Comprehensive Analysis of Elemental and Metabolite Composition in Boraginaceae Species From Türkiye

Boraginaceae plants, including four endemic species from Türkiye, were analyzed for organic and inorganic compositions using inductively coupled plasma mass spectrometry (ICP-MS) and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) to explore their nutritional, medicinal, and ecological significance. This study examined 18 species, identifying key elements, such as sodium (87 600.359-118 049.272 g/kg), potassium (98 876.885-145 587.899 g/kg), and iron (70 396.436-116 416.076 g/kg), which showed significant variation. Metabolite profiling revealed the presence of alkaloids, flavonoids, and tannins in most samples. Additionally, 42 amino acids and 35 phenolic compounds were detected, with rosmarinic acid and proline being particularly abundant. Rosmarinic acid was most concentrated in Oi and Ml samples, whereas proline levels ranged from 3023.8086 to 7693.8549 nmol/mL. The study highlights the intricate metabolic and elemental profiles of Boraginaceae species, shedding light on their ecological adaptations and therapeutic potentials. Spearman correlation analysis suggested significant relationships among phenolic compounds, amino acids, and elemental compositions, indicating potential applications in nutrition, pharmacology, and biodiversity conservation.

Integrating QTL mapping and GWAS to decipher the genetic mechanisms behind the calcium contents of Brassica napus shoots

Brassica napus is an important oil crop worldwide, and its shoots are rich in vitamin C, calcium, and selenium. Functional oilseed-vegetable-dual-purpose varieties can increase the subsidiary value of B. napus. Consumption of high-calcium B. napus shoots can effectively help provide essential elements to the human body. To investigate the genetic mechanisms underlying the calcium concentrations of B. napus shoots, quantitative trait loci (QTL) mapping, using a population of 189 recombinant inbred lines, and a genome-wide association study, using an association panel of 202 diverse accessions, were performed. A total of 12 QTLs controlling calcium content were identified using the recombinant inbred line population in five environments. Among them, qCaC.22GY-A05-1 was considered the major QTL, with a phenotypic variation of 10.10%. In addition, 228 single nucleotide polymorphisms significantly related to calcium content were identified using the genome-wide association study in six environments, and they were distributed on all of the chromosomes, except A10. Finally, 10 candidate genes involved in regulating calcium absorption and transport in B. napus shoots were identified. However, no overlapping intervals were found through a comprehensive analysis of the two datasets. These results provide valuable information for understanding the genetic control of calcium concentration in B. napus shoots.

Starvation from within: How heavy metals compete with essential nutrients, disrupt metabolism, and impair plant growth

Nutrient starvation is a critical consequence of heavy metal toxicity, severely impacting plant health and productivity. This issue arises from various sources, including industrial activities, mining, agricultural practices, and natural processes, leading to the accumulation of metals such as aluminum (Al), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), mercury (Hg), and nickel (Ni) in soil and water. Heavy metal exposure disrupts key physiological processes, particularly nutrient uptake and transport, resulting in nutrient imbalances within the plant. Essential nutrients are often unavailable or improperly absorbed due to metal chelation and interference with transporter functions, exacerbating nutrient deficiencies. This nutrient starvation, coupled with oxidative stress induced by heavy metals, manifests in impaired photosynthesis, stunted growth, and reduced crop yields. This review presents important insights into the molecular mechanisms driving nutrient deprivation in plants exposed to heavy metals, emphasizing the roles of transporters, transcription factors, and signaling pathways. It also examines the physiological and biochemical effects, such as chlorosis, necrosis, and altered metabolic activities. Lastly, we explore strategies to mitigate heavy metal-induced nutrient starvation, including phytoremediation, soil amendments, genetic approaches, and microbial interventions, offering insights for enhancing plant resilience in contaminated soils.

Barriers and carriers for transition metal homeostasis in plants

Transition metals are types of metals with high chemical activity. They play critical roles in plant growth, development, reproduction, and environmental adaptation, as well as in human health. However, the acquisition, transport, and storage of these metals pose specific challenges due to their high reactivity and poor solubility. In addition, distinct yet interconnected apoplastic and symplastic diffusion barriers impede their movement throughout plants. To overcome these obstacles, plants have evolved sophisticated carrier systems to facilitate metal transport, relying on the tight coordination of vesicles, enzymes, metallochaperones, low-molecular-weight metal ligands, and membrane transporters for metals, ligands, and metal-ligand complexes. This review highlights recent advances in the homeostasis of transition metals in plants, focusing on the barriers to transition metal transport and the carriers that facilitate their passage through these barriers.

Cobalt-induced oxidative stress and defense responses of Adhatoda vasica proliferated shoots

BACKGROUND

Levels of heavy metal pollution are increasing due to industrial activities and urban expansion. While cobalt (Co) can be toxic to plants at high levels and isn't considered essential, it plays a beneficial role in many enzymes and is critical for various biological functions. We conducted experiments to determine how Adhatoda vasica proliferated shoots react to exposure to various Co concentrations (50-1000 µM). We employed physiological and biochemical markers to elucidate the response mechanisms of this medicinal plant. The experiment was conducted in two replicates per treatment. The statistical analysis was based on data from four biological replicates per treatment.

RESULTS

Interestingly, the lowest Co concentration (50 µM) increased proliferated shoot growth by 41.45%. In contrast, higher Co concentrations (100-1000 µM) had detrimental effects on proliferated shoot development, water content, and photosynthetic pigment concentrations. As Co concentration increased, proliferated shoots produced excessive concentrations of reactive oxygen species (ROS). This ROS overproduction is believed to be the primary cause of oxidative damage, as evidenced by the elevated concentrations (18.46%-72.84%) of malondialdehyde (MDA) detected. In response to Co stress, non-enzymatic antioxidants were activated in a concentration-dependent manner. Co administration significantly increased the concentrations of different stress-protective compounds in shoots, including total antioxidants (133.18%), ascorbic acids (217.94%), free and bound phenolics (97.70% and 69.72%, respectively), proline (218.59%), free amino acids (206.96%), soluble proteins (65.97%), and soluble carbohydrates (18.52%). FTIR analysis further corroborated changes in the chemical composition of proliferated shoots. The analysis revealed variations in the peaks associated with major macromolecules, including phenolic compounds, lipids, proteins, carbohydrates, cellulose, hemicellulose, and sugars.

CONCLUSIONS

Our study offers the first comprehensive investigation into mechanisms by which Co stress triggers oxidative damage and alters functional groups in the medicinal plant, Adhatoda vasica.

Cupriavidus metallidurans: a species-non-specific and multifaceted plant growth-promoting bacteria

Here we report growth promoting effects of Cupriavidus metallidurans on plants, and provide evidence for the underlying mechanisms of the growth promoting effects. In a series of greenhouse experiments on tomato, maize, and wheat, complemented with genetic analysis of Arabidopsis mutants, we tested the effects of the bacteria on seed germination, root and shoot growth, metal uptake, gas exchange parameters, and stomatal and xylem traits in maize, wheat, and tomato plants. Results showed that the bacteria substantially accelerate seed germination, increase shoot and root biomass, enhance photosynthetic performance, acidify the rhizosphere, increase metal uptake, and modulate stomatal and xylem traits. Analysis of Arabidopsis mutants impaired in auxin or ethylene perception and signaling revealed that the growth promoting effects of the bacteria and accelerating seed germination is independent of auxin and ethylene. We conclude that the bacteria acidify the rhizosphere and thereby increase metal uptake. It increases stomatal density and xylem area leading to increased stomatal conductance and hydraulic conductivity, leading to increased photosynthesis. Altogether, our data suggest C. metallidurans as a plant growth-promoting bacteria with striking abilities to manipulate different plant traits including stomatal density and xylem structure.

Combining Metal(loid) and Secondary Metabolite Levels in Olea europaea L. Samples for Geographical Identification

To fight counterfeits, and to protect the consumer, the interest in certifying the origin of agricultural goods has been growing in recent years. In this context and to increase the accuracy of zoning models, multiple analytical techniques must be combined via a multivariate approach. During the sampling campaign, leaves and fruits (olives or drupes) were collected from multiple orchards and farms. By means of HPLC-DAD, metabolite levels were evaluated and combined with the trace and ultra-trace metal/metalloid levels evaluated by ICP-MS (QqQ). The combined dataset was then used to develop a model for geographical traceability. Furthermore, the mineral content of the soil, evaluated by means of ICP-MS, was correlated with both the mineral content in the leaves and drupes and the metabolomic profiles to further investigate the connection between the orchard's location and characteristics of the final products.

