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Moso bamboo is excellent candidate for cadmium (Cd)/lead (Pb) phytoremediation, while rhizosphere microbiome has significant impact on phytoremediation efficiency of host plant. However, little is known about the rhizosphere bacterial communities of moso bamboo in Cd/Pb contaminated soils. Therefore, this study investigated the assembly patterns and key taxa of rhizosphere bacterial communities of moso bamboo in Cd/Pb polluted and unpolluted soils, by field sampling, chemical analysis, and 16S rRNA gene sequencing. The results indicated α-diversity between Cd/Pb polluted and unpolluted soils showed a similar pattern ( p  > 0.05), while β-diversity was significantly different ( p  < 0.05). The relative abundance analysis indicated α-proteobacteria (37%) and actinobacteria (31%) were dominant in Cd/Pb polluted soils, while γ-proteobacteria (40%) and α-proteobacteria (22%) were dominant in unpolluted soils. Co-occurrence network analysis indicated microbial networks were less complex and more negative in polluted soils than in unpolluted soils. Mantel analysis indicated soil available phosphorus, organic matter, and available Pb were the most important environmental factors affecting microbial community structure. Correlation analysis showed 11 bacterial genera were significantly positively related to Cd/Pb. Overall, this study identified the bacterial community composition of bamboo rhizosphere in responding to Cd/Pb contamination and provides a theoretical basis for microbe-assistant phytoremediation in the future.

Phenylpropanoid biosynthesis plays crucial roles in the adaptation to cadmium (Cd) stress. Nevertheless, few reports have dabbled in physiological mechanisms of such super pathway regulating Cd accumulation in plants. Herein, by integrating transcriptomic, histological and molecular biology approaches, the present study dedicated to clarify molecular mechanism on how rice adapt to Cd stress via phenylpropanoid biosynthesis. Our analysis identified that the enhancement of phenylpropanoid biosynthesis was as a key response to Cd stress. Intriguingly, POD occupied a significant part in this process, with the number of POD related genes accounted for 26/29 of all upregulated genes in phenylpropanoid biosynthesis. We further used SHAM (salicylhydroxamic acid, the POD inhibitor) to validate that POD exhibited a negative correlation with the Cd accumulation in rice tissues, and proposed two intrinsic molecular mechanisms on POD in contributing to Cd detoxification. One strategy was that POD promoted the formation of lignin and CSs both in endodermis and exodermis for intercepting Cd influx. In detail, inhibited POD induced by external addition of SHAM decreased the content of lignin by 50.98-66.65 % and delayed percentage of the D TIP-CS to root length by 39.17-104.51 %. The other strategy was expression of transporter genes involved in Cd uptake, including OsIRT1, OsIRT2, OsZIP1 and OsZIP, negatively regulated by POD. In a word, our findings firstly draws a direct link between POD activity and the Cd accumulation, which is imperative for the breeding of rice with low-Cd-accumulating capacity in the future., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Qi Tao reports financial support was provided by the Science Fund for Distinguished Young Scholars of Sichuan Province. Qi Tao reports financial support was provided by Open Project Program of Key Laboratory of Crop Gene Exploration and Utilization in Southwest China. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Although Cd concentration of grains is generally lower in japonica than in indica subspecies, the effects of root endodermal barriers on the subspecific differences in Cd accumulation in rice (Oryza sativa L.) are poorly understood. Here, we characterized the differences in endodermal differentiation between japonica and indica subspecies and their effects on Cd radial transport. Casparian strips (CSs) and suberin lamellae (SL) in japonica subspecies were initiated at the 6%- 7% and 21%- 27% position from the root tip, respectively, which were 65% and 26% earlier than in indica subspecies, respectively. The lignin/suberin content in japonica subspecies was 47%/42% greater than that in indica subspecies because of the higher expression of lignin/suberin biosynthesis-related genes (OsCASP1, OsPAL, OsCYP86A1 and OsKCS20). Cd exposure induced endodermal plasticity in both subspecies, but the changes in japonica were greater than in indica subspecies. The earlier formation of CSs/SL in japonica subspecies significantly restricted the flow of radial transport tracer to reach the xylem and decreased Cd influx into roots, that is, endodermal barriers inhibited Cd radial transport via both apoplastic and cell-to-cell pathways, thus