Analysis of microbial community composition and diversity in the rhizosphere of Salvia miltiorrhiza at different growth stages.

Salvia miltiorrhiza is a kind of medicinal plant with various pharmacological activities. Few studies on the composition and diversity of rhizosphere microbial communities at different growth stages have been conducted on Salvia miltiorrhiz; in particular, salviorrhiza grows in soil that has been continuously planted for 3 years. The purpose of this study was to understand the changes of soil physicochemical properties of Salvia miltiorrhiza at different growth stages, and to study the composition and diversity of rhizosphere microbial community at different growth stages. Illumina NovaSeq sequencing technology was used to analyze the bacterial 16S rRNA gene and the fungal ITS region in the rhizosphere soil of Salvia miltiorrhiza at different growth stages. The results showed that the dominant bacterial phyla in the Salvia miltiorrhiza rhizosphere were Proteobacteria, Bacteroidetes, Acidobacteria, Firmicutes, Actinobacteria, and Chloroflexi. The dominant fungal phyla were Ascomycota, Mortierellomycota, Basidiomycota, and Rozellomycota. During the growth of Salvia miltiorrhiza, the physical and chemical properties of soil changed. As the Salvia miltiorrhiza grew, the content of available phosphorus, available potassium, pH, nitrate nitrogen, and ammonium nitrogen significantly decreased. Ammonium nitrogen and nitrate nitrogen had a greater impact on the bacterial community structure in the rhizosphere than on the fungal community structure. The work was to reveal differences in the rhizosphere bacterial and fungal community structure during different growth stages of Salvia miltiorrhiza, further understand the changes of rhizosphere microbial ecological characteristics and soil physicochemical properties during the cultivation of Salvia miltiorrhiza.

Antifungal mechanism of rose, mustard, and their blended essential oils against Cladosporium allicinum isolated from Xinjiang naan and its storage application.

AIMS: To reveal the inhibition mechanism of rose, mustard, and blended essential oils against Cladosporium allicinum isolated from Xinjiang naan, and investigate the effect of the three essential oils on oxidative damage and energy metabolism. METHODS AND RESULTS: Rose and mustard essential oils significantly inhibited mycelial growth and spore viability in a dose-dependent relationship. After essential oil treatment, the cell membrane permeability was altered, and significant leakage of intracellular proteins and nucleic acids occurred. SEM observations further confirmed the disruption of cell structure. ROS, MDA, and SOD measurements indicated that essential oil treatment induced a redox imbalance in C. allicinum, leading to cell death. As for energy metabolism, essential oil treatment significantly reduced Na+K+-ATPase, Ca2+Mg2+-ATPase, MDH activity, and CA content, impairing metabolic functions. Finally, storage experiments showed that all three essential oils ensured better preservation of naan, with mustard essential oil having the best antifungal effect. CONCLUSIONS: Rose and mustard essential oils and their blends can inhibit C. allicinum at multiple targets and pathways, destroying cell morphological structure and disrupting metabolic processes.

Analysis on Foodborne Pathogen Contamination of Food Samples in Longnan City from 2013 to 2022.

The objective was to determine the prevalence of foodborne pathogens in food in Longnan City, Gansu Province, China. In this research, we conducted tests on baked foods, catering foods, meat, and fruits and vegetables sold in supermarkets, farmers' markets, restaurants, retail stores, street stalls, and school canteens from 2013 to 2022. We analyzed the variety of foodborne pathogens (Salmonella, Staphylococcus aureus, Listeria monocytogenes, Bacillus cereus, and diarrheagenic Escherichia coli) in different sites and food types. Once foodborne pathogens were detected in the sample, it was deemed unqualified. The total detection rates of foodborne pathogens were 1.559%, 3.349%, 1.980%, 1.040%, 3.383%, and 1.303% in food from supermarkets, farmers' markets, restaurants, retail stores, street stalls, and school canteens, respectively. No pathogenic bacteria were detected in baked foods. Salmonella, S. aureus, L. monocytogenes, B. cereus, and diarrheagenic E. coli were detected in catering foods, among which B. cereus had the highest detection rate. Salmonella was the most common pathogenic bacteria detected in meat, while the detection rate of pathogenic bacteria in fruits and vegetables was low, with only one positive sample for diarrheagenic E. coli. Among the six sites, street stalls (3.382%) and farmers' markets (3.349%) had higher detection rates of pathogens. In general, the detection rate of pathogens from 2013 to 2022 was not high, but there were also some hidden dangers. Catering food is vulnerable to pathogen contamination, and street stalls and farmers' markets are the main sites of pollution. According to the above findings, the regulatory authorities should continue to strengthen supervision, guarantee food safety through early warning, and reduce the risk of food contamination.

