Since the urbanization and industrialization are wildly spread in recent decades, the concentration of Zn in soil has increased in various regions. Although the interactions between P and Zn has long been recognized, the effect of high level of Zn on P uptake, translocation and distribution in rice and its molecular mechanism are not fully understood. In this study, we conducted both hydroponic culture and field trial with different combined applications of P and Zn to analyze the rice growth and yield, the uptake, translocation and distribution of P and Zn, as well as the P- and Zn-related gene expression levels. Our results showed that high level of Zn decreased the rice biomass and yield production, and inhibited the root-to-shoot translocation and distribution of P into new leaves by down-regulating P transporter genes OsPT2 and OsPT8 in shoot, which was controlled by OsPHR2-OsmiR399-OsPHO2 module. High Zn supply triggered P starvation signal in root, thereafter increased the activities of both root-endogenous and -secreted acid phosphatase to release more Pi, and induced the expression OsPT2 and OsPT8 to uptake more P for plant growth. On the other hand, high level of P significantly decreased the Zn concentrations in both root and shoot, and the root uptake ability of Zn through altering the expression levels of OsZIPs, which were further confirmed by the P high-accumulated mutant osnla1-2 and OsPHR2-OE transgenic plant. Taken together, we revealed the physiological and molecular mechanisms of P–Zn interactions, and proposed a working model of the cross-talk between P and Zn in rice plants. Our results also indicated that appropriate application of P fertilizer is an effective strategy to reduce rice uptake of excessive Zn when grown in Zn-contaminated soil.

Earthworms and arbuscular mycorrhizal fungi (AMF) act synergistically in the rhizosphere and may increase host plant tolerance to Cd. However, mechanisms by which earthworm-AMF-plant partnerships counteract Cd phytotoxicity are unknown. Thus, we evaluated individual and interactive effects of these soil organisms on photosynthesis, antioxidant capacity, and essential nutrient uptake by Solanum nigrum, as well as on soil quality following Cd exposure (0–120 mg kg⁻¹). Decreases in biomass and photosynthetic activity, as well as nutrient imbalances were observed in Cd-stressed plants; however, the addition of AMF and earthworms reversed these effects. Cd exposure increased superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities, whereas inoculation with Rhizophagus intraradices decreased those. Soil enzymatic activity decreased by 15–60% with increasing Cd concentrations. However, Cd-mediated toxicity was partially reversed by soil organisms. Earthworms and AMF ameliorated soil quality based on soil enzyme activity. At 120 mg kg⁻¹ Cd, the urease, catalase, and acid phosphatase activities were 1.6-, 1.4-, and 1.2-fold higher, respectively, in soils co-incubated with earthworms and AMF than in uninoculated soil. Cd inhibited shoot Fe and Ca phytoaccumulation, whereas AMF and earthworms normalized the status of essential elements in plants. Cd detoxification by earthworm-AMF-S. nigrum symbiosis was manifested by increases in plant biomass accumulation (22–117%), chlorophyll content (17–63%), antioxidant levels (SOD 10–18%, POD 9–25%, total polyphenols 17–22%, flavonoids 15–29%, and glutathione 7–61%). It also ameliorated the photosynthetic capacity, and macro- and micronutrient statuses of plants; markedly reduced the levels of malondialdehyde (20–27%), superoxide anion (29–36%), and hydrogen peroxide (19–30%); and upregulated the transcription level of FeSOD. Thus, the combined action of earthworms and AMF feasibly enhances metal tolerance of hyperaccumulating plants and improves the quality of polluted soil.

