Search

The large-scale use of quaternary ammonium compounds (QACs) in medicines or disinfectants can lead to their release into the environment, posing a potential risk to organisms. This study examined the effects of three typical QACs, dodecyltrimethylammonium chloride (DTAC), dodecyldimethylbenzylammonium chloride (DBAC), and didodecyldimethylammonium chloride (DDAC), on hydroponically cultured wheat seedlings. After 14 days of exposure, both hormesis and phytotoxicity were observed in the wheat seedlings. The shoot and root fresh weight gradually increased as QAC concentrations rose from 0.05 to 0.8 mg L-1. However, higher QAC concentrations severely inhibited plant growth by decreasing shoot and root fresh weight, total root length, and photosynthetic pigment content. Moreover, the increase in malondialdehyde and O-2(.-) contents, as well as root membrane permeability, reflected an oxidative burst and membrane lipid peroxidation caused by QACs. However, the effects of QACs on the levels of these oxidative stress markers were compound-specific, and the changes in superoxide dismutase, peroxidases, and catalase activity were partly related to reactive oxygen species levels. Considering the order of median effective concentration values (EC50) and the levels of oxidative stress induced by the three tested QACs, their phytotoxicities in wheat seedlings increased in the following order: DDAC < DTAC < DBAC, which mainly depended on their characteristics and applied concentrations. These results, which illustrated the complexity of QAC toxicity to plants, could potentially be used to assess the risk posed by these compounds in the environment.

Microorganisms are used to alleviate heavy metal stress in plants cultivated in contaminated fields. However, the relevant mechanisms have been rarely explored. The goal of this study was to investigate effects of arbuscular mycorrhizal fungus Funneliformis mosseae and two Cd-resistant bacterial strains (Enterobacter sp. EG16 and Enterobacter ludwigii DJ3) on growth and Cd tolerance of tomato when applied with different inoculation strategies (single or dual) and Cd concentrations (50 and 100 mg kg−1). Better plant growth was observed in mycorrhizal alone or combined treatments. In F. mosseae and EG16 co-inoculation treatment, shoot and root dry weight were 119–154% and 91–173% higher than those of the control, respectively. Higher bacterial and mycorrhizal colonization rate and root Cd concentration were also found in this treatment. However, the decrease of shoot Cd concentration and translocation factor values indicated this treatment was effective in improving Cd tolerance of the host plants. In addition, the increase in soil pH and decline in bioavailable Cd in the rhizosphere might be partly involved in reduction of Cd accumulation in plants. Our results suggest that co-inoculation with suitable microorganisms is important in plant growth and tolerance to Cd in Cd-contaminated soil.

Novel alternatives of perfluorooctane sulfonate (PFOS), chlorinated polyfluorinated ether sulfonates (Cl-PFAESs) are increasingly being detected in the aquatic and terrestrial environment. Previous studies mainly focused on aquatic biota; however, the knowledge about the ecotoxicological risk they pose to terrestrial plants was still lacking. In this study, the accumulation of two Cl-PFAES (6:2 and 8:2 Cl-PFAES) and PFOS in wheat seedlings at environmentally relevant levels (50 and 100 μg L−1) was investigated. Concentrations of Cl-PFAESs in the roots were an order of magnitude higher than those in shoots, indicating that they were primarily accumulated in the roots. The values of root and shoot bioconcentration factor was comparable between 6:2 Cl-PFAES and PFOS. However, these indexes of 8:2 Cl-PFAES were 42–91% higher and 70–76% lower than PFOS, respectively. As a result, 6:2 Cl-PFAES had a similar accumulation pattern as PFOS, whereas 8:2 Cl-PFAES was predominantly restricted to the roots, which might be attributed to their hydrophobicity and carbon chain length. In addition, at 250 mg L−1 of Cl-PFAESs, plant biomass and pigment content were 24–30% and 0.4–18%, respectively, which were lower than those of PFOS. As compared with PFOS, Cl-PFAESs induced higher levels of root membrane permeability, reactive oxygen species and malondialdehyde content, as well as reduced the activities of antioxidant enzymes and glutathione content. These suggested the occurrence of a severer oxidative damage and the breakdown of the antioxidant defence system in wheat cells. Therefore, we conclude that Cl-PFAESs might pose a higher potential threat to the environment than PFOS.

Phthalate acid esters (PAEs) are of particular concern due to their potential environmental risk to human and nonhuman organisms. Although uptake of PAEs by plants has been reported by several researchers, information about the intracellular distribution and uptake mechanisms of PAEs is still lacking. In this study, a series of hydroponic experiments using intact pumpkin (Cucurbita moschata) seedlings was conducted to investigate how di-n-butyl phthalate (DnBP), one of the most frequently identified PAEs in the environment, enters and is distributed in roots. DnBP was transported into subcellular tissues rapidly in the initial uptake period (

Siderophores, as strong chelators specific to iron, have been intensively studied in relation to the facilitation of biological iron acquisition from iron oxides. In this study, the dissolution of hematite in the presence of the siderophore desferrioxamine B (DFOB) and three low-molecular-weight organic acids (LMWOAs, i.e., oxalic, citric, or malic acid) was investigated at three pH conditions (3.0, 5.5, and 9.0). Hematite dissolution was pH-dependent and LMWOA-specific. The adsorption of DFOB on hematite was significantly higher at pH 9.0 than at the other pH values. The adsorption of oxalic acid on hematite, however, showed a descending trend as pH was increased, and adsorption of citric and malic acids was not significantly affected by pH. The Fourier transform infrared (FTIR) results also indicated the occurrence of these ligands’ adsorption. After acidification, dissolved iron was detected only in suspensions of hematite pre-adsorbed with oxalic acid at pH 5.5 and 9.0 or pre-adsorbed with citric acid at pH 5.5, indicating that these LMWOAs promoted the formation of labile iron on the hematite surface. Based on previous research and the results of this study, a hypothetical model is proposed. These results provide insight into the effect of LMWOAs on the dissolution of hematite promoted by DFOB.