RESUMO
Combined bioaugmentation inoculants composed of two or more plant growth-promoting bacteria (PGPB) were more effective than single inoculants for plant growth and cadmium (Cd) removal in contaminated soils. However, the principles of consortia construction still need to be discovered. Here, a pot experiment with Cd natural polluted soil was conducted and PGPB consortia with different ecological niches from hyperaccumulator Sedum alfredii Hance were used to compare their effects and mechanisms on plant growth condition, Cd phytoextraction efficiency, soil enzymatic activities, and rhizospheric bacterial community of Brassica juncea L. The results showed that both rhizospheric and endophytic PGPB consortia inoculants promoted plant growth (6.9%-22.1%), facilitated Cd uptake (230.0%-350.0%) of oilseed rape, increased Cd phytoextraction efficiency (343.0%-441.0%), and enhanced soil Cd removal rates (92.0%-144.0%). PGPB consortia inoculants also enhanced soil microbial carbon by 22.2%-50.5%, activated the activities of soil urease and sucrase by 74.7%-158.4% and 8.4%-61.3%, respectively. Simultaneously, PGPB consortia inoculants increased the relative abundance of Flavobacterium, Rhodanobacter, Kosakonia, Pseudomonas and Paraburkholderia at the genus level, which may be beneficial to plant growth promotion and bacterial phytopathogen biocontrol. Although the four PGPB consortia inoculants promoted oilseed growth, amplified Cd phytoextraction, and changed bacterial community structure in rhizosphere soil, their original ecological niches were not a decisive factor for the efficiency of PGPB consortia. therefore, the results enriched the present knowledge regarding the significant roles of PGPB consortia as bioaugmentation agents and preliminarily explored construction principles of effective bioaugmentation inoculants, which will provide insights into the microbial responses to combined inoculation in the Cd-contaminated soils.
Assuntos
Inoculantes Agrícolas , Sedum , Poluentes do Solo , Bactérias , Biodegradação Ambiental , Cádmio/análise , Mostardeira , Rizosfera , Sedum/microbiologia , Solo , Poluentes do Solo/análiseRESUMO
The combination of intercropping and phytoremediation in the remediation of cadmium contaminated soil is an emerging model in recent years, but the results of previous studies are inconsistent. In the field experiment, eggplant was intercropped with hyperaccumulator Sedum alfredii Hance (inoculated or not inoculated with endophytic bacteria) to study the effects of intercropping on vegetable safety production, phytoremediation efficiency of hyperaccumulator and variation of soil available nutrients. The results showed that the intercropping treatment had a negative effect on the growth of eggplant and Sedum, but endophyte SaMR12 alleviated the inhibition of intercropping on plant growth. Intercropping treatment increases the Cd concentration in edible part of eggplant to 1.34 mg/kg compared with eggplant monoculture (1.19 mg/kg). While the application of SaMR12 reduces the Cd concentration of eggplant fruit to 0.95 mg/kg and significantly promotes the Cd uptake by Sedum. What's more surprising is that compared with eggplant monocropping, the content of soil available nitrogen, phosphorus and potassium in the treatment of intercropping with inoculated Sedum increased significantly. And according to the correlation analysis of various indexes of plants and soil, the Cd content of eggplant is negatively correlated with the available phosphorus and potassium in the soil, while the Cd content of Sedum is positively correlated with it, which suggested that the application of phosphorus and potassium fertilizers in this experimental site was beneficial to reduce Cd content in eggplant and improve Cd phytoextraction of Sedum. Therefore, in the daily production of moderately Cd-contaminated soil, intercropping eggplant with Sedum inoculated with endophytic bacteria is an excellent Phytoextraction Coupled with Agro-safe-production (PCA) pattern.
Assuntos
Sedum , Poluentes do Solo , Solanum melongena , Bactérias , Biodegradação Ambiental , Cádmio/análise , Solo , Poluentes do Solo/análise , VerdurasRESUMO
BACKGROUND: Microbes isolated from hyperaccumulating plants have been reported to be effective in achieving higher phytoextraction efficiency. The plant growth-promoting bacteria (PGPB) SaMR12 from the cadmium (Cd)/zinc hyperaccumulator Sedum alfredii Hance could promote the growth of a non-host plant, oilseed rape, under Cd stress. However, the effect of SaMR12 on Brasscia juncea antioxidative response under Cd exposure was still unclear. RESULTS: A hydroponic experiment was conducted to study the effects of Sphingomonas SaMR12 on its non-host plant Brassica juncea (L.) Czern. under four different Cd treatments. The results showed that SaMR12 could colonize and aggregate in the roots and then move to the shoots. SaMR12 inoculation promoted plant growth by up to 71% in aboveground biomass and 81% in root biomass over that of the non-inoculated plants. SaMR12-inoculated plants significantly enhanced root Cd accumulation in the 10 and 20 µM Cd treatments, with 1.72- and 0.86-fold increases, respectively, over that of the non-inoculated plants. SaMR12 inoculation not only decreased shoot hydrogen peroxide (H2O2) content by up to 38% and malondialdehyde (MDA) content by up to 60% but also reduced proline content by 7-30% in shoots and 17-32% in roots compared to the levels in non-inoculated plants. Additionally, SaMR12 inoculation promoted the activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) and facilitated the relative gene expression levels of dehydroascorbate reductase (DHAR) and glutathione reductase (GR) involved in the glutathione (GSH)-ascorbic acid (AsA) cycle. CONCLUSIONS: The results demonstrated that, under Cd stress, SaMR12 inoculation could activate the antioxidative response of B. juncea by decreasing the concentrations of H2O2, MDA and proline, increasing the activities of antioxidative enzymes, and regulating the GSH-AsA cycle. These results provide a theoretical foundation for the potential application of hyperaccumulator endophytic bacteria as remediating agents to improve heavy metal tolerance within non-host plant species, which could further improve phytoextraction efficiency.
