Comparison of Platinum, Rhodium, and Palladium Bioaccumulation by Sinapis alba and their Influence on Phytochelatin Synthesis in Plant Tissues

Abstract

Phytochelatins are known to play an essential role in xenobiotic detoxification in some plants. Until now, their synthesis in plants exposed to platinum group elements (PGEs), especially Pd and Rh, has not been directly proven. The influence of PGEs on the natural environment, especially on living organisms, is particularly important in view of increasing emissions of these elements from automotive catalytic converters. This paper describes studies related to the identification of the presence of phytochelatins in tissues of white mustard (Sinapis alba L.) exposed to Pt, Rh, and Pd salts. Phytochelatins were identified by high-performance liquid chromatography with two types of detection: fluorescence (FLD) for thiols after derivatization, and electrospray ionization mass spectrometry (ESI MS) for thiols in fresh extracts. Our study confirmed the synthesis of phytochelatins in some plant organs under the influence of PGEs, and illustrated the differences in plant response to stress caused by Pt, Rh, or Pd.

Cycling of Pt, Pd, and Rh Derived from Catalytic Converters: Potential Pathways and Biogeochemical Processes

“…In addition, the Gibbs free energy of formation (∆G) values for PtS, PdS, and Rh 2 S 3 , at standard state conditions, as they are given from the experimental data [34,35] and calculations [36], are −66 kj/moll for PdS, −76 kj/mol for PtS, and −252 kj/mol for Rh 2 S 3 . The more negative Gibbs free energy values for the Rh 2 S 3 compared to those for the PdS and PtS seem to be in good agreement with the lower availability and the lower Rh content in plants (Table 2) and in shoots than in the roots [21]. Thermodynamic properties have also been applied to explain the difference in mobility between Au and Pt [37].…”

“…For example, 8 µg/kg Pt, 25 µg/kg Pd, and 5.5 µg/kg Rh in shoots, and 762 µg/kg Pt, 663 µg/kg Pd, and 437 µg/kg Rh in tree leaves have been noted [21]. In addition, cultivated plants, using Rh salt, have shown as high as 650-1300 accumulation factors for roots and much lower (7) for stems leaves (4) [21].…”

“…The potential environments in which the emitted precious metals are dispersed [10], the soil pH, redox, salinity, and the presence of inorganic (mostly chlorides) and organic ligands (humic acids) may be major controlling factors for the dissolution of Pt, Pd, and Rh, and the oxidation and formation of Pt(II), Pd(II), and Rh(III) complexes [10,12,20,21,25,28].…”

“…The long-distance transport of Pt, Pd, and Rh has been documented for roads, rivers, and lakes [18]. The PGE are emitted in inert form as nanoparticles attached to fine fragments of the original substrate, but their contact with various soil compounds may result from their incorporation into bioavailable molecules and transformation into more mobile species through complexation with organic matter in low pH rainwater [19][20][21]. Microorganisms (primarily bacteria and fungi), which are abundant in natural environments, facilitate biogeochemical processes, such as breaking down organic and inorganic materials and biomineralization (carbonates, oxides, sulfides, silicates, phosphates, phosphates, and silicates) in order to gain energy [22].…”

Toxic Responses of Palladium Accumulation in Duckweed (Lemna minor): Determination of Biomarkers

“…Under these conditions, the accumulated Pd triggered the synthesis of total thiol-containing proteins for metal stress tolerance. Previous studies showed that several metals had activated the synthesis of enzymes such as the phytochelatin synthetase to produce phytochelatins (PCs), permitting control of the intracellular concentration of metals (Supalkova et al 2007;Yao et al 2012;Kińska and Kowalska 2019).ńKińska and Kowalska (2019) detected the synthesis of PC 2 , PC 3 , and PC 4 in leaf tissues of the white mustard Sinapis alba L. cultivated in nutrient solution containing 1 mg/L of PdCl 2 . In the present study, the synthesis of phytochelatins was activated in Pd-treated L. minor plants, but more analysis is needed to quantify the induction of phytochelatins.…”