Autecology and determination of relationships between nutrients in soil and sage plant (Salvia eremophila Boiss.) in the south of Yazd province

This study aims to investigate the autecology and determine the relationship between the nutritional elements in the soil and the Sage plant (Salvia eremophila Boiss.) in the south of Yazd province. The main habitats were determined, which contained various ecological characteristics. Total potassium (K), total nitrogen (N), total phosphorus (P), total sugar content (TSC), and proline content of the plants were determined. In addition, macro and microelement contents such as total N, extractable K, extractable magnesium (Mg), available P, available iron (Fe), and available manganese (Mn) of the study areas were determined. The highest concentrations of TSC (72.90 mg kg-1 ± 3.87) and TN (0.265 g kg-1 ± 0.021) of the plant, and also the highest extractable Mg (26.60 mg kg-1 ± 1.70) and available Fe (0.44 mg kg-1 ± 0.19), of soil were related to the Qavam Abad habitat. The highest concentrations of total K (17.495 g kg-1 ± 4.91) and total P (1.206 g kg-1 ± 0.257) of plants, and the highest extractable K (356.68 g kg-1 ± 63.53) of soil belonged to the Tang Chenar Station. The highest TN content (6.3 g kg-1 ± 1.21) of soil and the highest proline content (0.015 g kg-1 ± 0.003) of plants was related to the Damgahan habitat. Also, the concentrations of soil available Mn and available P had the highest levels in the Damgahan (0.60 g kg-1 ± 0.34) and Qavam Abad habitats (0.075 g kg-1 ± 30.74), respectively. There was no significant difference between the amount of nutrients and soil elements in the studied stations (p < 0.05). There was a positive and significant correlation between the amount of soil TN and plant TN (Pvalues = 0.001, R2 = 0.87). An inverse and significant correlation was also observed between the amount of soil available P and plant total P (Pvalues = 0.014, R2 = - 0.72). This study highlights the various environmental controls over soil's physicochemical properties, which have significant implications for the management of soil nutrients.

Plant nutrition challenges for a sustainable agriculture of the future

This article offers a comprehensive review of sustainable plant nutrition concepts, examining a multitude of cutting-edge techniques that are revolutionizing the modern area. The review copes with the crucial role of biostimulants as products that stimulate plant nutrition processes, including their potential for biofertilization, followed by an exploration of the significance of micronutrients in plant health and growth. We then delve into strategies for enhancing plants' tolerance to mineral nutrient contaminants and the promising realm of biofortification to increase the essential nutrients necessary for human health. Furthermore, this work also provides a concise overview of the burgeoning field of nanotechnologies in fertilization, while the integration of circular economy principles underscores the importance of sustainable resource management. Then, with examined the interrelation between micronutrients. We conclude with the future challenges and opportunities that lie ahead in the pursuit of more sustainable and resilient plant systems.

Deciphering Cadmium Accumulation in Peanut Kernels through Growth Stages and Source Organs: A Multi-Stable Isotope Labeling Study

The mechanisms of cadmium (Cd) uptake and redistribution throughout the peanut lifecycle remain unclear. This study employed multi-isotope labeling techniques in hydroponic and soil-foliar systems, revealing that Cd uptake during podding (Cdp) constituted 73.7% of kernel Cd content, whereas contributions from the flowering (Cdf) and seedling (Cds) stages were 22.2 and 4.1%, respectively. Stem-stored Cd (Cdstem) contributes 53.2% to kernel Cd accumulation, while leaf-stored Cd (Cdleaf) contributes 46.8%. Prestored Cdf in shoots demonstrated the most efficient transport to pods, approximately twice that of Cds and Cdp. Cds and Cdf were predominantly stored in leaves (51.0%), while Cdp mainly in stems (46.3%), 2.8 times its presence in leaves (16.5%), indicating distinct root-stem-kernel translocation. In the transfer of shoot Cd from stems to pods, 29.3% of Cdleaf and 25.0% of Cdstem were exported. This study provides novel insights into Cd dynamics in peanuts, establishing a foundation for future Cd regulation strategies.

Arbuscular mycorrhizal fungi on the development and copper content in corn and sorghum plants

The concentration of copper in the soil increased with the intensification of agricultural activities, mainly in grape production areas and orchards as a result of the application of pesticides. Arbuscular mycorrhizal fungi make up the microbial biomass of the soil and appear as an alternative to be researched for the development of plants in an environment contaminated with copper. The purpose of this pot study was to analyze the influence of arbuscular mycorrhizal fungi on the development and content of copper in corn and sorghum plants. Soil treatments were: without inoculum (control) and two arbuscular mycorrhizal (Acaulospora scrobiculata and Rhizoglomus clarum) and five doses of copper (0, 100, 200, 300, and 400 mg Cu kg-1 soil); with seven repetitions. Plant height, stem diameter, number of tillers, root volume, shoot and root dry weight yields, shoot, root and grain Cu concentrations, pseudo-total soil Cu, percentage of mycorrhizal colonization and relative mycorrhizal efficiency index in reducing Cu concentration in root and shoot of corn and sorgum were evaluated. Morphological parameters of sorghum and corn were reduced with at high Cu doses in the soil, and the inoculation with Acaulospora scrobiculata and Rhizoglomus clarum resulted in greater development and lower Cu concentration in the dry mass of the shoot and root parts sorghum and corn plants.

Chitosan mitigated the adverse effect of Cd by regulating antioxidant activities, hormones, and organic acids contents in pepper (Capsicum annum L.)

Chitosan (CTS) is one of the natural healers' alternatives to chemical products within the scope of good agricultural practices. It can be used in the improvement of agriculture (prevention of toxic metal uptake by plants) due to its chelating feature of metal ions. This study aims to investigate the effectiveness of chitosan in eliminating the negative effects of cadmium (Cd) stress on pepper (Capsicum annum L.). The results showed that Cd stress significantly decreased plant growth, chlorophyll content, and leaf water relative content, followed by an increase in proline, antioxidant enzyme activities, and abscisic acid (ABA) content. According to the results, Cd treatment (200 mg kg-1) significantly increased the aspartate, glutamate, asparagine, histidine, and phenylalanine content, while it significantly decreased the content of endogenous hormones such as gibberellic acid (GA), indole-3-acetic acid (IAA), and salicylic acid (SA). However, CTS application decreased the uptake of Cd and caused a decrease in hydrogen peroxide (H2O2), abscisic acid (ABA), and melondialdehyde (MDA) content, as well as an increase in plant performance, and GA, IAA, and SA content in the plants grown under Cd pollution compared to the ones treated with Cd and without CTS. This study suggests that CTS application helps pepper seedlings tolerate Cd stress through a decrease in Cd uptake, and an increase in amino acids and hormone content.

Extensive ICP-MS and HPLC-QQQ detections reveal the content characteristics of main metallic elements and polyphenols in the representative commercial tea on the market

The content of polyphenols and metal elements in tea has an important impact on the choice of consumers. In this study, we conducted a comparative analysis of ten elements including Fe, Mg, Al, Zn, Cu, Mn, Ni, Cr, Pb, and As in 122 representative tea samples from 20 provinces. The results showed that the difference of metal content among six tea categories was greater than that among provinces, and the overall metal content of black tea was relatively higher. The contents of all elements from high to low were: Mg > Mn > Al > Fe > Zn > Cu > Ni > Cr > Pb > As. The contents of Ni, Fe, Al, Zn and Mn showed significant differences among multiple types of tea categories. While the detection rates of Pb and As were 10.7 and 24.6%, respectively. The contents of all elements were in line with the national limit standards. Meanwhile, the relative contents of theanine, caffeine and a total of 53 polyphenolic compounds in 122 tea samples were detected. The analysis showed that the content of these compounds differed least between green and yellow tea, and the largest difference between black tea and oolong tea. This study provides important support for consumers to choose tea rationally.