Assuntos
Cádmio/efeitos adversos , Endófitos/fisiologia , Mostardeira/efeitos dos fármacos , Poluentes do Solo/efeitos adversos , Sphingomonas/fisiologia , Antioxidantes , Ácido Ascórbico , Expressão Gênica , Glutationa , Mostardeira/genética , Mostardeira/crescimento & desenvolvimento , Mostardeira/microbiologiaRESUMO
Phytoremediation coupled with agroproduction (PCA) model contributes to sustainable agriculture and environmental management. This study investigated the impact of continuous cropping early/late season rice (RR) and Sedum alfredii-rice rotation (SR) on soil physical and chemical properties, as well as their relationships with soil microbial community. In 2022, SR treatment significantly increased pH value and organic matter content by 7 % and 17 %, respectively, compared to the levels in 2020, while RR treatment showed no change. RR treatment resulted in a significant decrease in soil concentrations of Ca, Mg, and K by 18.42 %, 29.01 %, and 7.77 %, respectively. Furthermore, SR treatment saw reductions of 29.62 % in total Cd and 38.30 % in DTPA extractable Cd in the soil. Over the two years, both treatments notably influenced the diversity, structure, and network of the rhizosphere bacterial and fungal communities, which are crucial for nutrient cycling and plant health. Notably, SR treatment exhibited a more complex network compared to RR, suggesting a greater impact on the interconnected systems. Therefore, these findings highlight the potential of Sedum rotation system to rehabilitate contaminated soils while supporting agricultural practices, which is essential for food security and environmental sustainability. This research direction holds promise for future exploration and application in the fields of phytoremediation and agroecology.
RESUMO
Intercropping with hyperaccumulators is believed to be an important and efficient way to achieve simultaneous safe agricultural production and phytoremediation of polluted soils. However, some studies have suggested that this technique might facilitate the uptake of heavy metals by crops. To investigate the effects of intercropping on the heavy metal contents of plants and soil, data from 135 global studies were collected and analyzed by meta-analysis. The results showed that intercropping could significantly reduce the contents of heavy metals in the main plants and soils. Plant species was the main factor that affected plant and soil metal contents in the intercropping system, and the heavy metal content could be significantly reduced when members of the Poaceae and Crassulaceae were used as main plants or when legumes were used as intercropped plants. Among all the intercropped plants, the best one for removing heavy metals from the soil was a Crassulaceae hyperaccumulator. These results not only highlight the main factors affecting intercropping systems but also provide reliable reference information for the practice of safe agricultural production coupled with phytoremediation of heavy metal-contaminated farmland.
Assuntos
Metais Pesados , Poluentes do Solo , Biodegradação Ambiental , Poluentes do Solo/análise , Metais Pesados/análise , Solo , Produtos Agrícolas , Cádmio/análiseRESUMO
Chromium (Cr) is a major pollutant affecting the environment and human health and microbial remediation is considered to be the most promising technology for the restoration of the heavily metal-polluted soil. However, the difference between rhizosphere and endophytic bacteria on the potential of crop safety production in Cr-contaminated farmland is not clearly elucidated. Therefore, eight Cr-tolerant endophytic strains of three species: Serratia (SR-1~2), Lysinebacillus (LB-1~5) and Pseudomonas (PA-1) were isolated from rice and maize. Additionally, one Cr-tolerant strain of Alcaligenes faecalis (AF-1) was isolated from the rhizosphere of maize. A randomized group pot experiment with heavily Cr-contaminated (a total Cr concentration of 1020.18 mg kg-1) paddy clay soil was conducted and the effects of different bacteria on plant growth, absorption and accumulation of Cr in lettuce (Lactuca sativa var. Hort) were compared. The results show that: (i) the addition of SR-2, PA-1 and LB-5 could promote the accumulation of plant fresh weight by 10.3%, 13.5% and 14.2%, respectively; (ii) most of the bacteria could significantly increase the activities of rhizosphere soil catalase and sucrase, among which LB-1 promotes catalase activity by 224.60% and PA-1 increases sucrase activity by 247%; (iii) AF-1, SR-1, LB-1, SR-2, LB-2, LB-3, LB-4 and LB-5 strains could significantly decrease shoot the Cr concentration by 19.2-83.6%. The results reveal that Cr-tolerant bacteria have good potential to reduce shoot Cr concentration at the heavily contaminated soil and endophytic bacteria have the same or even better effects than rhizosphere bacteria; this suggests that bacteria in plants are more ecological friendly than bacteria in soil, thus aiming to safely produce crops in Cr-polluted farmland and alleviate Cr contamination from the food chain.
