were insignificant. The dehydroascorbate (DHA) contents in roots of both ecotypes were 1.41 to 11.22-fold higher than those in leaves, whereas the ratios of AsA to DHA (1.38 to 6.84) in leaves altering more to the reduced AsA form were much higher than those in roots. These results suggested that antioxidative enzymes and antioxidants play an important role in counteracting Pb stress in S. alfredii.

Lead-induced genotoxicity to Vicia faba L. roots in relation with metal cell uptake and initial speciation

“…2B). These results are in line with those of Liu et al (2008) in Sedum alfredii or Ruley et al (2006) who studied Sesbania drummondii, a lead hyper-accumulator. Herná ndez -Allica et al (2007) also reported that proper management of the EDTA concentration can increase the uptake of metals with low phytoavailability like Pb and reduce their phytotoxicity.…”

Lead Uptake, Toxicity, and Detoxification in Plants

“…Several hyperaccumulator plant species, such as Brassica pekinensis and Pelargonium, are capable of translocating higher concentrations of lead to aerial plant parts, without incurring damage to their basic metabolic functions (Xiong et al 2006;Liu et al 2008;Arshad et al 2008). A specific hyperaccumulator species can accumulate more than 1000 ppm lead (Maestri et al 2010).…”

“…Photosynthesis inhibition is a well-known symptom of lead toxicity (Xiong et al 2006;H ue ta l .2007;Liu et al 2008;Piotrowska et al 2009;Sing et al 2010;Cenkci et al 2010). This inhibition is believed to result from the following indirect effects of lead rather than from a direct effect:…”

Different strategies to achieve Pb-tolerance by the two Trebouxia algae coexisting in the lichen Ramalina farinacea

“…Exposure to HMs in general, and to Pb in particular, increases the production of reactive oxygen species (ROS), including superoxide radicals, hydroxyl radicals, and hydrogen peroxide, thereby unbalancing the cellular redox status (Verma and Dubey, 2003;Liu et al, 2008;Słomka et al, 2008;Phang et al, 2011). At high levels, or following acute increases of metal pollutants, algal cells are injured because the resulting ROS levels exceed the capacities of cellular antioxidant protection systems.…”