The interactive effects of elevated atmospheric CO₂ and nanoparticles (NPs) on the structure and function of soil bacterial community remain unknown. Here we compared the impacts of CeO₂ (nCeO₂) and Cr₂O₃ (nCr₂O₃) nanoparticles on the taxonomic compositions and functional attributes of bacterial communities under elevated CO₂ (eCO₂). The stimulated enzyme activities (dehydrogenase, acid phosphatase and urease), increased microbial biomass carbon (MBC), and higher bacterial alpha-diversity were observed under the combined effects of eCO₂ and NPs compared to the single NP treatment, indicating eCO₂ could mitigate the adverse effect of NPs on soil microorganisms. NPs and eCO₂ are important factors influencing the alpha- and beta-diversity (17% and 18% of variations were explained) as well as functional profile (20% and 26% of variations were explained) of bacterial communities. Rising CO₂ level promoted the resilience of NP-resistant bacterial populations, primarily the members of Alphaproteobacteria, Gammaproteobacteria and Bacteroidia, which are also characterized by the fast carbon use capability. Moreover, the significantly (P < 0.05) higher metabolic quotient (qCO₂), reduced available carbon and overrepresented carbon metabolism genes at eCO₂vs. ambient CO₂ (aCO₂) indicate the acceleration of available carbon turnover in NP-exposed soils. Correlation analysis revealed that mitigation of NPs toxicity by eCO₂ could be attributed to the remarkable decline of bioavailable metals disassociated from NPs and available carbon level, as well as promotion of the rapid carbon-metabolizing microbes. Our study pointed out the positive role of eCO₂ in alleviating the adverse effect of NPs on microbiological soil environment, and results can serve as important basis in establishing guidelines for lowering the ecotoxicity of NPs.

Cyanobacterial blooms cause potential risk to submerged macrophytes and biofilms in eutrophic environments. This pilot-scale study investigated the growth, oxidative responses, and detoxification activity of aquatic plants in response to cyanobacterial blooms under different phosphorus concentrations. Variations of extracellular polymeric substances (EPSs) and microbial community composition were also assessed. Results showed that the biomass of Vallisneria natans increased with exposure to cyanobacterial blooms at higher phosphorous concentrations (P > 0.2 mg L⁻¹). The amount of microcystin compounds (MC-LR) released into the water and the accumulation of MC-LR into both plant tissue and biofilms changed according to the phosphorus concentration. Furthermore, a certain degree of oxidative stress was induced in the plants, as evidenced by increased activity of superoxide dismutase, catalase, and peroxidase, as well as increased malondialdehyde concentrations; significant differences were also seen in acid phosphatase and glutathione S-transferase activities, as well as in glutathione concentrations. Together, these responses indicate potential mechanisms of MC-LR detoxification. Broader α-D-glucopyranose polysaccharides (PS) increased with increasing phosphorous and aggregated into clusters in biofilm EPS in response to the cyanobacterial blooms. In addition, alterations were seen in the abundance and structure of the microbial communities present in exposed biofilms. These results demonstrate that cyanobacterial blooms under different concentrations of phosphorus can induce differential responses, which can have a significant impact on aquatic ecosystems.

Glyphosate (GLY) is one of the most used herbicide worldwide. Considering that information concerning the impact of GLY on bivalves is scarce, in this study we evaluated for the first time the effects of environmentally realistic concentrations of GLY (10, 100 and 1000 μg/L) to the mussel Mytilus galloprovincialis. Mussels were exposed for 7, 14 and 21 days and several biomarkers were measured in haemocytes/haemolymph (total haemocyte counts, haemocyte diameter and volume, haemolymph pH, haemolymph lactate dehydrogenase activity, haemocyte lysate lysozyme and acid phosphatase activities), as well as in gills and digestive gland (antioxidant enzyme and acetylcholinesterase activities). The concentrations of GLY and its main metabolite aminomethylphosphonic acid in the experimental tanks were also measured. The MANOVA analysis demonstrated that the experimental variables considered (exposure concentration, exposure duration, and their interaction) affected significantly biomarker responses. In addition, the two-way ANOVA analysis indicated that GLY was able to affect most of the cellular parameters measured, whereas antioxidant enzyme activities resulted to be influenced moderately. Interestingly, exposure to GLY reduced significantly acetylcholinesterase activity in gills. Although preliminary, the results of this study demonstrated that GLY can affect both cellular and biochemical parameters in mussels, highlighting a potential risk for aquatic invertebrates.

