To investigate the effect of arbuscular mycorrhizal fungi (AMF) on boron (B) toxicity in plants under the combined stresses of salt and drought, Puccinellia tenuiflora was grown in the soil with the inoculation of Funneliformis mosseae and Claroideoglomus etunicatum. After three weeks of treatment, the plants were harvested to determine mycorrhizal colonization rates, plant biomass, as well as tissue B, phosphorus, sodium, and potassium concentrations. The results show that the combined stresses reduced mycorrhizal colonization. Mycorrhizal inoculation significantly increased plant biomass while reduced shoot B concentrations. Mycorrhizal inoculation also slightly increased shoot phosphorus and potassium concentrations, and reduced shoot sodium concentrations. F. mosseae and C. etunicatum were able to alleviate the combined stresses of B, salt, and drought. The two fungal species and their combination showed no significant difference in the alleviation of B toxicity. It is inferred that AMF is able to alleviate B toxicity in P. tenuiflora by increasing biomass and reducing tissue B concentrations. The increase in plant phosphorus and potassium, as well as the decrease in sodium accumulation that induced by AMF, can help plant tolerate the combined stresses of salt and drought. Our findings suggest that F. mosseae and C. etunicatum are potential candidates for facilitating the phytoremediation of B-contaminated soils with salt and drought stress.

Rhizospheric microbes play important roles in plant growth and heavy metals (HMs) transformation, possessing great potential for the successful phytoremediation of environmental pollutants. In the present study, the rhizosphere of Elsholtzia haichowensis Sun was comprehensively studied to uncover the influence of environmental factors (EFs) on the whole microbial communities including bacteria, fungi and archaea, via quantitative polymerase chain reaction (qPCR) and high-throughput sequencing. By analyzing molecular ecological network and multivariate regression trees (MRT), we evaluated the distinct impacts of 37 EFs on soil microbial community. Of them, soil pH, HMs, soil texture and nitrogen were identified as the most influencing factors, and their roles varied across different domains. Soil pH was the main environmental variable on archaeal and bacterial community but not fungi, explaining 25.7%, 46.5% and 40.7% variation of bacterial taxonomic composition, archaeal taxonomic composition and a-diversity, respectively. HMs showed important roles in driving the whole microbial community and explained the major variation in different domains. Nitrogen (NH4-N, NO3-N, NO2-N and TN) explained 47.3% variation of microbial population composition and 15.9% of archaeal taxonomic composition, demonstrating its influence in structuring the rhizospheric microbiome, particularly archaeal and bacterial community. Soil texture accounted for 10.2% variation of population composition, 28.9% of fungal taxonomic composition, 19.2% of fungal a-diversity and 7.8% of archaeal a-diversity. Rhizosphere only showed strong impacts on fungi and bacteria, accounting for 14.7% and 4.9% variation of fungal taxonomic composition and bacterial a-diversity. Spatial distance had stronger influence on bacteria and archaea than fungi, but not as significant as other EFs. For the first time, our study provides a complete insight into key influential EFs on rhizospheric microbes and how their roles vary across microbial domains, giving a hand for understanding the construction of microbial communities in rhizosphere.

Trace elements (TEs) availability, biochemical activity and functional gene diversity was studied in a Cu-contaminated soil, revegetated for six years with a mixed stand of willow, black poplar, and false indigo-bush, and amended or not with compost plus dolomitic limestone (OMDL). The OMDL amendment significantly reduced Cu and As availability and soil toxicity, and increased the biochemical activity and microbial functional diversity assessed with the GEOCHIP technique, as compared to the unamended soil (Unt). The OMDL soil showed significantly higher abundance of 25 functional genes involved in decomposition organic compounds, and 11, 3 and 11 functional genes involved in the N, P and S biogeochemical cycles. Functional gene abundance was positively correlated with nutrient contents but negatively correlated with Cu availability and soil toxicity. The abundance of microbial functional genes encoding for resistance to various TEs also increased, possibly due to the microbial proliferation and lower Cu exposure in the presence of high total soil Cu concentration. Genes encoding for antibiotic resistance due to the co-occurrence of TEs and antibiotic resistant genes on genetic mobile elements. Overall, phytomanagement confirmed its potential to restore the biological fertility and diversity of a severely Cu-contaminated soil, but the increase of TEs and antibiotic resistant gene abundances deserve attention in future studies.