decreasing the root-to-shoot transport of Cd in japonica subspecies. Our findings are beneficial for the genetic modification of rice with low-Cd-accumulating ability., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Soil Cd pollution is a serious environmental issue associated with human activities. However, the factors determining exogenous Cd dynamics in the soil profile in a complex environment are not well understood. Based on regional observations from 169 soil profiles across the Chengdu Plain, this study explored the key factors controlling Cd accumulation in the soil profile under actual field conditions. Results showed that total soil Cd contents decreased from 0.377 to 0.196 mg kg -1 with increasing soil depth. The effects of phosphate fertilizer rates, road density and precipitation on the difference in total soil Cd content were only observed in topsoil, while agricultural land-use type and topography had no impact. In contrast, significant differences in the total soil Cd content among different parent material types were found in the 0-20, 40-60 and 60-100 cm soil depths. One sample t-tests showed that significant Cd accumulation occurred in the whole soil profile in soils formed from Q4 (Quaternary Holocene) grey alluvium, while soils formed from Q3 (Quaternary Pleistocene) old alluvium and Q4 grey-brown alluvium showed significant Cd accumulation only in the 0-40 cm soil layers. In the topsoil, acid soluble Cd accounted for the largest proportion of the total Cd in soils formed from Q4 grey alluvium, reducible Cd was the main fraction in soils formed from Q4 grey-brown alluvium, while reducible Cd and residual Cd contributed the largest proportion of the total soil Cd in soils formed from Q3 old alluvium. The above results indicated that parent material was the decisive factor determining the magnitudes and depths of exogenous Cd accumulation in the soil profile due to its impacts on the Cd fraction distributions. These findings suggested that the parent material-induced Cd fraction distributions and accumulation should be considered for effectively exploring targeted remediation strategies for Cd pollution., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The recycling of agricultural waste is a global challenge to the sustainable development of agriculture. By using corn stalks, we studied the feasibility of combining anaerobic fermentation and pyrolysis processes to produce both fermentated liquid feed and biologically modified biocharas cadmium adsorbents. Anaerobic ensiling enhanced the biodegradation of corn stalks by increasing crude protein and reducing fiber contents. After 24-h anaerobic fermentation, corn stalks silage was decomposed into the liquid filtrate and non-fermented residue. Fermented liquid feed (FLF) was prepared by storing feed and liquid filtrate (1:4.0, wt/wt) in a closed tank at 20 °C for 4 days, which showed desired properties (pH < 4.5, lactic acid bacteria greater than 9.0 lg cfu g -1 , lactic acid greater than 100 mmol L -1 ). The non-fermented residue was pyrolyzed at 500 °C to prepare biologically modified biochar (BCB24). In comparison with pristine biochar produced from corn stalks (CB), anaerobic ensiling and anaerobic fermentation significantly increased the surface area, oxygen-containing functional groups, as well as mineral components in BCB24. The maximum sorption capacity of Cd(II) for BCB24 was 2.1 times of CB, suggesting that BCB24 is an effective adsorbent for Cd(II) removal from water. Our results indicated that coupling anaerobic fermentation and pyrolysis technology can significantly improve the efficiency of corn stalks recycling., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Agricultural production of Ligusticum chuanxiong Hort. is often affected by heavy metal pollution in soil, especially mixtures of cadmium (Cd) and lead (Pb). We assessed metal-induced phytotoxicity in L. chuanxiong by exposing the plants to soil treated with Cd, Pb, or Cd/Pb mixtures. A combined Cd/Pb treatment alleviated the inhibition in plant growth, photosynthesis, and secondary metabolite generation seen in single-metal exposures in three of the four combinations. Most combined Cd/Pb treatments resulted in preferential uptake of magnesium, copper, and nitrogen in underground plant parts and accumulation of phosphorus and calcium in aboveground plant parts, thereby leading to improvements in photosynthetic potential. Compared with single-metal exposures, combined Cd/Pb treatment significantly decreased the contents of Cd by 16.67%-40.12% and Pb by 10.68%-21.70% in the plant, respectively. At the subcellular level, the Pb presence increased the Cd percentage associated with cell wall from 64.79% to 67.93% in rhizomes and from 32.76% to 45.32% in leaves, while Cd reduced Pb contents by 9.36%-46.39% in