Food groups consumption and urinary metal mixtures in women from Northern Mexico

OBJECTIVE

We aimed to evaluate the association between food groups and mixtures of urinary metal concentrations in a sample of women; as well as identify the most important metals within each mixture.

METHODS

This is a cross-sectional analysis between food groups consumption and mixtures of various metals in urine from 439 women, ≥18 years old, from Northen Mexico. We estimated the dietary intake of 20 food groups through a validated semi-quantitative food frequency questionnaire. Urinary metal concentration of aluminum, antimony, arsenic, barium, cadmium, cesium, chromium, cobalt, copper, lead, manganese, magnesium, molybdenum, nickel, selenium, thallium, tin, vanadium, and zinc, were measured by inductively coupled plasma triple quad. We used weighted quantile sum (WQS) regression with binomial family specification to assess the association of food groups and metal mixtures, as well as to identify the most important ones.

RESULTS

We identified tin, lead, and antimony as the most important metals, in the metal mixtures that were positively associated with the consumption of eggs, non-starchy vegetables, fruits, seafood, corn, oil seeds, chicken, soda, legumes, red and/or processed meats, as well as negatively with the consumption of alliums, corn tortillas and/or vegetable oils.

CONCLUSION

Our findings suggest that food consumption is related to more than one metal in the study sample, and highlights the presence of some of them. Further research is required to identify the possible sources of metals in food, as well as the chronic adverse health effects attributed to their simultaneous presence.

Regulation of mineral elements in Hordeum brevisubulatum by Epichloë bromicola under Cd stress

In this study, wild barley (Hordeum brevisubulatum) infected (E+) and uninfected (E-) by Epichloë bromicola were used for hydroponic experiments during the seedling stage. Various attributes, such as the effect of fungal endophyte on the growth and development of wild barley, the absorption of cadmium (Cd) and mineral elements (Ca, Mg, Fe, Mn, Cu, Zn), subcellular distribution, and chemical forms were investigated under CdCl2 stress. The results showed that the fungal endophy significantly reduced the Ca content and percentage of plant roots under Cd stress. The Fe and Mn content of roots, the mineral element content of soluble fractions, and the stems in the pectin acid or protein-chelated state increased significantly in response to fungal endophy. Epichloë endophyte helped Cd2+ to enter into plants; and reduced the positive correlation of Ca-Fe and Ca-Mn in roots. In addition, it also decreased the correlation of soluble components Cd-Cu, Cd-Ca, Cd-Mg in roots, and the negative correlation between pectin acid or protein-chelated Cd in stems and mineral elements, to increase the absorbance of host for mineral elements. In conclusion, fungal endophy regulated the concentration and distribution of mineral elements, while storing more Cd2+ to resist the damage caused by Cd stress. The study could provide a ground for revealing the Cd tolerance mechanism of endophytic fungal symbionts.

Physiological and molecular mechanisms of ZnO quantum dots mitigating cadmium stress in Salvia miltiorrhiza

This study delved into the physiological and molecular mechanisms underlying the mitigation of cadmium (Cd) stress in the model medicinal plant Salvia miltiorrhiza through the application of ZnO quantum dots (ZnO QDs, 3.84 nm). A pot experiment was conducted, wherein S. miltiorrhiza was subjected to Cd stress for six weeks with foliar application of 100 mg/L ZnO QDs. Physiological analyses demonstrated that compared to Cd stress alone, ZnO QDs improved biomass, reduced Cd accumulation, increased the content of photosynthetic pigments (chlorophyll and carotenoids), and enhanced the levels of essential nutrient elements (Ca, Mn, and Cu) under Cd stress. Furthermore, ZnO QDs significantly lowered Cd-induced reactive oxygen species (ROS) content, including H2O2, O2-, and MDA, while enhancing the activity of antioxidant enzymes (SOD, POD, APX, and GSH-PX). Additionally, ZnO QDs promoted the biosynthesis of primary and secondary metabolites, such as total protein, soluble sugars, terpenoids, and phenols, thereby mitigating Cd stress in S. miltiorrhiza. At the molecular level, ZnO QDs were found to activate the expression of stress signal transduction-related genes, subsequently regulating the expression of downstream target genes associated with metal transport, cell wall synthesis, and secondary metabolite synthesis via transcription factors. This activation mechanism contributed to enhancing Cd tolerance in S. miltiorrhiza. In summary, these findings shed light on the mechanisms underlying the mitigation of Cd stress by ZnO QDs, offering a potential nanomaterial-based strategy for enhancing Cd tolerance in medicinal plants.

Can nutrients act as signals under abiotic stress?

Plant cells are in constant communication to coordinate development processes and environmental reactions. Under stressful conditions, such communication allows the plant cells to adjust their activities and development. This is due to intercellular signaling events which involve several components. In plant development, cell-to-cell signaling is ensured by mobile signals hormones, hydrogen peroxide (H2O2), nitric oxide (NO), or hydrogen sulfide (H2S), as well as several transcription factors and small RNAs. Mineral nutrients, including macro and microelements, are determinant factors for plant growth and development and are, currently, recognized as potential signal molecules. This review aims to highlight the role of nutrients, particularly calcium, potassium, magnesium, nitrogen, phosphorus, and iron as signaling components with special attention to the mechanism of response against stress conditions.

Metal Interactions in the Ni Hyperaccumulating Population of Noccaea caerulescens Monte Prinzera

Hyperaccumulation is a fascinating trait displayed by a few plant species able to accumulate large amounts of metal ions in above-ground tissues without symptoms of toxicity. Noccaea caerulescens is a recognized model system to study metal hyperaccumulation and hypertolerance. A N. caerulescens population naturally growing on a serpentine soil in the Italian Apennine Mountains, Monte Prinzera, was chosen for the study here reported. Plants were grown hydroponically and treated with different metals, in excess or limiting concentrations. Accumulated metals were quantified in shoots and roots by means of ICP-MS. By real-time PCR analysis, the expression of metal transporters and Fe deficiency-regulated genes was compared in the shoots and roots of treated plants. N. caerulescens Monte Prinzera confirmed its ability to hypertolerate and hyperaccumulate Ni but not Zn. Moreover, excess Ni does not induce Fe deficiency as in Ni-sensitive species and instead competes with Fe translocation rather than its uptake.

The crucial elements for lettuce (Lactuca sativa L.) growth under DMA stress and the linkage with DMA behavior: A new application of ionome

Dimethylarsinic acid (DMA) is one of the common arsenic (As) species present in soil and is more toxic to plants than others. Identifying the crucial elements for plant growth under DMA stress is essential to enhance plant tolerance to DMA. Herein, we provided for the first time an ionome-based approach to address this issue. The phenotype, As species and concentrations of 11 essential elements in lettuce tissues were monitored under exposures of 0.1, 0.5, 1, 2, 5 mg L-1 DMA in hydroponic culture for 32 days. Lettuces remained normal (no significant difference in phenotype from the control) under 0.1-2 mg L-1 DMA stress, and were inhibited with fresh weights of leaf and root under 5 mg L-1 DMA stress. Integrating the difference in ionome profiles between the two growth states (normal and inhibited) and the responses of the individual element, Mg and S were clarified as the most possible candidates for the crucial elements for lettuce growth under DMA stress. Under 5 mg L-1 DMA stress, the accumulation of Mg and S declined, yet their BCF values were significantly increased, which was consistent with the change in BCF of DMA. Based on the physiological functions of Mg and S and the toxicity of DMA, it could be inferred that the enhanced transfer of Mg and S to leaves should be induced by the potential damage caused by the increased DMA accumulation in leaves, and would result in a shortage of both elements in roots as well as the growth inhibition.