An analytical overview of the composition and characteristics of China's food safety standards.

This paper discusses the framework of China's food safety standards and provides a brief overview of the problems and developmental characteristics of food safety in China. The composition and characteristics of China's food safety standards are revealed by an analysis of the changes in China's general food standards, an overview of the characteristics of the hygiene requirements in the production and operation process, and an introduction to food product and test method standards. In conclusion, Chinese food safety standards are still being improved, but they must also be effectively implemented and followed up in real time in order to continuously improve the quality of food and reduce food safety incidents. © 2024 Society of Chemical Industry.

Gas chromatography-ion mobility spectrometry (GC-IMS) technique and its recent applications in grain research.

Grains are the primary source of food for most people worldwide and constitute a major source of carbohydrates. Many novel technologies are being employed to ensure the safety and reliability of grain supply and production. Gas chromatography-ion mobility spectrometry (GC-IMS) can effectively separate and sensitively detect volatile organic compounds. It possesses advantages such as speed, convenience, high sensitivity, no pretreatment, and wide applicability. In recent years, many studies have shown that the application of GC-IMS technology for grain flavor analysis can play a crucial role in grains. This article elucidates the working principle of GC-IMS technology, reviews the application of GC-IMS in grains in the past 5 years. GC-IMS technology is mainly applied in four aspects in grains. In grain classification, it distinguishes varieties, quality, origin, production year, and processing methods based on the trace differences in volatile organic compounds, thereby fulfilling various grain classification requirements such as origin tracing, geographical indication product recognition, variety identification, production year identification, and detection of counterfeit and inferior grain samples. In optimizing the processing technology of grains and their products, it can improve food flavor, reduce undesirable flavors, and identify better processing parameters. In grain storage, it can determine the storage time, detect spoilage phenomena such as mold and discoloration during storage, eliminate pests affecting storage, and predict the vitality of seeds after storage. In aroma evaluation of grains and their processed products, it can assess the impact of new raw materials, new technologies, fermentation processes, and even oral processing on the quality of grain products. This article also summarizes the characteristics of GC-IMS technology, compiles typical grain flavor compounds, and provides prospects for the future application of GC-IMS. © 2024 Society of Chemical Industry.

Application of methyl jasmonate to control chilling tolerance of postharvest fruit and vegetables: a meta-analysis and eliciting metabolism review.

Chilling injury is one of the most significant limitations for low temperature storage of postharvest fruits and vegetables, causing quality deterioration and economic loss. Increasing studies indicated that methyl jasmonate (MeJA) is critical in regulating the postharvest fruit and vegetables chilling tolerance. Based on a meta-analysis, the review analyzed the action of exogenous MeJA application on the chilling index in postharvest fruit and vegetables and summarized MeJA's mechanisms for controlling postharvest chilling injury. The meta-analysis found that MeJA treatment remarkably inhibited postharvest fruit and vegetable chilling injury. Moreover, we concluded the following function mechanism of MeJA on postharvest fruit and vegetable chilling tolerance: (1) Enhancing membrane integrity and energy supply, (2) Increasing antioxidant activity, (3) Enhancing arginine pathway, (4) Enhancing sugar metabolism, (5) Regulating phenolic metabolism, (6) Activating CBF pathway, (7) Regulating HSP accumulation and expression, and (8) Crosstalk with phytohormone. Finally, we summarized the regulatory mechanisms of MeJA on postharvest fruit and vegetable biological processes at the transcriptional and post-translational levels.

Effects of different seasons on bacterial community structure in rose rhizosphere soil.