the subcellular fractions. A combined Cd/Pb treatment decreased the contents of water- and ethanol-extractable metal forms and increased the contents of acetic acid- and hydrochloric acid-extractable forms. The lower toxic effects of the Cd/Pb mixture in L. chuanxiong were associated with photosynthetic potential, subcellular distribution, the chemical forms of Cd and Pb, and synthesis of secondary metabolites. These findings are useful for plant production strategies in soils contaminated by heavy metals., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Pot-culture experiments were conducted to investigate the potential of microorganism-saponin assisted phytoremediation of cadmium (Cd) and benzo(a)pyrene (B[a]P) co-contaminated soil using Cd-hyperaccumulator Sedum alfredii. Results showed that B[a]P-degrading bacterium (Ochrobactrum intermedium B[a]P-16) inoculation significantly increased root (by 22.1-24.1%) and shoot (by 20.5-23.4%) biomass of S. alfredii, whereas the application of saponin had no effect on the growth of S. alfredii. The saponin solution at 2 g L -1 extracted more Cd and B[a]P than water, saponin enhanced Cd and B[a]P bioavailability in soil and thus promoted their uptake and accumulation in S. alfredii. The activity of B[a]P-16, dehydrogenase and polyphenol oxidase in co-contaminated soil was promoted by growing S. alfredii, and the application of B[a]P-16 and saponins caused a significant (P < 0.05) increase in both enzyme activities. The maximum B[a]P removal rate (82.0%) and Cd phytoextraction rate (19.5%) were obtained by co-application of S. alfredii with B[a]P-16 and saponin. The B[a]P-16 and plant promoted biodegradation were the predominant contributors towards removal of B[a]P from soil. A significant (P < 0.05) synergistic effect of B[a]P-16 and saponin on B[a]P and Cd removal efficiency was observed in this study. It is suggested that planting S. alfredii with application of B[a]P-16 and saponin would be an effective method for phytoremediation of soil co-contaminated with Cd and PAHs., (Copyright © 2019. Published by Elsevier Ltd.)

The root apex is the most active part for water and ions uptake, however, longitudinal alterations in root characteristics along root apex and consequences for metal uptake in hyperaccumulator are poorly understood. Here, we compared cadmium (Cd)-induced longitudinal alterations in root apex of two ecotypes of Sedum alfredii and assess their effects on Cd uptake. Under Cd treatment, cell death began from epidermis to the stele in non-hyperaccumulating ecotype (NHE) over time, and the number of dead cells was significantly higher than that in hyperaccumulating ecotype (HE). Cd-induced the presence of border-like cells (BLCs) surrounding the root tip of NHE prevented Cd from entering roots, however, almost no BLCs were observed in the root tip of in HE. Besides, Cd-treated NHE exhibited 76% and 52% decrease in the proportions of meristematic and elongation zone, respectively, resulting in lower Cd influx and less intensive Cd-fluorescence in these zones, as compared with HE. In the differentiation zone, Cd induced earlier initiation of root hairs (RHs), lower RHs-density, shorter RHs-length, thicker RHs-radius and less trichoblasts in NHE than those in HE. These remarkable variations led to less Cd influx and lower intensity of Cd-fluorescence in RHs of NHE than those of HE. Furthermore, decline in cell wall thickness under Cd exposure resulted in less cell-wall-bond Cd in the cell wall of HE. Therefore, Cd-induced alterations in root characteristics alongside root apex contributed to the difference in Cd uptake and accumulation between two ecotypes of S. alfredii., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Biologically modified biochars derived from digestion residue of corn straw silage at different pyrolysis temperature (300-700 °C) were prepared for removing Cd from water. Compared with the pristine biochar derived from corn straw (CB), transabdominal transformation of corn straw silage (TCB) significantly increased surface area (4.24-56.58 m 2  g -1 ), oxygen-containing functional group (COC, MgO, SiO) and mineral components (CaCO 3 , KCl). The sorption isotherms could be well described by Langmuir model, the kinetic data was best fitted by the Pseudo second order model. The maximum sorption capacity (Qm) obtained from Langmuir model for TCB700 (175.44 mg g -1 ) was 3 times of CB700 (56.82 mg g -1 ). Precipitation with minerals, ion exchange and complexation with oxygen-containing functional groups were the main mechanisms of Cd(II) sorption on TCB. These results imply that biologically modified biochar derived from digestion residue of corn straw silage at ≥600 °C is an effective sorbent for Cd removal from water., (Copyright © 2019 Elsevier B.V. All rights reserved.)