We investigated the ability of the aquatic fern Azolla to take up ciprofloxacin (Cipro), as well as the effects of that antibiotic on the N-fixing process in plants grown in medium deprived (-N) or provided (+N) with nitrogen (N). Azolla was seen to accumulate Cipro at concentrations greater than 160 μg g⁻¹ dry weight when cultivated in 3.05 mg Cipro l⁻¹, indicating it as a candidate for Cipro recovery from water. Although Cipro was not seen to interfere with the heterocyst/vegetative cell ratios, the antibiotic promoted changes with carbon and nitrogen metabolism in plants. Decreased photosynthesis and nitrogenase activity, and altered plant's amino acid profile, with decreases in cell N concentrations, were observed. The removal of N from the growth medium accentuated the deleterious effects of Cipro, resulting in lower photosynthesis, N-fixation, and assimilation rates, and increased hydrogen peroxide accumulation. Our results shown that Cipro may constrain the use of Azolla as a biofertilizer species due to its interference with nitrogen fixation processes.

It is desirable to establish an environmentally benign platform for disposing biomass from the phytoremediation process while recovering energy is of importance. To this end, the biochemical methane potential (BMP) tests were conducted using four different biomass samples (i.e., sunflower: Helianthus annuus) that were obtained from the different remediation sites. In particular, this study laid great emphasis on evaluating the inhibition for the anaerobic digestion (AD) process induced by endogenous heavy metal (Cd, Cu, Ni, Pb, and Zn) content in biomass. Despite the high levels of heavy metal contents (Cd: 58.4, Cu: 23.0, Ni: 2.01, Pb: 9.88, and Zn: 146 mg kg⁻¹) in the substrate for the AD process, the overall performance was comparable relative to the case of the references. Therefore, this study signified that the inhibition derived from heavy metals was nearly negligible, which suggested that biomass from the phytoremediation site could be used as a substrate for the AD process.

Poor air quality is an emerging world-wide problem, with most urban air pollutants arising from vehicular emissions. As such, localized high pollution environments, such as traffic tunnels pose a significant health risk. Phytoremediation, including the use of active (ventilated) green walls or botanical biofilters, is gaining recognition as a potentially effective method for air pollution control. Research to date has tested the capacity of these systems to remove low levels of pollutants from indoor environments. If botanical biofilters are to be used in highly polluted environments, the plants used in these systems must be resilient, however, this idea has received minimal research. Thus, testing was conducted to assess the hardiness of the vegetated component of a botanical biofilter to simulated street level air pollutant exposure. A range of morphological, physiological, and biochemical tests were conducted on 8 common green wall plant species prior to and post 5-week exposure to highly concentrated diesel fuel combustion effluent; as a pilot study to investigate viability in in situ conditions. The results indicated that species within the fig family were the most tolerant species of those assessed. It is likely that species within the fig family can withstand enhanced air pollutant conditions, potentially a result of its leaf morphology and physiology. Other species tested were all moderately tolerant to the pollution treatment. We conclude that most common green wall plant species have the capacity to withstand high pollutant environments, however, extended experimentation is needed to rule out potential long term effects along with potential decreases in filter efficiency from accumulative effects on the substrate.

While phosphate (P) inhibits arsenic (As) uptake by plants, phytate increases As uptake by As-hyperaccumulator Pteris vittata. Here we tried to understand the underling mechanisms by investigating the roles of phytate in soil As desorption, P transport in P. vittata, short-term As uptake, and plant growth and As accumulation from soils. Sterile soil was used to exclude microbial degradation on phytate. Results showed that inorganic P released 3.3-fold more As than that of phytate from soil. However, P. vittata accumulated 2–2.5 fold more As from soils with phytate than that in control and P treatment. In addition, different from P suppression on As uptake, solution uptake experiment showed that As uptake in phytate treatment was comparable to that of control under 0.1–7.5 μM As after 1–24 h. Moreover, responding to phytate, P. vittata P transporter PvPht1;3 increased by 3-fold while PvPht1;1 decreased by 65%. The data suggested that phytate upregulated PvPht1;3, thereby contributing to As uptake in P. vittata. Our results showed that, though with lower As release from soil compared to P, phytate induced more As uptake and better growth in P. vittata by upregulating P transporters.