Selenium foliar application contributes to decrease ratio of water-soluble fluoride and improve physio-biochemical components in tea leaves

The tea plant accumulates elevated levels of fluoride (F) from environmental sources. Drinking tea containing high F levels poses a potential threat to human health. Selenium (Se) was applied by foliar spray to investigate its effects on F accumulation and physiology in tea plant. Foliar application of different forms of Se, i.e., Na2SeO3, Kappa-selenocarrageenan, Selenomethionine and Nanoselenium, reduced F content in tea leaves by 10.17 %-44.28 %, 16.12 %-35.41 %, 22.19 %-45.99 % and 22.24 %-43.82 %, respectively. Foliar spraying Se could increase F accumulation in pectin through increasing pectin content and pectin demethylesterification to bind more F in the cell wall, which decreased the proportion of water-soluble fluoride in tea leaves. Application of Se significantly decreased the contents of chromium (39.6 %-72.0 %), cadmium (48.3 %-84.4 %), lead (2.2 %-44.4 %) and copper (14.1 %-44.6 %) in tea leaves. Foliar spraying various forms of Se dramatically increased the Se content and was efficiently transformed into organic Se accounting for more than 80 % in tea leaves. All Se compounds increased peroxidase activity by 3.3 %-35.5 % and catalase activity by 2.6 %-99.4 %, reduced malondialdehyde content by 5.6 %-37.1 %, and increased the contents of chlorophyll by 0.65 %-31.8 %, carotenoids by 0.24 %-27.1 %, total catechins by 1.6 %-21.0 %, EGCG by 4.4 %-17.6 % and caffeine by 9.1 %-28.6 %. These results indicated that Se application could be served as a potential efficient and safe strategy diminishing the concentration of F in tea leaves.

The microwave-assisted synthesis of silica nanoparticles and their applications in a soy plant culture

A rapid and environmentally friendly synthesis of thermodynamically stable silica nanoparticles (SiO2-NPs) from heating via microwave irradiation (MW) compared to conductive heating is presented, as well as their evaluations in a soy plant culture. The parameters of time and microwave power were evaluated for the optimization of the heating program. Characterization of the produced nanomaterials was obtained from the dynamic light scattering (DLS) and zeta potential analyses, and the morphology of the SiO2-NPs was obtained by transmission electron microcopy (TEM) images. From the proposed synthesis, stable, monodisperse, and amorphous SiO2-NPs were obtained. Average sizes reported by DLS and TEM techniques were equal to 11.6 nm and 13.8 nm, respectively. The water-stable suspension of SiO2-NPs shows a zeta potential of -31.80 mV, and the homogeneously spheroidal morphology observed by TEM corroborates with the low polydispersity values (0.300). Additionally, the TEM with fast Fourier transform (FFT), demonstrates the amorphous characteristic of the nanoparticles. The MW-based synthesis is 30 times faster, utilizes 4-fold less reagents, and is ca. 18-fold cheaper than conventional synthesis through conductive heating. After the synthesis, the SiO2-NPs were added to the soil used for the cultivation of soybeans, and the homeostasis for Cu, Ni, and Zn was evaluated through the determination of their total contents by inductively coupled plasma mass spectrometry (ICP-MS) in soy leaves and also through bioimages obtained using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Although the results corroborate through both techniques, they also show the influence of these nanoparticles on the elemental distribution of the leaf surface with altered homeostasis of such elements from both transgenic crops compared to the control group.

Reflectance spectroscopy as a promising tool for 'sensing' metals in hyperaccumulator plants

MAIN CONCLUSION

The VNIR reflectance spectra of nickel hyperaccumulator plant leaves have spectral variations due to high nickel concentrations and this property could potentially be used for discovery of these plants.  Hyperaccumulator plants accumulate high concentrations of certain metals, including manganese, cobalt, or nickel. Of these metals, the divalent ions of nickel have three absorption bands in the visible to near-infrared region which may cause variations in the spectral reflectance of nickel hyperaccumulator plant leaves, but this has not been investigated previously. In this shortproof-of-concept study, the spectral reflectance of eight different nickel hyperaccumulator plant species leaves were subjected to visible and near-infrared and shortwave infrared (VNIR-SWIR) reflectance spectrum measurements in dehydrated state, and for one species, it was also assessed in hydrated state. Nickel concentrations in the plant leaves were determined with other methods and then correlated to the spectral reflectance data. Spectral variations centred at 1000 ± 150 nm were observed and had R-values varying from 0.46 to 0.96 with nickel concentrations. The extremely high nickel concentrations in nickel hyperaccumulator leaves reshape their spectral reflectance features, and the electronic transition of nickel-ions directly contributes to absorption at ~ 1000 nm. Given that spectral variations are correlated with nickel concentrations it make VNIR-SWIR reflectance spectrometry a potential promising technique for discovery of hyperaccumulator plants, not only in the laboratory or herbarium, but also in the field using drone-based platforms. This is a preliminary study which we hope will instigate further detailed research on this topic to validate the findings and to explore possible applications.

Agronomic and ionomics indicators of high-yield, mineral-dense, and low-Cd grains of wheat (Triticum aestivum L.) cultivars

The accumulation of toxic and essential nutrient elements in wheat grain influences wheat yield, grain nutritional quality, and human health. Here, we assessed the potential for breeding wheat cultivars to combine high yield with low cadmium and high iron and/or zinc concentrations in grains, and we screened appropriate cultivars. A pot experiment was conducted to explore differences in grain cadmium, iron, and zinc concentrations among 68 wheat cultivars, as well as their relationships with other nutrient elements and agronomic characters. The results showed 2.04-, 1.71-, and 1.64-fold differences in grain cadmium, iron, and zinc concentrations, respectively, among the 68 cultivars. Grain cadmium concentration was positively correlated with grain zinc, iron, magnesium, phosphorus, and manganese concentrations. Grain copper concentration was positively correlated with grain zinc and iron concentrations, but not with grain cadmium concentration. Therefore, copper has a potential role in regulating grain iron and zinc accumulation without influencing cadmium concentration in wheat grain. There were no significant relationships between grain cadmium concentration and four important wheat agronomic characters (i.e., grain yield, straw yield, thousand kernel weight, and plant height), indicating that the breeding of low-cadmium-accumulating cultivars with dwarfism and high yield characteristics is possible. On cluster analysis, four cultivars (Ningmai11, Xumai35, Baomai6, and Aikang58) exhibited low-cadmium and high-yield characteristics. Among them, Aikang58 contained moderate iron and zinc concentrations, while Ningmai11 had relatively high iron but low zinc concentrations in the grain. These results imply that it is feasible to breed high-yield dwarf wheat with low cadmium and moderate iron and zinc concentrations in the grain.

New potential transporter CIPAS8 enhances cadmium hypersensitivity and cobalt tolerance

KEY MESSAGE

CIPAS8 is a novel Cd-influx and Co-efflux transporters, and Ser86 and Cys128 might play a decisive role in Co-binding and translocation. Cadmium (Cd) is among the most toxic heavy metals and is a widespread environmental pollutant. Cobalt (Co) is a mineral nutrient that is essential for plant growth and development, but high concentrations may be toxic. Cadmium-induced protein AS8 (CIPAS8) is widely distributed among plant species and might be induced by heavy metals, but its function has not been studied previously. In this study, Populus euphratica PeCIPAS8 and Salix linearistipularis SlCIPAS8 were investigated. The transcription of both genes was significantly enhanced under Cd and Co stresses. PeCIPAS8 and SlCIPAS8 conferred sensitivity to Cd in transgenic yeast, allowing higher quantities of Cd to accumulate within the cells, whereas SlCIPAS8 also conferred tolerance to Co and reduced Co accumulation. The determinants of substrate selectivity of the SlCIPAS8 protein were examined by site mutagenesis, which indicated that the Ser at 86th (S86) substituted for Arg (R) [S86R] and Cys at 128th (C128) substituted for Ser [C128S] mutations limited the protein's capability for Co translocation. These results suggested that PeCIPAS8 and SlCIPAS8 may be involved in Cd uptake into the plant cell. SlCIPAS8 can reduce excess Co accumulation to maintain intracellular Co homeostasis, and the site mutations S86R and C128S were essential for Co transport. These findings provide insight into the function of CIPAS8 and highlight its potential for utilization in phytoremediation applications.

The role of silver nanoparticles effects in the homeostasis of metals in soybean cultivation through qualitative and quantitative laser ablation bioimaging

BACKGROUND

Nanoparticles (NPs) are currently found in the world in the form of natural colloids and volcanic ash, as well as in anthropogenic sources, such as nanofertilizers; however, in the literature, there is still a lack of toxicological evidence, risk assessment, and regulations about the use and environmental impact of NPs in the agroindustrial system. Therefore, the aim of this work was to evaluate alterations caused by the presence of AgNPs during the development of soybean plants.