In situ remediation and assessment of sediments contaminated with both antibiotics and heavy metals remains a technological challenge. In this study, MgCl 2 -modified biochar (BCM) was obtained at 500 °C through slow pyrolysis of Thalia dealbata and used for remediation of sediments contaminated by sulfamethoxazole (SMX) and Cd. The BCM showed greater surface area (110.6 m 2  g -1 ) than pristine biochar (BC, 7.1 m 2  g -1 ). The SMX sorption data were well described by Freundlich model while Langmuir model was better for the Cd 2+ sorption data. The addition of 5.0% BCM significantly increased the sorption of SMX (by 50.8-58.6%) and Cd (by 24.2-25.6%) on sediments in both single and binary systems as compared with 5.0% BC. SMX sorption in sediments was significantly improved by addition of Cd 2+ , whereas SMX has no influence on Cd sorption on sediments. The addition of BCM distinctly decreased both SMX (by 51.4-87.2%) and Cd concentrations (by 56.2-91.3%) in overlying water, as well as in TCLP extracts (by 55.6-86.1% and 58.2-91.9% for SMX and Cd, respectively), as compared with sediments without biochar. Both germination rate and root length of pakchoi increased with increasing doses of BCM in contaminated sediments, 5.0% BCM showed greater promotion on pakchoi growth than 5.0% BC. Overall, BCM in the sediments does not only decrease the bioavailability of SMX and Cd, but it also diminishes the phytotoxicity, and thereby shows great application potential for in situ remediation of sediments polluted with antibiotics and heavy metals., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Strategies to reduce cadmium (Cd) in rice grain, below concentrations that represent serious human health concerns, require that the mechanisms of Cd distribution and accumulation within rice plants be established. Here, a comprehensive hydroponic experiment was performed to investigate the differences in the Cd uptake, chelation and compartmentalization between high (D83B) and low (D62B) Cd-accumulation cultivars contrasting in Cd accumulation in order to establish the roles of these processes in limiting Cd translocation from root to shoot. D83B showed 3-fold higher Cd accumulation in the shoots than the cultivar D62B. However, a short-term Cd uptake experiment showed more Cd uptake by D62B than by D83B. The distribution of Cd in roots and shoots differed significantly. D83B translocated 38% of total Cd taken up to the shoots, whereas D62B retained most of the Cd in the roots. D62B had higher amounts of non-protein thiols (NPTs) and glutathione (GSH) than D83B. The NPT and Cd distribution ratio (CDR) in the anionic form in the roots of D62B increased gradually as Cd concentration increased. In D83B, in contrast, levels of CDR in the cationic form increased significantly from 22.10 to 43.37%, while NPT only increased slightly. Furthermore, the percentage of Cd ions retained in thiol-rich peptides, especially in the HMW complexes, was significantly higher in D62B compared with D83B. However, D83B possessed a greater proportion of potentially mobile (cationic) Cd in the roots and showed superior Cd translocation from root to shoot. Taken as a whole, the results presented in this study revealed that Cd chelation, compartmentalization and adsorption contribute to the Cd retention in roots.