Antibiotics have been widely used in human and veterinary medicine to both treat and prevent disease. Due to their high water solubility and low bioavailability, many antibiotic residues have been found in aquatic environments. Fish are an indispensable link between the environmental pollution and human health. However, the chronic effects of environmental concentrations of antibiotics in fish have not been thoroughly investigated. Sulfamethoxazole (SMX) and oxytetracycline (OTC) are frequently detected in aquatic environments. In this study, zebrafish were exposed to SMX (260 ng/L) and OTC (420 ng/L) for a six-week period. Results indicated that exposure to antibiotics did not influence weight gain of fish but increased the metabolic rate and caused higher mortality when treated fish were challenged with Aeromonas hydrophila. Furthermore, exposure to antibiotics in water resulted in a significant decrease in intestinal goblet cell numbers, alkaline phosphatase (AKP), acid phosphatase (ACP) activities, and the anti-oxidant response while there was a significant increase in expression of inflammatory factors. Antibiotic exposure also disturbed the intestinal microbiota in the OTC-exposed group. Our results indicated that environmental antibiotic concentrations can impair the gut health of zebrafish. The potential health risk of antibiotic residues in water should be evaluated in the future.

Soil Cd and Zn contamination has become a serious environmental problem. This work explored the performance of wood vinegar (WV) in enhancing the phytoextraction of Cd/Zn by hyperaccumulator Sedum alfredii Hance. Rhizosphere chemical properties, enzyme activities and bacterial community were analyzed to determine the mechanisms of metal accumulation in this process. Results demonstrated that, after 120 days growth, different times dilution of WV increased the shoot biomass of S. alfredii by 85.2%–148%. In addition, WV application significantly increased soil available Cd and Zn by lowing soil pH, which facilitated plant uptake. The optimal Cd and Zn phytoextraction occurred from the 100 times diluted WV (D100), which increased the Cd and Zn extraction by 188% and 164%, compared to CK. The 100 and 50 times diluted WV significantly increased soil total and available carbon, nitrogen and phosphorus, and enhancing enzyme activities of urease, acid phosphatase, invertase and protease by 10.1–21.4%, 29.1–42.7%,12.2–38.3% and 26.8–85.7%, respectively, compared to CK. High-throughput sequencing revealed that the D 100 significantly increased the bacterial diversity compared to CK. Soil bacterial compositions at phylum, family and genera level were changed by WV addition. Compared to CK, WV application increased the relative abundances of genus with plant growth promotion and metal mobilization function such as, Bacillus, Gemmatimonas, Streptomyces, Sphingomonas and Polycyclovorans, which was positively correlated to biomass, Cd/Zn concentrations and extractions by S. alfredii. Structural equation modeling analysis showed that, soil chemical properties, enzyme activities and bacterial abundance directly or indirectly contributed to the biomass promotion, Cd, and Zn extraction by S. alfredii. To sum up, WV improved phytoextraction efficiency by enhancing plant growth, Cd and Zn extraction and increasing soil nutrients, enzyme activities, and modifying bacterial community.