TO explore the changes of rhizosphere soil bacterial community of Rosa rugosa "Fenghua", Rosa rugosa cv. Plena and Rosa rugosa "Zizhi" in different seasons, the Illumina Miseq sequencing and the correlation network analysis of dominant flora was used. The results showed that the bacterial communities were mainly composed of Proteobacteria, Acidobacteria, Bacteroidetes, and Actinobacteria, with Sphingomonas, GP6, GP4, Novosphingobium, Wps-1_genera_incertae_sedis, and Massilia as the dominant genera. The correlation network analysis showed that, as the dominant group with the highest relative abundance, Sphingomonas had a significant positive correlation with Gemmatimonas, Aridibacter, GP3, GP4, and Flavisolibacter, and a significant negative correlation with Solirubrobacter, indicating that it could work synergistically with a variety of microorganisms to contribute to soil metabolism and the growth and development of roses. The results revealed the diversity of microbial structures in the rhizosphere soil of Rosa rugosa "Fenghua", Rosa rugosa cv. Plena and Rosa rugosa "Zizhi", and this will provide a theoretical basis for exploring the change rules of microbial communities, screening and utilizing beneficial microorganisms, and maintaining the growth and development of roses. KEY POINTS: • Variations from season to season significantly affected the bacterial community structure. • There was less variability in the bacterial community structure between rose varieties. • Sphingomonas was the dominant bacterium in all seasons.

Nanoscale zerovalent iron, carbon nanotubes and biochar facilitated the phytoremediation of cadmium contaminated sediments by changing cadmium fractions, sediments properties and bacterial community structure.

Environment functional materials have been widely used, but whether their effects on the contaminated environment could facilitate phytoremediation is not yet well understood. In this study, starch stabilized nanoscale zerovalent iron (SN), multiwall carbon nanotubes (MW) and tea waste derived biochar (TB) were used to facilitate the phytoremediation of cadmium (Cd) contaminated sediments by Boehmeria nivea (L.) Gaudich. Results showed that 100 mg/kg SN, 500 mg/kg MW and 500 mg/kg TB facilitated phytoremediation, as evidenced by increasing Cd accumulation and/or promoting plant growth. These concentrations of materials increased the reducible fraction of Cd by 9-10% and decreased the oxidizable proportion of Cd by 48-52%, indicating the improvement of Cd bioavailability through converting the oxidizable Cd into reducible form. The activities of urease, phosphatase and catalase, which related to nutrient utilization and oxidative stress alleviation, increased by 20-24%, 25-26%, and 8-9% in the sediments treated with 500 mg/kg MW and 500 mg/kg TB, respectively. In addition, the 16S rRNA gene sequence results showed that these concentrations of materials changed the bacterial diversity. The abundance of Acidobacteria, Actinobacteria, Nitrospirae and Firmicutes were increased by some of the applied materials, which could promote plant growth, change Cd bioavailability and reduce Cd toxicity. These findings indicated that the applied environment functional materials could facilitate the phytoremediation of Cd contaminated environment by changing Cd fractions, sediments properties and bacterial community structure.

Molecular identification and phylogenetic analysis of fungal pathogens isolated from diseased fish in Xinjiang, China.

The outbreaks of fungal diseases in cultured fish have been severe in recent years, which is harmful to the healthy and sustainable development of fish farming. In this study, an investigation was conducted for significant fungal infections of 12 species of fish in four regions in Xinjiang, China, to understand the distribution of local fish fungal pathogens. Twenty-six fungal strains with pathogenicity were isolated, and the challenge experiment showed that eight strains from Changji area had high infection rate to fish eggs. Based on internal transcribed spacer sequence data and molecular analysis, the 26 strains were classified into nine different species of six fungal genera. Phylogenetic analysis showed that all strains were divided into two clades, namely Cluster 1 (contains only the genus Mucor) and Cluster 2 (consists of five small branches), and the distribution of strains from the same region was scattered in two clusters. There is no strict host selectivity for these fungi to infect fish. Mucor sp. are the main fungal pathogen of fish in these four regions, whereas Hypophthalmichthys molitrix and Carassius auratus are two types of fish that were susceptible to pathogen. In addition, the environmental adaptability experiments showed that eight highly pathogenic strains have different adaptability to the environment, and their optimum temperature and pH were 25°C and 7.0, respectively, whereas the concentration of NaCl was negatively correlated with the growth of strains. Therefore, these results indicated that the coinfection of multiple fungal pathogens in a culture region should be considered in the future study.

Adsorption of 17ß-estradiol from aqueous solution by raw and direct/pre/post-KOH treated lotus seedpod biochar.