Semi-agricultural ecosystems in peri-urban areas are susceptible to contamination. The spatial distribution and influencing factors of such pollution are unclear and poorly constrained in many areas worldwide. Therefore, studying the problems of soil pollution in peri-urban areas is critical for environmental management and agricultural production. In this paper, with cadmium (Cd) as the target pollutant, the spatiotemporal variations of soil cadmium pollution and the relative importance of the affecting factors were analyzed at a peri-urban area from the Jingyang District, Sichuan, China. Statistical results showed that the farmland in the study area could be considered moderately soil Cd-polluted, under the dual influence of natural factors and human activity. In particular, the soil Cd concentration in Tianyuan and Bajiaojing exceeded 0.5 mg kg -1 , for intensive industrial enterprises are distributed in these areas. Correspondingly, the geoaccumulation index also showed that the contamination of Cd in this area was moderately polluted. Moreover, the ecological risk index was 80% in the study area, indicating that the soil Cd pollution potential risk was moderate to high. High geological background values (soil Cd = 0.29 mg kg -1 ), river migration, industrial enterprises, and traffic significantly influenced soil Cd pollution, with natural geological factors playing greater roles. The significant horizontal-spatial effective distances away from Shiting River, Deyang-Aba Highway, and chemical plants were 200, 400, and 100 m, respectively. These results will be useful in guiding farmland cultivation and pollution remediation effectively in the peri-urban areas.

Heavy metal pollution of the soil affects the environment and human health. Masson pine is a good candidate for phytoremediation of heavy metal in mining areas. Microorganisms in the rhizosphere can help with the accumulation of heavy metal in host plants. However, studies on its rhizosphere bacterial communities under heavy metal pollution are still limited. Therefore, in this study, the chemical and bacterial characteristics of Masson pine rhizosphere under four different levels of heavy metal pollution were investigated using 16 S rRNA gene sequencing, soil chemistry and analysis of plant enzyme activities. The results showed that soil heavy metal content, plant oxidative stress and microbial diversity damage were lower the farther they were from the mine dump. The co-occurrence network relationship of slightly polluted soils (C1 and C2) was more complicated than that of highly polluted soils (C3 and C4). Relative abundance analysis indicated Sphingomonas and Pseudolabrys were more abundant in slightly polluted soils (C1 and C2), while Gaiella and Haliangium were more abundant in highly polluted soils (C3 and C4). LEfSe analysis indicated Burkholderiaceae, Xanthobacteraceae, Gemmatimonadaceae, Gaiellaceae were significantly enriched in C1 to C4 site, respectively. Mantel analysis showed that available cadmium (Cd) contents of soil was the most important factor influencing the bacterial community assembly. Correlation analysis showed that eight bacterial genus were significantly positively associated with soil available Cd content. To the best of our knowledge, this is the first study to investigate the rhizospheric bacterial community of Masson pine trees under different degrees of heavy metal contamination, which lays the foundation for beneficial bacteria-based phytoremediation using Masson pines in the future. [Display omitted] • Sphingomonas, Bradyrhizobium and Haliangium were dominated in pine rhizosphere. • Bacterial network of HM polluted soil was simpler than that of clean soil. • Gaiella and Haliangium were representative taxa in HM polluted soils. • Soil available Cd was the most important factor influencing bacterial community. • Plant antioxidant was positively correlated with soil heavy metals. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) is a key phytohormone underlying plant resistance to toxic metals. However, regulatory effects of ABA on apoplastic transport in roots and consequences for uptake of metal ions are poorly understood. Here, we demonstrate how ABA regulates development of apoplastic barriers in roots of two ecotypes of Sedum alfredii and assess effects on cadmium (Cd) uptake. Under Cd treatment, increased endogenous ABA level was detected in roots of nonhyperaccumulating ecotype (NHE) due to up‐regulated expressions of ABA biosynthesis genes (SaABA2, SaNCED), but no change was observed in hyperaccumulating ecotype (HE). Simultaneously, endodermal Casparian strips (CSs) and suberin lamellae (SL) were deposited closer to root tips of NHE compared with HE. Interestingly, the vessel‐to‐CSs overlap was identified as an ABA‐driven anatomical trait. Results of correlation analyses and exogenous applications of ABA/Abamine indicate that ABA regulates development of both types of apoplastic barriers through promoting activities of phenylalanine ammonialyase, peroxidase, and expressions of suberin‐related genes (SaCYP86A1, SaGPAT5, and SaKCS20). Using scanning ion‐selected electrode technique and PTS tracer confirmed that ABA‐promoted deposition of CSs and SL significantly reduced Cd entrance into root stele. Therefore, maintenance of low ABA levels in HE minimized deposition of apoplastic barriers and allowed maximization of Cd uptake via apoplastic pathway. Abscisic acid regulated the development of endodermal Casparian strips (CSs) and suberin lamellae (SL) in roots of S. alfredii exposed to Cd. Maintenance of low ABA levels in hyperaccumulating ecotype minimized deposition of CSs/SL and allowed maximization of Cd uptake via apoplastic pathway. [ABSTRACT FROM AUTHOR]

Ferromanganese oxide biochar composite (FMBC) is an efficient remediation material for cadmium -contaminated soils. However, the effect of FMBC under varied water managements on the remediation of Cd-polluted soil is unclear. In this study, we conducted both incubation and field experiments to investigate the combined effects of corn-stover-derived biochar modified with ferromanganese on the immobilization and uptake of Cd by rice under continuous aerobic (A), aerobic-flooded (AF), and flooded-aerobic (FA) water management regimes. The results showed that loading iron-manganese significantly increased the maximum sorption capacity (Q m) of Cd on FMBC (50.46 mg g−1) due to increased surface area, as compared to the pristine biochar (BC, 31.36 mg g−1). The results revealed that soil Eh and pH were significantly affected by FMBC and it's synergistic application with different water regimes, thus causing significant differences in the concentrations of DTPA-extractable Cd under different treatments. The lowest DTPA-extractable Cd content (0.28–0.46 mg−1) was observed in the treatment with FMBC (2.5 %) combined FA water amendment, which reduced the content of available Cd in soil by 2.63–28.4 %. Moreover, the treatments with FMBC-FA resulted the proportion of residual Cd increased by 22.2 % compared to the control. Variations in the content and fraction of Cd had a significant influence on its accumulation in the rice grains. The FMBC-FA treatments reduced the Cd concentration in roots, shoots and grains by 37.97 %, 33.98 %, and 53.66 %, respectively, when compared with the control. Predominantly because of the reduction in Cd biological toxicity and the improved soil nutrient content, the combined application increased the biomass and yield of rice to some extent. Taken together, the combination of the Fe-Mn modified biochar and flooded-aerobic water management may potentially be applied in Cd-polluted soil to mitigate the impacts of Cd on rice production. [Display omitted] • Iron-manganese biochar (FMBC) remarkably increased the sorption capacity of Cd(II). • FMBC combined flooded-aerobic mode (FA) improved soil nutrients with incubation time. • FA facilitated the release of Fe2+/Mn2+ from FMBC and decreased Cd availability. • FMBC-FA reduced Cd accumulation in rice grains statistically under field condition. • An optimized coupling strategy for minimizing Cd pollution is proposed. [ABSTRACT FROM AUTHOR]

