Incubation experiments were conducted to investigate the influencing factors of pH variation in different paddy soils during submerging/draining alternation and the relationship between pH buffering ...capacity (pHBC) and Cd speciation in ten paddy soils developed from different parent materials (including 8 acid paddy soils and 2 alkaline paddy soils). The soil pHBC and the changes in soil pH, Eh, Fe2+, Mn2+, SO42- and Cd speciation were determined. The results showed that there was a significant positive correlation between cation exchange capacity (CEC) and pHBC of these paddy soils, indicating that soil CEC is a key factor affecting the pHBC of paddy soils. The contribution of Fe(III) oxide reduction to H+ consumption is far greater than the reduction of Mn(IV)/Mn(III) oxides and SO42- during the submerging. For example, the contribution of the reduction of manganese oxides, SO42- and iron oxides to H+ consumption in the paddy soils from Anthrosol at 15 d submerging was 1.2%, 11.6% and 87.2%, respectively. This confirms that the reduction of Fe(III) oxides plays a leading role in increasing soil pH. Importantly, we noticed that during submerging, soil pH was increased and resulted in the content of available Cd in soils being reduced. This was due to the transformation of Cd to less active forms. Also, there was a significant positive correlation between the change rate of available Cd, the percentage of acid extractable Cd and pH variation. This suggests that the variation in soil pH was responsible for the transformation of Cd speciation. In addition, the change rate of available Cd and the percentage of acid extractable Cd concentration were significantly negatively correlated with soil pHBC. The soil with higher pHBC experienced less pH change, and thus the change rate of available Cd and the percentage of acid extractable Cd concentration were less for the soil. The results of this study can provide a basis for the remediation of Cd-contaminated acidic paddy soils.
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•Soil CEC is the main factor affecting paddy soil pH buffering capacity (pHBC).•Fe(II) production plays a major role in paddy soil pH increase during submerging.•Great soil pHBC slowed down the decline in paddy soil pH during draining.•Great soil pHBC inhibited Cd mobilization in paddy soils during draining.
The copper transporter (COPT/Ctr) gene family plays a critical part in maintaining the balance of the metal, and many diverse species depend on COPT to move copper (Cu) across the cell membrane. In ...Arabidopsis thaliana, Oryza sativa, Medicago sativa, Zea mays, Populus trichocarpa, Vitis vinifera, and Solanum lycopersicum, a genome-wide study of the COPT protein family was performed. To understand the major roles of the COPT gene family in Kandelia obovata (Ko), a genome-wide study identified four COPT genes in the Kandelia obovata genome for the first time. The domain and 3D structural variation, phylogenetic tree, chromosomal distributions, gene structure, motif analysis, subcellular localization, cis-regulatory elements, synteny and duplication analysis, and expression profiles in leaves and Cu were all investigated in this research. Structural and sequence investigations show that most KoCOPTs have three transmembrane domains (TMDs). According to phylogenetic research, these KoCOPTs might be divided into two subgroups, just like Populus trichocarpa. KoCOPT gene segmental duplications and positive selection pressure were discovered by universal analysis. According to gene structure and motif analysis, most KoCOPT genes showed consistent exon–intron and motif organization within the same group. In addition, we found five hormones and four stress- and seven light-responsive cis-elements in the KoCOPTs promoters. The expression studies revealed that all four genes changed their expression levels in response to copper (CuCl2) treatments. In summary, our study offers a thorough overview of the Kandelia obovata COPT gene family’s expression pattern and functional diversity, making it easier to characterize each KoCOPT gene’s function in the future.
Copper-containing amine oxidases (
) are known to have significant involvement in the process of polyamine catabolism, as well as serving crucial functions in plant development and response to ...abiotic stress. A genome-wide investigation of the CuAO protein family was previously carried out in sweet orange (
) and sweet cherry (
L.). Six
(
) genes were discovered for the first time in the
(Ko) genome through a genome-wide analysis conducted to better understand the key roles of the
gene family in
. This study encompassed an investigation into various aspects of gene analysis, including gene characterization and identification, subcellular localization, chromosomal distributions, phylogenetic tree analysis, gene structure analysis, motif analysis, duplication analysis, cis-regulatory element identification, domain and 3D structural variation analysis, as well as expression profiling in leaves under five different treatments of copper (CuCl
). Phylogenetic analysis suggests that these
, like sweet cherry, may be subdivided into three subgroups. Examining the chromosomal location revealed an unequal distribution of the
genes across four out of the 18 chromosomes in
. Six
genes have coding regions with 106 and 159 amino acids and exons with 4 and 12 amino acids. Additionally, we discovered that the 2.5 kb upstream promoter region of the
predicted many cis elements linked to phytohormones and stress responses. According to the expression investigations, CuCl
treatments caused up- and downregulation of all six genes. In conclusion, our work provides a comprehensive overview of the expression pattern and functional variety of the
gene family, which will facilitate future functional characterization of each
gene.