Five biochars derived from lotus seedpod (LSP) were applied to examine and compare the adsorption capacity of 17ß-estradiol (E2) from aqueous solution. The effect of KOH activation and the order of activation steps on material properties were discussed. The effect of contact time, initial concentration, pH, ionic strength and humic acid on E2 adsorption were investigated in a batch adsorption process. Experimental results demonstrated that the pseudo second-order model fitted the experimental data best and that adsorption equilibrium was reached within 20 hr. The efficiency of E2 removal increased with increasing E2 concentration and decreased with the increase of ionic strength. E2 adsorption on LSP-derived biochar (BCs) was influenced little by humic acid, and slightly affected by the solution pH when its value ranged from 4.0 to 9.0, but considerably affected at pH 10.0. Low environmental temperature is favorable for E2 adsorption. Chemisorption, π-π interactions, monolayer adsorption and electrostatic interaction are the possible adsorption mechanisms. Comparative studies indicated that KOH activation and the order of activation steps had significant impacts on the material. Post-treated biochar exhibited better adsorption capacity for E2 than direct treated, pre-treated, and raw LSP biochar. Pyrolyzed biochar at higher temperature improved E2 removal. The excellent performance of BCs in removing E2 suggested that BCs have potential in E2 treatment and that the biochar directly treated by KOH would be a good choice for the treatment of E2 in aqueous solution, with its advantages of good efficiency and simple technology.

N- and O-Doped Carbon Dots for Rapid and High-Throughput Dual Detection of Trace Amounts of Iron in Water and Organic Phases.

In this work, we report a dual use of highly fluorescent N- and O-doped carbon dots (CDs) for rapid and high-throughput trace analysis of iron in water and organic phases. The CDs are rapidly synthesized in a sealed vessel via microwave irradiation within 5 min, and they exhibit high quantum yields of 80% with sensitive quenching responses to iron contents. Combined with a microplate fluorescence reader, a rapid and high-throughput assay for ions is further developed. The whole process from the CD synthesis to the detection output can be accomplished within 15 min. The limits of detection for Fe3+ in aqueous solution and ferrocene in organic gasoline are determined down to 0.05 mM. Furthermore, this method has been successfully used to determine the level of irons in real gasoline for quality evaluation. The results have an excellent agreement with atomic absorption spectrophotometric measurements. The CD-based facile assay with lower cost, use of less sample, and higher-throughput holds great promise as a powerful tool for iron detection in water and organic phase samples.

Removal of 17ß-Estradiol from water by adsorption onto montmorillonite-carbon hybrids derived from pyrolysis carbonization of carboxymethyl cellulose.

In this work, we demonstrated the preparation of the carbonized montmorillonite/carboxymethyl cellulose (MMT/CMC) hybrids and their application as an adsorbent for efficient removal of 17ß-Estradiol (ßE2). X-ray diffractometer (XRD) results showed that CMC intercalation reached saturation at a CMC to MMT weight ratio of 1; transmission electron microscope (TEM) measurements clearly revealed that carbonization caused graphenes distribute on the MMT surfaces; pyrolysis temperature at 600 °C yielded novel MMT/CMC sample of high surface areas as reflected by Brunauer-Emmett-Teller (BET) surface area. The adsorbed amount of ßE2 under various conditions decreased in the order MMT/CMC1:1(600) > MMT/CMC1:1(450) > MMT/CMC1:1(300) ∼ MMT/CMC2:1(600) ∼ MMT > MMT/CMC5:1(600). The removal of ßE2 by MMT/CMC1:1(600) occurred very quickly, and the adsorption kinetics could be well fitted by the Ritchie nth-order kinetic model; the best-fit adsorption isotherm model was Freundlich model. The MMT/CMC1:1(600) also exhibited good regeneration performance after five adsorption/desorption cycles. The experimental results also showed that the adsorption of ßE2 on the MMT/CMC1:1(600) composite could contribute to hydrophobic partitioning, π-π staking interaction, H-bond interaction, pore-filling effect and simple van der Waals interaction. This highly effective and novel adsorbent can be easily synthesized and regenerated, indicating its great potential in drinking and wastewater purification for endocrine disruptor compounds.

Remediation of contaminated soils by biotechnology with nanomaterials: bio-behavior, applications, and perspectives.

Soil contamination caused by heavy metals and organic pollutants has drawn world-wide concern. Biotechnology has been applied for many years to the decontamination of soils polluted with organic and inorganic contaminants, and novel nanomaterials (NMs) has attracted much concern due to their high capacity for the removal/stabilization/degradation of pollutants. Recently, developing advanced biotechnology with NMs for the remediation of contaminated soils has become a hot research topic. Some researchers found that bioremediation efficiency of contaminated soils was enhanced by the addition of NMs, while others demonstrated that the toxicity of NMs to the organism negatively influenced the repair capacity of polluted soils. This paper reviews the application of biotechnology and NMs in soil remediation, and further provides a critical view of the effects of NMs on the phytoremediation and micro-remediation of contaminated soils. This review also discusses the future research needs for the combined application of biotechnology and NMs in soil remediation.