Abstract\nNOVELTY STATEMENTRice is the staple food for 1/3 of the world’s population, but soil pollution with cadmium (Cd) is harmful to rice production and human health. Therefore, how to reduce the Cd content in rice grains is a hot topic worldwide. However, so far, little is known about Cd remediation technologies for paddy soils from the perspective of patents. Therefore, a meta-analysis was performed to assess the effects of measures based on 1402 observations from 336 patents from 2011 to 2021. The spatio-temporal analysis showed that the number of patents was positively related to the general economic development of the country, but hardly related to the regional economy or the level of provincal Cd pollution. The meta-analysis showed that the overall effect of Cd reduction was slightly higher for combined technologies (59%) than for single technologies (57%). Among all technology classifications, soil applications, which are mainly based on nutritional elements, were the most commonly used technology that could reduce the Cd content in rice grains by 57%. The plant biotechnology was the most effective and could reduce Cd content in rice grains by 76%. Further analysis showed that macronutrients (calcium, phosphorus, and sulfur) were preferred in soil amendments, while micronutrients (silicon, zinc, and selenium) were preferred in foliar amendments. NRAMP5 and HMA3 were the most important genes for manipulating Cd uptake in rice, while Bacillus and Pseudomonas were the most important bacterial taxa for bioremediation of Cd. Overall, this study compiled data on Cd remediation of paddy soil from 10 years of Chinese patents, providing a theoretical basis for better production of low Cd crops and protection of human health.Patents are an indicator and promoter of theoretical innovation and technological improvement. However, little is known about Cd remediation technologies for paddy soils and rice grains from the perspective of patents. In this study, the first dataset of soil Cd remediation and rice safety production measures from the Chinese patents in the past 10 years was established. Then it evaluated the effect of each measure using meta-analysis and pointed out the future direction of research to find better solutions for Cd remediation. [ABSTRACT FROM AUTHOR]

Rice (Oryza sativa) is one of the major cereal crops and takes up cadmium (Cd) more readily than other crops. Understanding the mechanism of Cd uptake and defense in rice can help us avoid Cd in the food chain. However, studies comparing Cd uptake, toxicity, and detoxification mechanisms of leaf and root Cd exposure at the morphological, physiological, and transcriptional levels are still lacking. Therefore, experiments were conducted in this study and found that root Cd exposure resulted in more severe oxidative and photosynthetic damage, lower plant biomass, higher Cd accumulation, and transcriptional changes in rice than leaf Cd exposure. The activation of phenylpropanoids biosynthesis in both root and leaf tissues under different Cd exposure routes suggests that increased lignin is the response mechanism of rice under Cd stress. Moreover, the roots of rice are more sensitive to Cd stress and their adaptation responses are more pronounced than those of leaves. Quantitative PCR revealed that OsPOX , OsCAD , OsPAL and OsCCR play important roles in the response to Cd stress, which further emphasize the importance of lignin. Therefore, this study provides theoretical evidence for future chemical and genetic regulation of lignin biosynthesis in crop plants to reduce Cd accumulation. [Display omitted] • Cd uptake of rice is higher in root exposure than leaf exposure. • Cd phytotoxicity of rice is stronger in root exposure than leaf exposure. • Transcriptome responses is more pronounced in root exposure than leaf exposure. • Phenylpropanoid biosynthesis pathway is activated under Cd stress. • Lignin and cell wall biosynthesis is enhanced under Cd stress. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) is readily absorbed by rice and enters the food chain, posing a health risk to humans. A better understanding of the mechanisms of Cd-induced responses in rice will help in developing solutions to reduce Cd uptake in rice. Therefore, this research attempted to reveal the detoxification mechanisms of rice in response to Cd through physiological, transcriptomic and molecular approaches. The results showed that Cd stress restricted rice growth, led to Cd accumulation and H 2 O 2 production, and resulted cell death. Transcriptomic sequencing revealed glutathione and phenylpropanoid were the major metabolic pathways under Cd stress. Physiological studies showed that antioxidant enzyme activities, glutathione and lignin contents were significantly increased under Cd stress. In response to Cd stress, q-PCR results showed that genes related to lignin and glutathione biosynthesis were upregulated, whereas metal transporter genes were downregulated. Further pot experiment