Purpose
The purpose of this study is to summarize the research progresses in the effects of the interactions between active soil organic carbon (SOC) components and minerals on the sorption, ...immobilization, remobilization, transport, and bioavailability of heavy metals (HMs) in the environment.
Materials and methods
This paper presents a discussion based on a bibliometric analysis of the interactions between SOC components and minerals and their influence on the fate of HMs. An in-depth and comprehensive analysis of publication characteristics of 3351 articles using VOSviewer, Histcite, and Bibliometrix was conducted.
Results and discussion
The analyses revealed that the number of articles in this field varied in four stages and China dominated research in this field. The Chinese Academy of Sciences was the center with the most productive cooperation network and registered the largest number of publications. The analysis of the co-occurrence of keywords showed that the coexistence of SOC components would increase or decrease the adsorption and immobilization of HMs on minerals, and this was influenced by environmental parameters such as pH, redox potential, and solution ionic strength. Anionic HMs have become a research hotspot in recent years, and their environmental behaviors, especially redox reactions at the mineral micro solid-phase interfaces, were significantly influenced by the coexistence of active SOC components. The ternary interaction mechanisms between SOC components, minerals, and HMs were complex and presented no clear reasons why some SOC components would inhibit HM adsorption. Based on the bibliometric analysis and mechanistic insights, we make the following recommendations: Research on the molecular interaction mechanisms at the micro/nanoscale interfaces between SOC components, especially microorganisms and biochar, and minerals with HMs needs to be expanded; the redox transformation of anionic HMs at the organo-mineral interfaces is important for their remediation; the establishment of an accurate model is critical to predict and control the environmental risks of HMs, thus expanding research in this field at the micro/nanoscale could speed up the development of new remediation technologies. There is, therefore, a need to develop more advanced in situ methods for characterizing micro/nanoscale interfaces of ternary systems and the environmental behaviors of HMs at the interfaces.
Conclusions
The environmental behaviors of HMs were affected by the mineral-SOC/soil organic matter (SOM) interaction and environmental conditions. The biochar/microbial-mineral interaction should be of more concern and exploring mineral-SOC/SOM-HM ternary interaction mechanisms by high-resolution characterization technology is necessary.
This study reports the mitigating strategy against salinity by exploring the potential effects of biochar (5%), Arbuscular mycorrhizal fungi (20 g/pot, AMF), and biochar + AMF on maize (Zea mays L.) ...plants grown under saline stress in a greenhouse. The maize was grown on alkaline soil and subjected to four different saline levels; 0, 50, 100, and 150 mM NaCl. After 90 d for 100 mM NaCl treatment, the plant’s height and fresh weight were reduced by 17.84% and 39.28%, respectively, compared to the control. When the saline-treated soil (100 mM NaCl) was amended with AMF, biochar, and biochar + AMF, the growth parameters were increased by 22.04%, 26.97%, 30.92% (height) and 24.79%, 62.36%, and 107.7% (fresh weight), respectively. Compared to the control and single AMF/biochar treatments, the combined application of biochar and AMF showed the most significant effect in improving maize growth under saline stress. The superior mitigating effect of biochar + AMF was attributed to its effective ability in (i) improving soil nutrient content, (ii) enhancing plant nutrient uptake, (iii) increasing the activities of antioxidant enzymes, and (iv improving the contents of palmitoleic acid (C16:1), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). Thus, our study shows that amending alkaline and saline soils with a combination of biochar-AMF can effectively mitigate abiotic stress and improve plant growth. Therefore, it can serve as a reference for managing salinity stress in agricultural soils.
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•The binding of Ca, Cd, Cu, Mn, Ni, and Al with EPS was driven by entropy change.•The metal cations were adsorbed by EPS mainly through specific mechanism.•Fe sorption decreased the ...structural disorder of EPS.•Metal cation sorption made negative charge of EPS less negative.•Metal cation sorption enhanced aggregation of EPS through changed surface charge.