METHODS

The BRS232 non-transgenic (NT) soybean plant and 8473RR (T_RR) and INTACTA RR2 PRO (T_Intacta) transgenic soybean plants were irrigated for 18 days under controlled conditions with deionized water (control), AgNPs, and AgNO₃. The isotopes ¹⁰⁷Ag⁺, ⁵⁵Mn⁺, ⁵⁷Fe⁺, ⁶³Cu⁺, and ⁶⁴Zn⁺ were mapped in leaves, using ¹³C⁺ as an internal standard (IS), and carried out using a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technique with a Nd:YAG (213 nm) laser source in the imagagin mode using the LA-iMageS software and also Mathlab.

RESULTS

Leaf images showed a low Ag translocation, indicated by the basal signal of this ion. Additionally, the presence of Ag in the ionic form and as NPs altered the homeostasis of ¹¹²Cd⁺, ⁶⁴Zn⁺, ⁵⁵Mn⁺, ⁶³Cu⁺, and ⁵⁷Fe⁺ in different ways. Quantitative image analysis was performed for Cu.

CONCLUSION

The behavior of T_RR and T_Intacta plants was different in the presence of ionic silver or AgNPs, confirming that the metabolism of these two plants, despite both being transgenic, are different. Through the images, it was observed that the response of plants was different in the face of the same stress conditions during their development.

Geographic isolation and environmental heterogeneity contribute to genetic differentiation in Cephalotaxus oliveri

Evaluating the contributions of geographic distance and environmental heterogeneity to the genetic divergence can inform the demographic history and responses to environmental change of natural populations. The isolation-by-distance (IBD) reveals that genetic differentiation among populations increases with geographic distance, while the isolation-by-environment (IBE) assumes a linear relationship between genetic variation and environmental differences among populations. Here, we sampled and genotyped 330 individuals from 18 natural populations of Cephalotaxus oliveri throughout the species' distribution. Twenty-eight EST-SSR markers were applied to analyze population genetics, for the investigation of the driving factors that shaped spatial structure. In addition, we identified the outlier loci under positive selection and tested their association with environmental factors. The results showed a moderate genetic diversity in C. oliveri and high genetic differentiation among populations. Population structure analyses indicated that 18 populations were clustered into two major groups. We observed that the genetic diversity of central populations decreased and the genetic differentiation increased towards the marginal populations. Additionally, the signatures of IBD and IBE were detected in C. oliveri, and IBE provided a better contribution to genetic differentiation. Six outlier loci under positive selection were demonstrated to be closely correlated with environmental variables, among which bio8 was associated with the greatest number of loci. Genetic evidence suggests the consistency of the central-marginal hypothesis (CMH) for C. oliveri. Furthermore, our results suggest that temperature-related variables played an important role in shaping genetic differentiation.

An eco-sustainable approach towards heavy metals remediation by mangroves from the coastal environment: A critical review

Mangroves provide various ecosystem services, carbon sequestration, biodiversity depository, and livelihoods. They are most abundant in marine and coastal ecosystems and are threatened by toxic contaminants like heavy metals released from various anthropogenic activities. However, they have significant potential to survive in salt-driven environments and accumulate various pollutants. The adverse effects of heavy metals have been extensively studied and recognized as toxic to mangrove species. This study sheds light on the dynamics of heavy metal levels, their absorption, accumulation and transport in the soil environment in a mangrove ecosystem. The article also focuses on the potential of mangrove species to remove heavy metals from marine and coastal environments. This review concludes that mangroves are potential candidates to clean up contaminated water, soil, and sediments through their phytoremediation ability. The accumulation of toxic heavy metals by mangroves is mainly through roots with limited upward translocation. Therefore, promoting the maintenance of biodiversity and stability in the coastal environment is recommended as an environmentally friendly and potentially cost-effective approach.

Nano-biofertilizers as bio-emerging strategies for sustainable agriculture development: Potentiality and their limitations

Nanotechnology is a burgeoning revolutionary technology in the 21st century. Climate emergencies caused by natural or anthropogenic activities have tragically consequential repercussions on agricultural output worldwide. Modern cropping systems profoundly rely on synthetic fertilizers to deliver necessary nutrients, yet their prolonged and persistent administration is hazardous to the environment, soil fertility, and nutritional dynamics of the rhizospheric microbiome. By addressing the drawback of physico-chemically synthesized nano-dimensioned fertilizer, this review emphasizes on integrating nanoparticles and biofertilizers conjointly as nano-biofertilizers (NBF) which can safeguard global food security, in light of the population surge. Inoculation with nanoparticles and biofertilizers strengthens plant growth and stress tolerance. However, combined together (NBF), they have emerged as a more economically and environmentally sustainable, highly versatile, and long-lasting agriculture tool. Microbe-based green synthesis using the encapsulation of inorganic nanoparticles of Si, Zn, Cu, Fe, Ni, Ti, and Ag as well as organic materials, including chitosan, cellulose, and starch, to formulate NBFs can eliminate the constraints of conventional fertilizer contamination. The application of NBFs is in its infancy in agriculture, yet it has promising potential for transforming traditional farming techniques into smart agriculture, compared to any of the existing strategies. From this perspective, this review is an attempt to provide a comprehensive understanding of the formulations, fabrication, and characterization of NBFs while unraveling the underlying mechanisms of plant-NBF interactions along with their contribution to climate change-induced biotic and abiotic stress tolerance. We substantially summarize the latest advancements of field applications of NBFs for precision farming. Moreover, we critically revised their applications in agro-ecosystems according to the current literature, while also discussing the bottlenecks and future trends for developing potent NBFs.

Environmental implication of MoS2 nanosheets: Effects on maize plant growth and soil microorganisms

Molybdenum disulfide (MoS₂) nanosheets have been used extensively in a variety of fields including medical and industrial. However, little is known about their toxicity effects, especially to edible plants. In this greenhouse study, maize (Zea mays) seedlings were exposed for 4 weeks, through the soil route, to 10 and 100 mg/kg of 2H MoS₂ nanosheets. Plant growth, physiological parameters (chlorophyll, antioxidants, and MDA), along with Mo and nutrient element contents were determined in plant tissues. Results showed that at both doses, the nanosheets decreased plant growth. Inductively coupled plasma-mass spectrometry data also showed that both 2H MoS₂ concentrations allowed Mo absorption and translocation by maize plants. Additionally, at 100 mg/kg the nanosheets significantly reduced Ca, Mg, Mn, and Zn in leaves, and Na in roots. Gene sequencing data of 16S rRNA showed, that MoS₂ nanosheets changed the soil microbial community structure, compared with the untreated control. In addition, nitrogen-fixing microorganisms such as Burkholderiales, Rhizobiales and Xanthobacteraceae were enriched. Overall, the data suggest that, even at low dose (10 mg/kg), the 2H MoS₂ nanosheets perturbed both the nutrient uptake by maize plants and the soil microbial communities.

Study of the mineral contents of Matricaria pubescens and Brocchia cinerea from Algeria

Two species of plants commonly used for mainly their therapeutic values and available in some herbalists shops, namely: Brocchia cinerea and Matricaria pubescens that both belong to asteraceae family, and encountered mainly in the Algerian desert, have drawn attention in the scope of assessing their mineral contents, in fact minerals play an important role in the plant homeostasis and metabolism, on the other hand they may influence the health conditions mainly due to toxicity, and also the benefits that the plant consumer could have, the current study aimed to assess the contents of Al, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Zn, As, Na, K, Mg, P, S and SI, beside comparing the obtained results to other similar studies, the aerial parts of the plants are collected from several sites then mineralized and analyzed using ICP-AES and AAS, high levels of Na, K and Mg have been noted, on the other hands levels of metals were noted to be overall marginal, except for Al and Hg for the sample of Brocchia cinerea from El oued, the levels of As also seemed to be high in all the samples, inversely to the levels of S and P which seemed lower than those noted for other plants in paralleled studies, while that similar results were found for Zn, Fe, the chemical and geologic features of the soils may be the influencing factor. Additionally the current study may put first milestone for the establishment of national guidelines regarding the mineral contents of medicinal plants.

