Effect of cadmium on growth, micronutrient concentration, and δ-aminolevulinic acid dehydratase and acid phosphatase activities in plants of Pfaffia glomerata

Abstract

Pfaffia glomerata (Spreng.) Pedersen plantlets were grown under different cadmium (Cd) concentrations (0, 20, 40, 60 and 80 μM) in a hydroponic system during 7 d. Plant growth, micronutrient, chlorophyll and carotenoid concentrations, as well as δ-aminolevulinic acid dehydratase (ALA-D; E.C.4.2.1.24) and acid phosphatase (AP; E.C.3.1.3.2) activities were analysed. Cadmium concentration in both shoots and roots increased with increasing external Cd levels. Metal concentration in roots were on average 12-fold higher than in shoot tissues. Root length was unaffected by Cd treatments. In contrast, dry weight of both shoot and roots increased significantly after exposure to 20 and 40 μM Cd. Additionally, shoot and total plant dry weight were only reduced in plants exposed to 80 μM Cd. In contrast, root dry weight decreased significantly after exposure with Cd concentrations above 40 μM. A micronutrient-and organdependent response to Cd toxicity was observed. Zinc and Cu concentrations in both, shoot and roots did not alter due to exposure to Cd. Cadmium stress reduced Mn uptake but not its translocation within the plant. A synergistic effect of Cd on Fe concentration in root at 20 μM and 80 μM Cd levels was observed. The activity of AP, and especially that of ALA-D, was reduced with increasing Cd levels. At these Cd levels, the chlorophyll concentration was also reduced. There was a positive correlation between concentrations of carotenoids and chlorophylls. Our results indicate that P. glomerata seems to have some degree of Cd tolerance. parte aérea. O comprimento das raízes não foi afetado pelos tratamentos de Cd. Em contraste, a biomassa seca da parte aérea e raízes aumentou significativamente pela adição de 20 e 40 μM Cd. Além disso, a biomassa seca total das plantas somente diminuiu no nível de 80 μM Cd em relação à das plantas-controle. Por outro lado, a biomassa radicular diminuiu significativamente pela adição de Cd a níveis superiores a 40 μM. Constatou-se resposta dependente do órgão e do micronutriente à toxicidade de Cd. As concentrações de Zn e Cu na parte aérea e raízes não foram alteradas pela presença de Cd. A absorção de Mn foi diminuída pelo estresse de Cd, porém sua translocação não foi alterada. Um efeito sinergístico do Cd na concentração de Fe nas raízes foi observado nos níveis de 20 e 80 μM Cd. As atividades da ALA-D e AP foram diminuídas com o incremento dos níveis de Cd, porém a ALA-D foi mais afetada. Naquelas concentrações de Cd, a concentração de clorofila também foi diminuída. Houve uma correlação positiva entre as concentrações de carotenóides e clorofila. Os resultados indicam que a P. glomerata parece ter algum grau de tolerância ao Cd.palavras-chave: carotenóides, clorofilas, fitorremediação, ginseng brasileiro, micronutrientes, metal pesado.

Ecophysiological adaptation and metal accumulation in water hyacinth from two tropical rivers

“…Preferential accumulation of metals in plant roots, as observed in the present study, seems to be a generalized strategy to minimize damages caused by these elements in plants (Vitória et al, 2001;Pereira et al, 2002;Skrebsky et al 2008). Other studies on water hyacinth have also shown this (Soltan and Rashed 2003;Lu et al, 2004;Mangabeira et al, 2004;Olivares-Reiumont et al, 2007;Paiva et al, 2009).…”

Aluminum accumulation in two Pfaffia glomerata genotypes and its growth effects

“…Some hyperaccumulator plants, which may serve as a good tool for phytoremediation, are characterized by a shootto-root metal concentration ratio (i-e. the translocation factor) of more than 1, whereas non-hyperaccumulator plants usually have higher metal concentrations in the roots than in the shoots (AL-QAHTANI, 2012). Based on previous studies (SKREBSKY at al., 2008;CALGAROTO et al, 2011;GUPTA et al, 2011), P. glomerata plants may accumulate considerable amounts of metals such as mercury, lead and cadmium in the roots without extensive damage to the plants. In this study, BRA accession had significantly higher (two fold) root Al concentration than JB/UFSM accession (Figure 1b).…”

“…Taking into account that P. glomerata has shown some degree of heavy metal tolerance, such as for Cd (SKREBSKY et al, 2008), Hg (CALGAROTO et al, 2011), and for Pb (GUPTA et al, 2011), as well as for Al as shown in the present study, and considering that the ingestion of Al has a great potential risk to human health, the screening for genotypes of P. glomerata that accumulate less Al and other metals mainly in the root tissues must be prioritized for purposes of cropping.…”

Cd-tolerance markers of Pfaffia glomerata (Spreng.) Pedersen plants: anatomical and physiological features

“…Water balance disturbances have been reported in plants under heavy metal stress (Barceló et al, 1990;Wójcik et al, 2005), probably due to changes in size and number of xylem vessels resulting from alterations in plant hormonal balances (Poschenrieder and Barceló, 1999). Heavy metal effects on chlorophyll biosynthesis related to changes in δ-ALA-D enzyme activity have been reported (Skrebsky et al, 2008), and decreased water potentials and resulting tissue dehydration were also related to decreased δ-ALA-D activity (Singh et al, 1997), which catalyzes the condensation of two molecules of δ-aminolevulinic acid -ALA to porphobilinogen (Gibson et al, 1955). Nevertheless, at least to the studied time, reductions in plant water status and chlorophyll levels apparently did not provoke exaggerated effects on the photosynthetic system of Pfaffia glomerata as those plants did not show any detectable reductions in shoot biomass production.…”

“…Although native vegetation types growing on naturally mineralized or metal-contaminated sites have been described in Brazil, relatively few potential phytoremediator species were also identified (Ginocchio and Baker, 2004). Carneiro et al (2002) reported high growth rates and apparent tolerance of the species of genus Pfaffia to soils contaminated with Cd and Zn (90 and 1,450 mg kg -1 respectively), and Skrebsky et al (2008), Calgaroto et al (2010), and Gupta et al (2011) demonstrated reasonable degrees of Cd, Hg, and Pb tolerances in Pfaffia glomerata (Spreng.) Pedersen.…”