Simultaneous removal of hexavalent chromium and o-dichlorobenzene by isolated Serratia marcescens ZD-9.

Heavy metals-organics mixture pollution is increasingly concerned and simultaneous removal of organic pollutants and heavy metals is becoming significant. In this study, a strain was isolated from the sediment of a tannery effluent outfalls, which can remove o-dichlorobenzene (o-DCB) and Cr(VI) simultaneously. The bacterial isolate was identified as Serratia marcescens by the 16S rRNA gene sequences. The strain removed about 90% of o-DCB and more than 80% of Cr(VI) at the concentration of 1.29 g L-1 o-DCB and 20 mg L-1 Cr(VI). In the presence of concomitant pollutant o-DCB, the optimal pH (8.0) and temperature (30 °C) were determined for Cr(VI) removal. Changes of the bacterial cells and intracellular black Cr(III) sediments were observed by the TEM auxiliary analysis. The results of the FTIR spectroscopy analysis indicated that hydroxyl, amide and polysaccharides were involved in the process of Cr(VI) removal.

Alginate-modified biochar derived from Ca(II)-impregnated biomass: Excellent anti-interference ability for Pb(II) removal.

A novel biochar modified with sodium alginate was prepared using Ca(II)-impregnated biomass, and used to remove metals from aqueous solutions. The maximum adsorption capacity for Pb(II) was estimated to be 1.225 mmol/g (253.6 mg/g), which is far more than that of most adsorbents. Moreover, the modified biochar had a great anti-interference ability for effective removal of Pb(II) from multi-metal system. The biochar still had strong ability to adsorb Pb(II) when the initial concentrations of interfering ions were 5 times higher than that of Pb(II). Functional groups and minerals of the biochar worked for Pb(II) removal and the anti-interference ability. On the one hand, carboxyl could complex with Pb(II) through monodentate and bidentate bridging; on the other hand, Pb(II) was easier to form a precipitate with minerals than other metals. This study suggested that the novel biochar had the potential for practical application in effective removal of Pb(II) from wastewater.

Nanoscale zero-valent iron assisted phytoremediation of Pb in sediment: Impacts on metal accumulation and antioxidative system of Lolium perenne.

Lead (Pb) is a highly toxic environmental pollutant, and could result in toxic effects on living organisms. The effects of 0, 100, 200, 500, 1000 and 2000 mg/kg of nZVI on plant growth, Pb accumulation and antioxidative responses of Lolium perenne were investigated. Results showed that the total Pb contents in L. perenne with the treatment of low concentrations of nZVI (100, 200 and 500 mg/kg) were higher than those in the non-nZVI treatments, and the highest Pb accumulation capacity of 1175.40 µg per pot was observed in L. perenne with the treatment of 100 mg/kg nZVI. However, the total Pb contents in L. perenne decreased at high concentrations of nZVI (1000 and 2000 mg/kg). This might be resulted from the decrease of photosynthetic chlorophyll content and the aggravated oxidative stress induced by the high concentration of nZVI, which caused the decrease of plant biomass and metal accumulation capacity in plant. Moreover, the sequential extraction experiments results showed that the lowest acid soluble fraction of Pb in the sediments was found in the treatment with 100 mg/kg of nZVI, indicating that 100 mg/kg was the optimum concentration for nZVI to assist the phytoremediation of Pb-polluted sediment. To conclude, these findings provide a promising method to remediate Pb-polluted sediment by nZVI assisted phytoremediation.

The bioenergetics mechanisms and applications of sulfate-reducing bacteria in remediation of pollutants in drainage: A review.

Sulfate-reducing bacteria (SRB), a group of anaerobic prokaryotes, can use sulfur species as a terminal electron acceptor for the oxidation of organic compounds. They not only have significant ecological functions, but also play an important role in bioremediation of contaminated sites. Although numerous studies on metabolism and applications of SRB have been conducted, they still remain incompletely understood and even controversial. Fully understanding the metabolism of SRB paves the way for allowing the microorganisms to provide more beneficial services in bioremediation. Here we review progress in bioenergetics mechanisms and application of SRB including: (1) electron acceptors and donors for SRB; (2) pathway for sulfate reduction; (3) electron transfer in sulfate reduction; (4) application of SRB for economical and concomitant treatment of heavy metal, organic contaminants and sulfates. Moreover, current knowledge gaps and further research needs are identified.