Extracellular polymeric substances (EPS) contain a vast number of functional groups which can provide sorption sites for heavy metal cations in solution, however, the mechanisms for the interaction of EPS with various metal cations were not well understood. In this study, the sorption potential of EPS from Pseudomonas fluorescens for different cations was investigated. The changes of electrokinetic properties that occurred on the surface of EPS once they adsorbed these cations were also studied using zeta potential measurements as a function of pH and cation concentration. The adsorption data fitted Freundlich isotherm better than Langmuir and D–R isotherms. The interactions of the cations with EPS were favourable with the separation factor Kr < 1. Under different pH conditions, the zeta potential of EPS in the different cation solution followed the order: Fe(III) (at pH ≤ 5.0) > Al(III) > Cu(II) > Mn(II) > Ni(II)≈Cd(II) > Ca(II) > EPS, while with respect to the initial cation concentration, the zeta potential of EPS was in the order: Fe(III) > Al(III) > Cu(II) > Cd(II) > Ni(II)≈Mn(II)≈Ca(II). The effect of cation sorption on the surface charge of EPS increased with pH as well as cation concentration. The thermodynamic analysis demonstrated that besides the sorption of Fe which was exothermic, all the other cations were adsorbed through an endothermic process. The ΔSads revealed that most of the cations interacted with EPS through the formation of inner-sphere complexes. The ATR-FTIR analyses confirmed that complexation occurred between the cations and functional groups on the surface of EPS. The zeta potential of EPS shifted to positive value direction due to sorption of cations on EPS, indicating that the specific interactions were involved in the sorption process. This study enhances our understanding of EPS aggregation and heavy metal bio-sorption through the electrokinetic mechanism. The results will provide useful references for immobilization of heavy metals and alleviation of Al toxicity in acidic soils.
Copper (Cu) is a necessary mineral nutrient for plant growth and development and is involved in several morphological, physiological, and biochemical processes; however, high concentrations of Cu can ...negatively impact these processes. The role of stomata in responding to various biotic and abiotic stimuli has not been studied in Bruguiera gymnorhiza, particularly in terms of their coordinated interactions at the molecular, physiological, and biochemical levels. Moreover, numerous plants employ strategies such as the presence of thick waxy cuticles on their leaf epidermis and the closing of stomata to reduce water loss. Thus, this study investigates the accumulation of Cu in B. gymnorhiza and its effect on leaf morphology and the molecular response under different Cu treatments (0, 200, and 400 mg L⁻¹, Cu0, Cu200, and Cu400, respectively) during a two years stress period. The results show that Cu stress affected accumulation and transport, increased the activities of peroxidase and ascorbate peroxidase, concentrations of soluble sugar, proline, and H2O2, and decreased the activity of catalase and content of malondialdehyde. Also, Cu-induced stress decreased the uptake of phosphorus and nitrogen and inhibited plant photosynthesis, which consequently led to reduced plant growth. Scanning electron microscopy combined with gas chromatography-mass spectrometry showed that B. gymnorhiza leaves had higher wax crystals and compositions under increased Cu stress, which forced the leaf’s stomata to be closed. Also, the contents of alkanes, alcohols, primary alcohol levels (C26:0, C28:0, C30:0, and C32:0), n-Alkanes (C29 and C30), and other wax loads were significantly higher, while fatty acid (C12, C16, and C18) was lower in Cu200 and Cu400 compared to Cu0. Furthermore, the transcriptomic analyses revealed 1240 (771 up- and 469 downregulated), 1000 (723 up- and 277 down-regulated), and 1476 (808 up- and 668 downregulated) differentially expressed genes in Cu0 vs Cu200, Cu0 vs Cu400, and Cu200 vs Cu400, respectively. RNA-seq analyses showed that Cu mainly affected eight pathways, including photosynthesis, cutin, suberin, and wax biosynthesis. This study provides a reference for understanding mangrove response to heavy metal stress and developing novel management practices.
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•Copper stress interferes with physiological, biochemical, and transcriptomic processes.•Copper stress promotes wax crystals and composition on the leaf of Bruguiera gymnorhiza.•Copper stress increased wax crystal formation, which directly influenced leaf stomatal size.•Copper stress affects various molecular pathways.