In situ remediation technology applied aims to not only decrease cadmium (Cd) and arsenic (As) uptake by rice but also improve soil health and rice quality in contaminated paddy soils. Here the effects of a combined amendment, consisting of limestone, iron powder, silicon fertilizer, and calcium-magnesium-phosphate fertilizer, with three application rates (0, 450, and 900 g m⁻²) on soil health, rice root system, and brown rice quality were compared in moderately versus highly Cd and As co-contaminated paddy fields. After the amendment application, soil pH, cation exchange capacity, four kinds of soil enzyme activities increased (sucrase, urease, acid phosphatase, and catalase), and concentrations of leached Cd/As decreased, as measured by the DTPA (diethylene triamine pentaacetic acid) and TCLP (toxicity characteristic leaching procedure). Changes in the above soil indicators promoted soil health. In both fields, the dithionite-citrate-bicarbonate (DCB)-Fe and DCB-Mn concentration in iron plaque increased and root length became longer. Changes in the above root system indicators reduced the root system's absorption of Cd and As but increased that of nutrients. Under 900 g m⁻² treatment, the Cd concentration in brown rice of two sites decreased by 55.8% and 28.9%, likewise inorganic As (iAs) decreased by 50.0% and 21.1%, whereas essential amino acids increased by 20.4% and 20.0%, respectively. Furthermore, the Cd and iAs concentrations in brown rice were <0.2 mg kg⁻¹ (maximum contaminant level of Cd and iAs in the Chinese National Food Safety Standards GB2762-2017 for brown rice) under the 900 g m⁻² in the moderately contaminated field. These results suggest the combined amendment can improve soil health and brown rice quality in the moderately and highly Cd- and As-co-contaminated paddy soils, offering potential eco-friendly and efficient remediation material for applications in such polluted paddy soils.

Arsenite [As(III)] toxicity causes impeded growth, inadequate productivity of plants and toxicity through the food chain. Using various chemical residues for priming is one of the approaches in conferring arsenic tolerance in crops. We investigated the mechanism of abscisic acid (ABA)-induced As(III) tolerance in rice genotypes (cv. Swarna and Swarna Sub1) pretreated with 10 μM of ABA for 24 h and transferred into 0, 25 and 50 μM arsenic for 10 days. Plants showed a dose-dependent bioaccumulation of As(III), oxidative stress indicators like superoxide, hydrogen peroxide, thiobarbituric acid reactive substances and the activity of lipoxygenase. As(III) had disrupted cellular redox that reflecting growth indices like net assimilation rate, relative growth rate, specific leaf weight, leaf mass ratio, relative water content, proline, delta-1-pyrroline-5-carboxylate synthetase and electrolyte leakage. ABA priming was more protective in cv. Swarna Sub1 than Swarna for retrieval of total glutathione pool, non-protein thiols, cysteine, phytochelatin and glutathione reductase. Phosphate metabolisms were significantly curtailed irrespective of genotypes where ABA had moderated phosphate uptake and its metabolizing enzymes like acid phosphatase, alkaline phosphatase and H⁺/ATPase. Rice seedlings had regulated antioxidative potential with the varied polymorphic expression of those enzymes markedly with antioxidative enzymes. The results have given the possible cellular and physiological traits those may interact with ABA priming in the establishment of plant tolerance with As(III) over accumulation and, thereby, its amelioration for oxidative damages. Finally, cv. Swarna Sub1 was identified as a rice genotype as a candidate for breeding program for sustainability against As(III) stress with cellular and physiological traits serving better for selection pressure.

A pot experiment was carried out on brown soil polluted by dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) to investigate the effects of biochar (BC) derived from corn straw and Fe–Mn oxide modified biochar composites (FMBC) on the bioavailability of DBP and DEHP, as well as ecosystem responses in rhizosphere soil after wheat ripening. The results indicate that the application of BC and FMBC significantly increases soil organic matter, pH, available nitrogen (AN), Olsen phosphorus, and available potassium (AK); reduces the bioavailability of DBP and DEHP; enhances the activities of dehydrogenase, urease, protease, β-glucosidase, and polyphenol oxidase; and decreases acid phosphatase activity. No changes in richness and diversity, which were measured by Illumina MiSeq sequencing, were observed following BC and FMBC application. The bacterial community structure and composition varied with DBP/DEHP concentrations and BC/FMBC additions in a nonsystematic way and no significant trends were observed. In addition, FMBC exhibited better performance in increasing soil properties and decreasing the bioavailability of DBP and DEHP compared with BC. Hence, the FMBC amendment may be a promising way of developing sustainable agricultural environmental management.