Nutrient reallocation between stem and leaf drives grazed grassland degradation in inner Mongolia, China

BACKGROUND

Decline in height and aboveground biomass of the plant community are critical indicators of grassland ecosystem degradation. Nutrient reallocation induced by grazing occurs among different organs, which balances the trade-off between growth and defense. However, it is not yet clear how nutrient reallocation strategies affect plant community structure and functions in grazed grasslands. A grazing experiment was conducted in a typical steppe in Inner Mongolia, China. We investigated plant community characteristics and measured plant functional traits of dominant species (Leymus chinensis and Cleistogenes squarrosa) at individual and population levels. Carbon (C), nitrogen (N), phosphorus (P), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn) concentrations of stem and leaf in the two species were also determined.

RESULTS

N, P, Cu, Fe, Mn, and Zn concentrations in leaves and stems of L. chinensis and C. squarrosa significantly increased with grazing intensity, and microelements (Cu, Fe, Mn, and Zn) were more sensitive to grazing. The nutrient slopes of macro- and microelements in leaves were significantly higher than those in stems under grazing, indicating that nutrient resources were preferentially allocated to leaves and enhanced the compensatory growth of leaves in the grazed grassland. With increasing grazing intensity, the aboveground biomass of stems and leaves in the two species significantly decreased, but leaf to stem ratio increased at the individual level, indicating that plants preferentially allocated biomass to leaves under grazing. The increase in leaf to stem ratio due to nutrient reallocation between the two organs significantly reduced height and aboveground biomass at population and community levels, driving grassland ecosystem degradation.

CONCLUSION

Our study revealed the driving forces of community structure and function degradation in grazed grasslands from the perspective of nutrient resource allocation, and provided insights into plant adaptation strategies to grazing.

Continuous Systems Bioremediation of Wastewaters Loaded with Heavy Metals Using Microorganisms

Heavy metal pollution is a serious concern of the modern era due to its widespread negative effects on human health and to the environment. Conventional technologies applied for the uptake of this category of persistent pollutants are complex, often expensive, and inefficient at low metal concentrations. In the last few years, non-conventional alternatives have been studied in search of better solutions in terms of costs and sustainability. Microbial adsorbents are one of the biomass-based sorbents that have extensively demonstrated excellent heavy metals removal capacity even at low concentrations. However, most of the carried-out research regarding their application in wastewater treatment has been performed in discontinuous systems. The use of microorganisms for the uptake of metal ions in continuous systems could be an important step for the upscale of the remediation processes since it facilitates a faster remediation of higher quantities of wastewaters loaded with heavy metals, in comparison with batch systems removal. Thus, the current research aims to analyze the available studies focusing on the removal of metal ions from wastewaters using microorganisms, in continuous systems, with a focus on obtained performances, optimized experimental conditions, and the sustainability of the bioremoval process. The present work found that microbial-based remediation processes have demonstrated very good performances in continuous systems. Further sustainability analyses are required in order to apply the bioremediation technology in an optimized environmentally friendly way in large-scale facilities.

Drought specifically downregulates mineral nutrition: Plant ionomic content and associated gene expression

One of the main limiting factors of plant yield is drought, and while the physiological responses to this environmental stress have been broadly described, research addressing its impact on mineral nutrition is scarce. Brassica napus and Triticum aestivum were subjected to moderate or severe water deficit, and their responses to drought were assessed by functional ionomic analysis, and derived calculation of the net uptake of 20 nutrients. While the uptake of most mineral nutrients decreased, Fe, Zn, Mn, and Mo uptake were impacted earlier and at a larger scale than most physiological parameters assessed (growth, ABA concentration, gas exchanges and photosynthetic activity). Additionally, in B. napus, the patterns of 183 differentially expressed genes in leaves related to the ionome (known ionomic genes, KIGs) or assumed to be involved in transport of a given nutrient were analyzed. This revealed three patterns of gene expression under drought consisting of up (transport of Cl and Co), down (transport of N, P, B, Mo, and Ni), or mixed levels (transport of S, Mg, K, Zn, Fe, Cu, or Mn) of regulation. The three patterns of gene regulations are discussed in relation to specific gene functions, changes of leaf ionomic composition and with consideration of the crosstalks that have been established between elements. It is suggested that the observed reduction in Fe uptake occurred via a specific response to drought, leading indirectly to reduced uptake of Zn and Mn, and these may be taken up by common transporters encoded by genes that were downregulated.

Plant Nutrition: An Effective Way to Alleviate Abiotic Stress in Agricultural Crops

By the year 2050, the world's population is predicted to have grown to around 9-10 billion people. The food demand in many countries continues to increase with population growth. Various abiotic stresses such as temperature, soil salinity and moisture all have an impact on plant growth and development at all levels of plant growth, including the overall plant, tissue cell, and even sub-cellular level. These abiotic stresses directly harm plants by causing protein denaturation and aggregation as well as increased fluidity of membrane lipids. In addition to direct effects, indirect damage also includes protein synthesis inhibition, protein breakdown, and membranous loss in chloroplasts and mitochondria. Abiotic stress during the reproductive stage results in flower drop, pollen sterility, pollen tube deformation, ovule abortion, and reduced yield. Plant nutrition is one of the most effective ways of reducing abiotic stress in agricultural crops. In this paper, we have discussed the effectiveness of different nutrients for alleviating abiotic stress. The roles of primary nutrients (nitrogen, phosphorous and potassium), secondary nutrients (calcium, magnesium and sulphur), micronutrients (zinc, boron, iron and copper), and beneficial nutrients (cobalt, selenium and silicon) in alleviating abiotic stress in crop plants are discussed.

Biochemical Analysis and Toxicity Assessment of Utilization of Argon Oxygen Decarbonization Slag as a Mineral Fertilizer for Tall Fescue (Festuca arundinacea Schreb) Planting

Argon oxygen decarbonization (AOD) slag refers to a byproduct of stainless steel (SS) production, which has caused considerable environmental stress. Finding an effective approach for recycling AOD slag is essential to environmental safety. In this work, batch leaching tests were carried out to explore the leaching behavior of AOD slag and soil. Pot experiments was conducted to analyze the fertilization effect of AOD slag for tall fescue (Festuca arundinacea Schreb) planting. The plant height, biomass, total root length (TRL), root surface area (RSA), root tips (RT), root hairs (RH)), chlorophyll content, malondialdehyde (MDA) content, and antioxidant enzyme activities of the tall fescue seedlings were measured. As indicated from the results, adding AOD slag into soil increased soil pH. The leaching concentration of Ca, Si, Al, Cr of the AOD slag was higher than the original soil, while that of Mg, Mn, and Fe was lower. Low addition rate (≤1%) of AOD slag fertilization was good for plant height, biomass, root growth, and chlorophyll synthesis, whereas high addition rate (≥2%) exerted an opposite effect. Elevating the rate of AOD slag fertilization increased the Cr accumulation in the tall fescue seedling that aggravated damage of reactive oxygen species (ROS). When the AOD slag fertilization was at a low rate (≤1%), ROS scavenging was attributed to the synergistic effects of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) defense systems, while at a high rate (≥2%) of AOD slag fertilization, scavenging of excessive ROS could be mainly due to the CAT defense system.

Effect of CeO2 nanoparticles on plant growth and soil microcosm in a soil-plant interactive system

The impact of CeO₂ nanoparticles (NPs) on plant physiology and soil microcosm and the underlying mechanism remains unclear to date. This study investigates the effect of CeO₂ NPs on plant growth and soil microbial communities in both the rhizosphere of cucumber seedlings and the surrounding bulk soil, with CeCl₃ as a comparison to identify the contribution of the particulate and ionic form to the phytotoxicity of CeO₂ NPs. The results show that Ce was significantly accumulated in the cucumber tissue after CeO₂ NPs exposure. In the roots, 5.3% of the accumulated Ce has transformed to Ce³⁺. This transformation might take place prior to uptake by the roots since 2.5% of CeO₂ NPs was found transformed in the rhizosphere soil. However, the transformation of CeO₂ NPs in the bulk soil was negligible, indicating the critical role of rhizosphere chemistry in the transformation. CeO₂ NPs treatment induced oxidative stress in the roots, but the biomass of the roots was significantly increased, although the Vitamin C (Vc) content and soluble sugar content were decreased and mineral nutrient contents were altered. The soil enzymatic activity and the microbial community in both rhizosphere and bulk soil samples were altered, with rhizosphere soil showing more prominent changes. CeCl₃ treatment induced similar effects although less than CeO₂ NPs, suggesting that Ce³⁺ released from CeO₂ NPs contributed to the CeO₂ NPs induced impacts on soil health and plant physiology.