RESUMO
With the rapid development of industry, chromium (Cr) pollutants accumulate constantly in the soil, causing severe soil Cr pollution problems. Farmland Cr pollution hurts the safety of agricultural production and indirectly affects human health and safety. However, the current situation of Cr pollution in farmland soil and crops has not been detailed enough. In this study, the evaluation of Cr potential risk in soil-crop systems was conducted in a rural area that was affected by industry and historic sewage irrigation. Ten different crops and rhizosphere soils were sampled from four fields. The results showed that Cr contents in farmland soil exceeded the national standard threshold in China (>21.85%), and the Cr content in edible parts of some agricultural products exceeded that too. According to the PCA and relation analysis, the Cr accumulation in edible parts showed a significant correlation with soil Cr contents and available potassium contents. Except for water spinach, the target hazard quotient (THQ) of the other crops was lower than 1.0 but the carcinogenic health risks all exceeded the limits. The carcinogenic risks (CR) of different types of crops are food crops > legume crops > leafy vegetable crops and root-tuber crops. A comprehensive assessment revealed that planting water spinach in this area had the highest potential risk of Cr pollution. This study provided a scientific and reliable approach by integrating soil environmental quality and agricultural product security, which helps evaluate the potential risk of Cr in arable land more efficiently and lays technical guidelines for local agricultural production safety.
RESUMO
Single or combined plant growth-promoting bacteria (PGPB) strains were widely applied as microbial agents in cadmium (Cd) phytoextraction since they could promote plant growth and facilitate Cd uptake. However, the distinct functional effects between single and combined inoculants have not yet been elucidated. In this study, a field experiment was conducted with single, double and triple inoculants to clarify their divergent impacts on plant growth, Cd uptake and accumulation at different growth stages of Brassica juncea L. by three different PGPB strains (Cupriavidus SaCR1, Burkholdria SaMR10 and Sphingomonas SaMR12). The results show that SaCR1 + SaMR10 + SaMR12 combined inoculants were more effective for growth promotion at the bud stage, flowering stage, and mature stage. Single/combined PGPB agents of SaMR12 and SaMR10 were more efficient for Cd uptake promotion. In addition, SaMR10 + SaMR12 combined the inoculants greatly facilitated Cd uptake and accumulation in shoots, and enhanced the straw Cd extraction rates by 156%. Therefore, it is concluded that the application of PGPB inoculants elevated Cd phytoextraction efficiency, and the combined inoculants were more conductive than single inoculants. These results enriched the existing understanding of PGPB agents and provided technical support for the further exploration of PGPB interacting mechanisms strains on plant growth and Cd phytoextraction, which helped establish an efficient plant-microbe combined phytoremediation system and augment the phytoextraction efficiency in Cd-contaminated farmlands.
RESUMO
Cadmium (Cd) exposure is related to a multitude of adverse health outcomes because food crops grown on Cd-polluted soil are widely consumed by the public. The present study investigates the different application techniques of a combined amendment (lime + zeolite + biochar + compost, LZBC) for soil Cd immobilization effect on growth performance, Cd uptake by the second season crops, and soil quality in greenhouse vegetable production (GVP) under a rotation system. Five fruit vegetables were cultivated as the second season crop in the same plots which have been used for pakchoi as the first season crop (with or without LZBC application). The results indicated that LZBC with the consecutive application (T3) promoted crops biomass and fruit yield the most, followed by LZBC with the second crop application (T2) and LZBC with the first crop application (T1). LZBC application showed increasing rhizosphere soil pH and improvement in soil fertility of all crops including available nitrogen, available phosphorus, available potassium, organic matter, and cation exchange capacity. LZBC had positive influences on soluble sugar, soluble protein, and vitamin C in edible parts of 5 vegetables. Cd contents in fruit, shoot, and root of eggplant, pimento, cowpea, and tomato except cucumber were reduced by adding LZBC. As for the economic performance, T3 had the highest output/input ratio in general. Overall, these results demonstrated that T3 was dramatically more effective for minimizing health risk, increasing production, and facilitating sustainable utilization of soil under the Cd-contaminated GVP system.