The dual role of biochar for inhibiting soil acidification induced by nitrification was determined through two-step incubation experiments in this study. Ca(OH)2 or biochar was added respectively to ...adjust soil pH to the same values (pH 5.15 and 5.85), and then the amended soils were incubated in the presence of urea for 70 days. The results showed that compared with Ca(OH)2 treatment, both rice straw biochar and peanut straw biochar inhibited the decrease in soil pH and the increase in exchangeable acidity during the incubation. The application of biochars suppressed soil nitrification during the incubation, and thus reduced 7.5 mmol kg−1 and 1.4 mmol kg−1 protons released from nitrification compared to Ca(OH)2 treatments. Compared with Ca(OH)2 treatment, the ammonia-oxidizing bacteria population size was decreased by 8% and 12% in rice straw biochar and peanut straw biochar treatments respectively, which was the main responsibility for the inhibited nitrification after biochar application. In addition, the application of rice straw biochar and peanut straw biochar increased soil pH buffering capacity (pHBC) respectively by 22% and 32%. The increased pHBC played the main role (75%) in inhibiting the acidification of the soil amended with peanut straw biochar, while the rice straw biochar inhibited soil acidification mainly through suppressing nitrification during the incubation. Overall, compared with lime application, biochars can inhibit soil acidification caused by urea application through suppressing the nitrification process and improving the resistance of soils to acidification. The crop residue biochars presented a longer-lasting effect on ameliorating acidic soils than mineral lime.
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•Biochar played a dual role in inhibiting soil acidification from nitrification.•Biochar decreased proton release through suppressing soil nitrification.•Biochar increased soil pH buffering capacity and the resistance to acidification.•Biochar would be a better option to ameliorate acidic soils than liming.
Mangroves are of important economic and environmental value and research suggests that their carbon sequestration and climate change mitigation potential is significantly larger than other forests. ...However, increasing salinity and heavy metal pollution significantly affect mangrove ecosystem function and productivity. This study investigates the tolerance mechanisms of rhizobacteria in the rhizosphere of Avicennia marina under salinity and copper (Cu) stress during a 4-y stress period. The results exhibited significant differences in antioxidant levels, transcripts, and secondary metabolites. Under salt stress, the differentially expressed metabolites consisted of 30% organic acids, 26.78% nucleotides, 16.67% organic heterocyclic compounds, and 10% organic oxides as opposed to 27.27% organic acids, 24.24% nucleotides, 15.15% organic heterocyclic compounds, and 12.12% phenyl propane and polyketides under Cu stress. This resulted in differential regulation of metabolic pathways, with phenylpropanoid biosynthesis being unique to Cu stress and alanine/aspartate/glutamate metabolism and α-linolenic acid metabolism being unique to salt stress. The regulation of metabolic pathways enhanced antioxidant defenses, nutrient recycling, accumulation of osmoprotectants, stability of plasma membrane, and chelation of Cu, thereby improving the stress tolerance of rhizobacteria and A. marina. Even though the abundance and community structure of rhizobacteria were significantly changed, all the samples were dominated by Proteobacteria, Chloroflexi, Actinobacteriota, and Firmicutes. Since the response mechanisms were unbalanced between treatments, this led to differential growth trends for A. marina. Our study provides valuable inside on variations in diversity and composition of bacterial community structure from mangrove rhizosphere subjected to long-term salt and Cu stress. It also clarifies rhizobacterial adaptive mechanisms to these stresses and how they are important for mitigating abiotic stress and promoting plant growth. Therefore, this study can serve as a reference for future research aimed at developing long-term management practices for mangrove forests.
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•Salt-copper (Cu) stress decreased bacterial abundance but increased diversity.•Low and high salt stress significantly increased bacterial abundance.•High salt stress significantly downregulated the content of free amino acids in the rhizosphere.•High Cu and salt-Cu stress promoted N reduction function but inhibited C metabolism.•Phenylpropanoid biosynthesis was unique to copper stress.
Biochar research has experienced a significant increase in the recent two decades. It is growing quickly, with hundreds of reviews, including meta-analyses, that have been published reporting diverse ...effects of biochar on soil properties and plant performance. However, an in-depth synthesis of biochar–soil interactions at the molecular level is not available. For instance, in many meta-analyses, the effects of biochar on soil properties and functions were summarized without focusing on the specificity of the biochar and soil properties. When applied to soils, biochar interacts with different soil components including minerals, organic matter, gases, liquids, and nutrients, while it also changes soil microbial community structure and their occurrence. These different interactions modify soil physicochemical properties with consequences for dynamic changes in nutrient availability and, thus, plant performance. This review systematically analyzed biochar effects on soil properties and functions: (a) soil physical properties; (b) chemical properties; (c) biological properties; and (d) functions (plant performance, nutrient cycling, etc.). Our synthesis revealed that the surface properties of biochar (specific surface area and charge) and its associated nutrient content determine its role in the soil. At the same time, the extent of changes depends on soil properties, suggesting that both biochar and soil properties need to be considered for harvesting benefits of biochar application. Altogether, we believe our synthesis will provide a guide for researchers and practitioners for future research as well as large-scale field applications.
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