Phytotoxicity and Accumulation of Copper-Based Nanoparticles in Brassica under Cadmium Stress

The widespread use of copper-based nanoparticles expands the possibility that they enter the soil combined with heavy metals, having a toxic effect and posing a threat to the safety of vegetables. In this study, single and combined treatments of 2 mg/L Cd, 20 mg/L Cu NPs and 20 mg/L CuO NPs were added into Hoagland nutrient solution by hydroponics experiments. The experimental results show that copper-based Nanoparticles (NPs) can increase the photosynthetic rate of plants and increase the biomass of Brassica. Cu NPs treatment increased the Superoxide Dismutase (SOD), Peroxidase (POD) and catalase (CAT) activities of Brassica, and both NPs inhibited ascorbate peroxidase (APX) activity. We observed that Cd + Cu NPs exhibited antagonistic effects on Cd accumulation, inhibiting it by 12.6% in leaf and 38.6% in root, while Cd + CuO NPs increased Cd uptake by 73.1% in leaves and 22.5% in roots of Brassica. The Cu content in the shoots was significantly negatively correlated with Cd uptake. The Cd content of each component in plant subcellular is soluble component > cytoplasm > cell wall. Cu NPs + Cd inhibited the uptake of Zn, Ca, Fe, Mg, K and Mn elements, while CuO NPs + Cd promoted the uptake of Mn and Na elements. The results show that copper-based nanoparticles can increase the oxidative damage of plants under cadmium stress and reduce the nutritional value of plants.

Soil and foliar exposure of soybean (Glycine max) to Cu: Nanoparticle coating-dependent plant responses

In this study, we investigated the effects of citric acid (CA) coated copper oxide nanoparticles (CuO NPs) and their application method (foliar or soil exposure) on the growth and physiology of soybean (Glycine max). After nanomaterials exposure via foliar or soil application, Cu concentration was elevated in the roots, leaves, stem, pod, and seeds; distribution varied by plant organ and surface coating. Foliar application of CuO NPs at 300 mg/L and CuO-CA NPs at 75 mg/L increased soybean yield by 169.5% and 170.1%, respectively. In contrast, foliar and soil exposure to ionic Cu with all treatments (75 and 300 mg/L) had no impact on yield. Additionally, CuO-CA NPs at 300 mg/L significantly decreased Cu concentration in seeds by 46.7%, compared to control, and by 44.7%, compared to equivalent concentration of CuO NPs. Based on the total Cu concentration, CuO NPs appeared to be more accessible for plant uptake, compared to CuO-CA NPs, inducing a decrease in protein content by 56.3% and inhibiting plant height by 27.9% at 300 mg/kg under soil exposure. The translocation of Cu from leaf to root and from the root to leaf through the xylem was imaged by two-photon microscopy. The findings indicate that citric acid coating reduced CuO NPs toxicity in soybean, demonstrating that surface modification may change the toxic properties of NPs. This research provides direct evidence for the positive effects of CuO-CA NPs on soybean, including accumulation and in planta transfer of the particles, and provides important information when assessing the risk and the benefits of NP use in food safety and security.

A copper switch for inducing CRISPR/Cas9-based transcriptional activation tightly regulates gene expression in Nicotiana benthamiana

BACKGROUND

CRISPR-based programmable transcriptional activators (PTAs) are used in plants for rewiring gene networks. Better tuning of their activity in a time and dose-dependent manner should allow precise control of gene expression. Here, we report the optimization of a Copper Inducible system called CI-switch for conditional gene activation in Nicotiana benthamiana. In the presence of copper, the copper-responsive factor CUP2 undergoes a conformational change and binds a DNA motif named copper-binding site (CBS).

RESULTS

In this study, we tested several activation domains fused to CUP2 and found that the non-viral Gal4 domain results in strong activation of a reporter gene equipped with a minimal promoter, offering advantages over previous designs. To connect copper regulation with downstream programmable elements, several copper-dependent configurations of the strong dCasEV2.1 PTA were assayed, aiming at maximizing activation range, while minimizing undesired background expression. The best configuration involved a dual copper regulation of the two protein components of the PTA, namely dCas9:EDLL and MS2:VPR, and a constitutive RNA pol III-driven expression of the third component, a guide RNA with anchoring sites for the MS2 RNA-binding domain. With these optimizations, the CI/dCasEV2.1 system resulted in copper-dependent activation rates of 2,600-fold and 245-fold for the endogenous N. benthamiana DFR and PAL2 genes, respectively, with negligible expression in the absence of the trigger.

CONCLUSIONS

The tight regulation of copper over CI/dCasEV2.1 makes this system ideal for the conditional production of plant-derived metabolites and recombinant proteins in the field.

Impact of nanoparticles and their ionic counterparts derived from heavy metals on the physiology of food crops

Heavy metals and their engineered nanoparticle (NP) counterparts are emerging contaminants in the environment that have captured the attention of researchers worldwide. Although copper, iron, zinc and manganese are essential micronutrients for food crops, higher concentrations provoke several physiological and biochemical alterations that in extreme cases can lead to plant death. The effects of heavy metals on plants have been studied but the influence of nanoparticles (NPs) derived from these heavy metals, and their comparative effect is less known. In this critical review, we have found similar impacts for copper and manganese ionic and NP counterparts; in contrast, iron and zinc NPs seem less toxic for food crops. Although these nutrients are metals that can be dissociated in water, few authors have conducted joint ionic state and NP assays to evaluate their comparative effect. More efforts are thus required to fully understand the impact of NPs and their ion counterparts at the physiological, metabolic and molecular dimensions in crop plants.

Fertilizer Efficiency and Risk Assessment of the Utilization of AOD Slag as a Mineral Fertilizer for Alfalfa (Medicago sativa L.) and Perennial Ryegrass (Lolium perenne L.) Planting

Argon oxygen decarburization (AOD) slag is the by-product of the stainless steel refining process, which has caused considerable environmental stress. In this work, the utilization of AOD slag as mineral fertilizer for alfalfa (Medicago sativa L.) and perennial ryegrass (Lolium perenne L.) planting were investigated by pot experiments. The morpho-physiological parameters of biomass, plant height, root morphology and the biochemical parameters of malondialdehyde (MDA) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, peroxidase (POD) activity, and chlorophyll were measured. The accumulation of chromium in plants was also determined for an environmental safety perspective. It was found that low rates (≤0.5 wt.% for alfalfa and ≤2 wt.% for perennial ryegrass) of AOD slag fertilization are beneficial to the growth of these two plants. However, the soil enrichment with higher AOD slag amounts resulted in the reduction of biomass, plant height, and root growth. Compared with the alfalfa, the perennial ryegrass showed higher tolerance for AOD slag fertilization. The toxicity of the utilization of AOD slag as mineral fertilizer for perennial ryegrass planting is slight. Health risks induced by the consumption of the alfalfa grown on the soil with high AOD slag rates (≥8 wt.%) were detected.

Excess Zinc Supply Reduces Cadmium Uptake and Mitigates Cadmium Toxicity Effects on Chloroplast Structure, Oxidative Stress, and Photosystem II Photochemical Efficiency in Salvia sclarea Plants

Salvia sclarea L. is a Cd2+ tolerant medicinal herb with antifungal and antimicrobial properties cultivated for its pharmacological properties. However, accumulation of high Cd2+ content in its tissues increases the adverse health effects of Cd2+ in humans. Therefore, there is a serious demand to lower human Cd2+ intake. The purpose of our study was to evaluate the mitigative role of excess Zn2+ supply to Cd2+ uptake/translocation and toxicity in clary sage. Salvia plants were treated with excess Cd2+ (100 μM CdSO4) alone, and in combination with Zn2+ (900 μM ZnSO4), in modified Hoagland nutrient solution. The results demonstrate that S. sclarea plants exposed to Cd2+ toxicity accumulated a significant amount of Cd2+ in their tissues, with higher concentrations in roots than in leaves. Cadmium exposure enhanced total Zn2+ uptake but also decreased its translocation to leaves. The accumulated Cd2+ led to a substantial decrease in photosystem II (PSII) photochemistry and disrupted the chloroplast ultrastructure, which coincided with an increased lipid peroxidation. Zinc application decreased Cd2+ uptake and translocation to leaves, while it mitigated oxidative stress, restoring chloroplast ultrastructure. Excess Zn2+ ameliorated the adverse effects of Cd2+ on PSII photochemistry, increasing the fraction of energy used for photochemistry (ΦPSII) and restoring PSII redox state and maximum PSII efficiency (Fv/Fm), while decreasing excess excitation energy at PSII (EXC). We conclude that excess Zn2+ application eliminated the adverse effects of Cd2+ toxicity, reducing Cd2+ uptake and translocation and restoring chloroplast ultrastructure and PSII photochemical efficiency. Thus, excess Zn2+ application can be used as an important method for low Cd2+-accumulating crops, limiting Cd2+ entry into the food chain.

