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

Abstract

Physiological and anatomical features of Cd-tolerance in Pfaffia glomerata were examined by exposing plantlets to nutrient solutions with increasing Cd concentrations (0, 15, 45, and 90 µmol Cd L -1 ), and possible Cd-tolerance markers were established. Cd contents were found to be higher in roots than in shoots. According to the bioconcentration factor data, this species is effectively a Cd-hyperaccumulator, as previously attested. Cd induced the appearance of xeromorphic characteristics in leaves (decreased water potential, increased numbers and decreased stomata size) and increased root endodermis thickness. The enzymatic antioxidant systems of roots and leaves were differently affected by Cd. The coordinated activities of antioxidant enzymes were effective in reducing Cd-induced reactive oxygen species in plants, mainly in leaves. Root endodermis thickness, stomatal size and numbers, root superoxide dismutase, and guaiacol peroxidase, as well as leaf guaiacol peroxidase and catalase activities can all be considered Cd-tolerance markers in Pfaffia glomerata. Due to its high root Cd accumulation, Pfaffia glomerata may be useful in Cd-phytoextraction programs, however the pharmacological use of plants grown in the presence of Cd must be avoided.

Physiological exegesis of growth parameters in Amranthus tricolor inoculated with Cd resistant bacteria

“…The findings suggested that the rhizosphere bacteria were crucial to the plants' ability to absorb metal in their shoots. Similar findings were made by Gomes et al, (2012) who reported that increasing Cd supply increased Pfaffia glomerata's Cd absorption. Plants use their root tissue as a defensive mechanism to shield their above-ground components from too much Cd and to prevent Cd from moving to their shoots.…”

Trace Elements Tolerance Modulated by Antioxidant System in Plants

“…Studies of these responses in the leaves of tolerant Brazilian species have, however, revealed that SOD did not show any type of As-, Zn-, or Cd-inducing inhibition in the As-tolerant Anadenanthera peregrina (Gomes et al, 2013b), the Zn-tolerant Myracrodruon urundeuva (Gomes et al, 2013c), or the Cd-tolerant (and hyperaccumulator) Pfaffia glomerata (Gomes et al, 2013e) respectively; and SOD activity was always higher in treated seedlings. Increases in SOD activity have been linked to higher values of superoxide radical concentrations due to the synthesis of enzymes induced by superoxide-mediated signal transduction (Rossato et al, 2011).…”

“…Interestingly, the addition of phosphorus to the growth substrate increased As-tolerance in A. peregrina by increasing APX activity, which decreased H 2 O 2 accumulation and helped prevent lipid peroxidation in its leaves (Gomes et al, 2013b). Similarly, P. glomerata seedlings exposed to Cd doses up to 90 mmol L 21 showed increased APX activity , or were not affected (Gomes et al, 2013e), and no growth reductions were observed under those conditions.…”