Heavy metal leachability in soil amended with zeolite- or biochar-modified contaminated sediment.

In this work, reuse probability of heavy metal-contaminated sediment for land application was discussed using a 100-day column leaching assessment under the situation of simulated acid rain. For comparison, NaCl-modified zeolite and biochar were firstly studied for their adsorption capacity for Cu, Cd, and Pb in aqueous solution, and then their stabilizing effects on the three metals in sediment-soil mixture. Characteristic results indicated that NaCl-modified zeolite had properties more conducive to metal adsorption than biochar, including higher BET surface area and more negative surface charges. Adsorption capacities of NaCl-modified zeolite fitted by Langmuir isotherm model were 24.83, 35.57, and 133.16 mg g-1 for Cu, Cd, and Pb, respectively. Leaching results demonstrated that metal concentrations in the leachates of soil receiving zeolite- or biochar-modified sediment reduced significantly after 100 days compared with that of soil receiving bare sediment. Moreover, the NaCl-modified zeolite presented a better performance in stabilizing the three metals than biochar from the BCR sequential extraction result. Therefore, stabilization of the dredged contaminated sediment by modified zeolite ensures an environmentally friendly reuse of the sediment on land and makes the sediment treatment operation-able and cost-effective.

Influence of sodium dodecyl sulfate coating on adsorption of methylene blue by biochar from aqueous solution.

Biochar is regarded as a promising new class of materials due to its multifunctional character and the possibility of effectively coupling different properties. With increasing introduction into the environment, environmental chemicals such as surfactants will load onto the released biochar and change its physicochemical characteristics and adsorption behavior toward pollutants. In this study, sodium dodecyl sulfate (SDS), as one type of anionic surfactant, was coated onto biochar with different loading amounts. The influence of SDS loading onto biochar's physicochemical properties were investigated by Fourier transform infrared (FT-IR) spectroscopy, elemental analysis, zeta potential and Brunauer-Emmett-Teller (BET) surface area and pore size distribution analysis. Results showed that the pore size of the biochar decreased gradually with the increase of SDS loading because of the surface-adsorption and pore-blocking processes; the pH of the point of zero charge (pHPZC) decreased with increasing SDS loading. Although surface-coating with SDS decreased the pore size of the biochar, its adsorption capacity toward Methylene Blue (MB) significantly increased. The biochar-bound SDS introduced functional groups and negative charges to the biochar surface, which could thus enhance the adsorption of MB via hydrogen bonding and electrostatic interaction. The results can shed light on the underlying mechanism of the influence of anionic surfactants on the adsorption of MB by biochar.

Effects of calcium at toxic concentrations of cadmium in plants.

MAIN CONCLUSION: This review provides new insight that calcium plays important roles in plant growth, heavy metal accumulation and translocation, photosynthesis, oxidative damage and signal transduction under cadmium stress. Increasing heavy metal pollution problems have raised word-wide concerns. Cadmium (Cd), being a highly toxic metal, poses potential risks both to ecosystems and human health. Compared with conventional technologies, phytoremediation, being cost-efficient, highly stable and environment-friendly, is believed to be a promising green technology for Cd decontamination. However, Cd can be easily taken up by plants and may cause severe phytotoxicity to plants, thus limiting the efficiency of phytoremediation. Various researches are being done to investigate the effects of exogenous substances on the mitigation of Cd toxicity to plants. Calcium (Ca) is an essential plant macronutrient that involved in various plant physiological processes, such as plant growth and development, cell division, cytoplasmic streaming, photosynthesis and intracellular signaling transduction. Due to the chemical similarity between Ca and Cd, Ca may mediate Cd-induced physiological or metabolic changes in plants. Recent studies have shown that Ca could be used as an exogenous substance to protect plants against Cd stress by the alleviation of growth inhibition, regulation of metal uptake and translocation, improvement of photosynthesis, mitigation of oxidative damages and the control of signal transduction in the plants. The effects of Ca on toxic concentrations of Cd in plants are reviewed. This review also provides new insight that plants with enhanced Ca level have improved resistance to Cd stress.