The phenylurea herbicide, linuron (LIN), is used to control various types of weeds. Despite its efficient role in controlling weeds, it presents a persistent problem to the environment. In the current study, phytoremediation properties of transgenic CYP1A2 Arabidopsis thaliana plants to LIN were assessed. CYP1A2 gene was firstly cloned and expressed in bacteria before proceeding to plants. In presence of LIN, The growth of CYP1A2 expressing bacteria was superior compared to control bacteria transformed with the empty bacterial expression vector pET22b(+). No clear morphological changes were detected on CYP1A2 transgenic plants. However, significant resistance to LIN herbicide application either via spraying the foliar parts of the plant or via supplementation of the herbicide in the growth medium was observed for CYP1A2 transformants. Plant growth assays under LIN stress provide strong evidence for the enhanced capacity of transgenic lines to grow and to tolerate high concentrations of LIN compared to control plants. HPLC analyses showed that detoxification of LIN by bacterial extracts and/or transgenic plant leaves is improved as compared to the corresponding controls. Our data indicate that over expression of the human CYP1A2 gene increases the phytoremediation capacity and tolerance of Arabidopsis thaliana plants to the phenylurea herbicide linuron.

Constructed wetlands (CWs) are a promising technology to treat pesticide contaminated water, but its implementation is impeded by lack of data to optimize designs and operating factors. Unsaturated and saturated CW designs were used to compare the removal of triazole pesticide, tebuconazole, in unplanted mesocosms and mesocosms planted with five different plant species: Typha latifolia, Phragmites australis, Iris pseudacorus, Juncus effusus and Berula erecta. Tebuconazole removal efficiencies were significantly higher in unsaturated CWs than saturated CWs, showing for the first time the potential of unsaturated CWs to treat tebuconazole contaminated water. An artificial neural network model was demonstrated to provide more accurate predictions of tebuconazole removal than the traditional linear regression model. Also, tebuconazole removal could be fitted an area-based first order kinetics model in both CW designs. The removal rate constants were consistently higher in unsaturated CWs (range of 2.6–10.9 cm d⁻¹) than in saturated CWs (range of 1.7–7.9 cm d⁻¹) and higher in planted CWs (range of 3.1–10.9 cm d⁻¹) than in unplanted CWs (range of 1.7–2.6 cm d⁻¹) for both designs. The low levels of sorption of tebuconazole to the substrate (0.7–2.1%) and plant phytoaccumulation (2.5–12.1%) indicate that the major removal pathways were biodegradation and metabolization inside the plants after plant uptake. The main factors influencing tebuconazole removal in the studied systems were system design, hydraulic loading rate and plant presence. Moreover, tebuconazole removal was positively correlated to dissolved oxygen and all nutrients removal.

Multiple contaminants can affect plant-microbial remediation processes because of their interactive effects on environmental behaviour, bioavailability and plant growth. Recent studies have suggested that arbuscular mycorrhizal fungi (AMF) can facilitate the revegetation of soils co-contaminated with rare earth elements (REEs) and heavy metals. However, little is known regarding the role of AMF in the interaction of REEs and heavy metals. A pot experiment was conducted to evaluate the effects of Claroideoglomus etunicatum on the biomass, nutrient uptake, metal uptake and translocation of maize grown in soils spiked with Lanthanum (La) and Cadmium (Cd). The results indicated that individual and combined applications of La (100 mg kg−1) and Cd (5 mg kg−1) significantly decreased root colonization rates by 22.0%–35.0%. With AMF inoculation, dual-metal treatment significantly increased maize biomass by 26.2% compared to single-metal treatment. Dual-metal treatment significantly increased N, P and K uptake by 20.1%–76.8% compared to single-metal treatment. Dual-metal treatment significantly decreased shoot La concentration by 52.9% compared to single La treatment, whereas AM symbiosis caused a greater decrease of 87.8%. Dual-metal treatment significantly increased shoot and root Cd concentrations by 65.5% and 58.7% compared to single Cd treatment and the La translocation rate by 142.0% compared to single La treatment, whereas no difference was observed between their corresponding treatments with AMF inoculation. Furthermore, AMF had differential effects on the interaction of La and Cd on metal uptake and translocation under the background concentrations of soil metals. Taken together, these results indicated that AMF significantly affected the interaction between La and Cd, depending on metal types and concentrations in soils. These findings promote a further understanding of the contributions of AMF to the phytoremediation of co-contaminated soil.