Evaluation of the Mineral Content in Forage Palm (Opuntia ficus-indica Mill and Nopalea cochenillifera) Using Chemometric Tools

An acid digestion procedure of the forage palm (Opuntia ficus-indica Mill and Nopalea cochenilifera) employing a closed digestor block applied full 2⁴ factorial design was optimized. The optimal conditions were HNO₃ 5.0 mol L^-1, 2.0 mL of H₂O₂ 30% m m^-1, 120 min of digestion, and heating temperature of 180 °C. The certified reference materials of apple leaves (NIST 1515) and tomato leaves (Agro C1003a) were used to evaluate the accuracy of the analytical method. The concentrations of the macroelements were (in % m m^-1) Ca (1.32-3.71), K (0.88-5.29), Mg (0.70-1.78), and P (0.03-0.32). For the microelements, the concentrations (in μg g^-1) obtained were As (< 1.39), Cd (< 0.10), Cu (< 0.17-5.6), Fe (8.0-50.2), Na (< 1.85), Sr (41-348), and Zn (17.3-159). Essential elements such as Ca, Mg, and Zn made good contributions to daily intake, being an alternative to meet the nutritional needs of these macroelements and microelements in humans. Principal component analysis (PCA) and hierarchical cluster analysis (HCA) were used to evaluate the results, obtaining trends between the samples in relation to their mineral composition.

Sustainable Application of Biosorption and Bioaccumulation of Persistent Pollutants in Wastewater Treatment: Current Practice

Persistent toxic substances including persistent organic pollutants and heavy metals have been released in high quantities in surface waters by industrial activities. Their presence in environmental compartments is causing harmful effects both on the environment and human health. It was shown that their removal from wastewaters using conventional methods and adsorbents is not always a sustainable process. In this circumstance, the use of microorganisms for pollutants uptake can be seen as being an environmentally-friendly and cost-effective strategy for the treatment of industrial effluents. However, in spite of their confirmed potential in the remediation of persistent pollutants, microorganisms are not yet applied at industrial scale. Thus, the current paper aims to synthesize and analyze the available data from literature to support the upscaling of microbial-based biosorption and bioaccumulation processes. The industrial sources of persistent pollutants, the microbial mechanisms for pollutant uptake and the significant results revealed so far in the scientific literature are identified and covered in this review. Moreover, the influence of different parameters affecting the performance of the discussed systems and also very important in designing of treatment processes are highly considered. The analysis performed in the paper offers an important perspective in making decisions for scaling-up and efficient operation, from the life cycle assessment point of view of wastewater microbial bioremediation. This is significant since the sustainability of the microbial-based remediation processes through standardized methodologies such as life cycle analysis (LCA), hasn’t been analyzed yet in the scientific literature.

Metal specificity of the Ni(II) and Zn(II) binding sites of the N-terminal and G-domain of E. coli HypB

HypB is one of the chaperones required for proper nickel insertion into [NiFe]-hydrogenase. Escherichia coli HypB has two potential Ni(II) and Zn(II) binding sites-the N-terminal one and the so-called GTPase one. The metal-loaded HypB-SlyD metallochaperone complex activates nickel release from the N-terminal HypB site. In this work, we focus on the metal selectivity of the two HypB metal binding sites and show that (i) the N-terminal region binds Zn(II) and Ni(II) ions with higher affinity than the G-domain and (ii) the lower affinity G domain binds Zn(II) more effectively than Ni(II). In addition, the high affinity N-terminal domain, both in water and membrane mimicking SDS solution, has a larger affinity towards Zn(II) than Ni(II), while an opposite situation is observed at basic pH; at pH 7.4, the affinity of this region towards both metals is almost the same. The N-terminal HypB region is also more effective in Ni(II) binding than the previously studied SlyD metal binding regions. Considering that the nickel chaperone SlyD activates the release of nickel and blocks the release of zinc from the N-terminal high-affinity metal site of HypB, we may speculate that such pH-dependent metal affinity might modulate HypB interactions with SlyD, being dependent on both pH and the protein's metal status.

Uptake, translocation, weathering and speciation of gold nanoparticles in potato, radish, carrot and lettuce crops

Extensive use of nanomaterials in agriculture will inevitably lead to their release to the environment in significant loads. Thus, understanding the fate of nanoparticles in the soil-plant environment, and potential presence and consequent implication of nanoparticles in food and feed products, is required. We study plant uptake of gold nanoparticles from soil, and their distribution, translocation and speciation (in terms of particle size change and release of ionic Au) in the different plant tissues of four important crops (potato, radish, carrot and lettuce). Our new analytical protocol and experiments show the feasibility of determining the presence, concentration and distribution of nanoparticles in different plant parts, which differ from plant to plant. Critically, we identify the evident capacity of plants to break down (or substantially change the properties of) nanoparticles in the rhizosphere prior to uptake, as well as the evident capacity of plants to reorganize ionic metals as nanoparticles in their tissues. This could lead to nanoparticle exposure through consumption of crops.

EST-SSR-based landscape genetics of Pseudotaxus chienii, a tertiary relict conifer endemic to China

Pseudotaxus chienii, belonging to the monotypic genus Pseudotaxus (Taxaceae), is a relict conifer endemic to China. Its populations are usually small and patchily distributed, having a low capacity of natural regeneration. To gain a clearer understanding of how landscape variables affect the local adaptation of P. chienii, we applied EST-SSR markers in conjunction with landscape genetics methods: (a) to examine the population genetic pattern and spatial genetic structure; (b) to perform genome scan and selection scan to identify outlier loci and the associated landscape variables; and (c) to model the ecological niche under climate change. As a result, P. chienii was found to have a moderate level of genetic variation and a high level of genetic differentiation. Its populations displayed a significant positive relationship between the genetic and geographical distance (i.e., "isolation by distance" pattern) and a strong fine-scale spatial genetic structure within 2 km. A putatively adaptive locus EMS6 (functionally annotated to cellulose synthase A catalytic subunit 7) was identified, which was found significantly associated with soil Cu, K, and Pb content and the combined effects of temperature and precipitation. Moreover, P. chienii was predicted to experience significant range contractions in future climate change scenarios. Our results highlight the potential of specific soil metal content and climate variables as the driving force of adaptive genetic differentiation in P. chienii. The data would also be useful to develop a conservation action plan for P. chienii.

Impact of Zinc Excess on Germination, Growth Parameters and Oxidative Stress of Sweet Basil (Ocimum basilicum L.)

In the present study, the effects of elevated zinc concentrations on germination, physiological and biochemical parameters were investigated in basil (Ocimum basilicum L.). Results indicate that zinc excess (1-5 mM ZnSO₄) did not affect germination process, but it drastically reduced vigor index and radicle elongation, and induced oxidative stress. Exposure of basil plants to 400 and 800 µM Zn decreased aerial parts and roots dry biomass, root length and leaf number. Under these conditions, the reduction of plant growth was associated with the formation of branched and abnormally shaped brown roots. Translocation factor < 1 and bioconcentration factor > 1 was observed for 100 µM Zn suggested the possible use of basil as a phytostabiliser. Excess of Zn supply (> 100 µM) decreased chlorophyll content, total phenol and total flavonoid contents. Additionally, an increased TBARS levels reflecting an oxidative burst was observed in Zn-treated plants. These findings suggest that excess Zn adversely affects plant growth, photosynthetic pigments, phenolic and flavonoid contents, and enhances oxidative stress in basil plants.