with rice cultivars with increased and decreased lignin content confirmed the causal relationship between increased lignin and reduced Cd in rice. This study provides a comprehensive understanding of lignin-mediated detoxification mechanism in rice under Cd stress and explains the function of lignin in production of low-Cd rice to ensure human health and food safety. [Display omitted] • Glutathione and phenylpropanoid pathways were active under Cd stress. • Antioxidant, GSH and lignin contents were increased under Cd stress. • Cell wall of rice root was thickened under Cd stress. • The expressions of OsIRT1, OsNRAMP5 and OsHMA2 were down-regulated. • Enhanced lignin content lead to higher yield and lower Cd in rice grain. [ABSTRACT FROM AUTHOR]

Abscisic acid (ABA) play a crucial role in plant acclimation to heavy-metals stresses. Nevertheless, the effects of ABA on long-distance transport and its consequences for cadmium (Cd) accumulation are insufficiently understood. Here, we investigated the effects of ABA on the development of the whole-plant water transport pathway and implications for Cd uptake and transport to the shoot of Sedum alfredii. Exposure to Cd stimulated the production of endogenous ABA levels in the non-hyperaccumulating ecotype (NHE), but not in the hyperaccumulating ecotype (HE). Increased ABA levels in NHE significantly reduced aquaporin expressions in roots, the number of xylem vessel in stem, dimensions and densities of stomata in leaves, but induced leaf osmotic adjustment. Furthermore, the ABA-driven modifications in NHE plants showed typically higher sensitivity to ABA content in leaves compared to HE, illustrating ecotype-specific responses to ABA level. In NHE, the ABA-mediated modifications primarily affected the xylem transport of Cd ions and, at the cost of considerable water delivery limitations, significantly reduced delivery of Cd ions to shoots. In contrast, maintenance of low ABA levels in HE failed to t limit transpiration rates and maximized Cd accumulation in shoots. Our results demonstrated that ABA regulates Cd hyperaccumulation of S. alfredii through specific modifications in the water transport continuum. • Differences in ABA synthesis drive ability of S. alfredii to accumulate Cd. • Cd induced different ABA production in different ecotype of S. alfredii. • ABA regulates development of the whole plant water transport pathway of S. alfredii. • Elevated ABA level hindered Cd accumulation via impaired water status in NHE. • Maintenance of minimum ABA level promoted uptake and delivery of water and Cd in HE. [ABSTRACT FROM AUTHOR]

• About 2.30% of the assimilated 13C was incorporated into organic acid in rhizosphere of S. alfredii. • Tartaric acid is the unique root exudate from HE S. alfredii. • Tartaric acid was mainly distributed within the range of rhizosphere 0–6 mm. • Tartaric acid is highly efficient in Cd solubilization via the formation of soluble Cd-Tartrate complexes. • Tartaric acid enhanced Cd uptake in HE S. alfredii. Low molecular weight organic acids (LMWOA) involved in heavy metal tolerance, translocation, and accumulation in plants. However, underlying mechanism of LMWOA secretion in metal mobilization and uptake in hyperaccumulator still need to be identified. In this study, a 13C labeling rhizobox was designed to investigate the composition and distribution of LMWOA in the rhizosphere of S. alfredii. The result showed that about 2.30%, 2.25% and 2.35% of the assimilated 13C was incorporated into oxalic acid, malic acid, and tartaric acid in rhizosphere of S. alfredii after 13CO 2 assimilation, respectively. Oxalic acid, malic acid, and tartaric acid were the predominant LMWOA in rhizosphere soil solution of hyperaccumulating ecotype (HE) S. alfredii , however, almost no tartaric acid was detected for non-hyperaccumulating ecotype (NHE). Tartaric acid was identified as the unique root exudate from HE S. alfredii which was mainly distributed within the range of rhizosphere 0–6 mm. Tartaric acid significantly increased the solubility of four Cd minerals. HE S. alfredii treated with tartrate + CdCO 3 had higher Cd contents and larger biomass than CdCO 3 treatment. Cadmium accumulation in HE S. alfredii was promoted by the exudation of tartaric acid, which was highly efficient in Cd solubilization due to the formation of soluble Cd-tartrate complexes. [ABSTRACT FROM AUTHOR]