Hydrophilic Fraction of Dissolved Organic Matter Largely Facilitated Microplastics Photoaging: Insights from Redox Properties and Reactive Oxygen Species.

Dissolved organic matter (DOM) exists widely in natural water, which inevitably influences microplastic (MP) photoaging. Nevertheless, the impacts of DOM fractions with diverse molecular structures on MP photoaging remain to be elucidated. This study explored the photoaging mechanisms of polylactic acid (PLA)-MPs and polystyrene (PS)-MPs in the presence of DOM and its subfractions (hydrophobic acid (HPOA), hydrophobic neutral (HPON), and hydrophilic (HPI)). Across DOM fractions, HPI exhibited the highest electron accepting capacity (23 µmol e- (mg C)-1) due to its abundant tannin-like species (36.8%) with carboxylic groups, which facilitated more reactive oxygen species generation (particularly hydroxyl radical), leading to the strongest photoaging rate of two MPs by HPI. However, the sequences of bond cleavage during photoaging of each MPs were not clearly shifted as revealed by two-dimensional infrared correlation spectra. Inconspicuous effects on the extent of PS- and PLA-MPs photoaging were observed for HPOA and HPON, respectively. This was mainly ascribed to the occurrence of inhibitory mechanisms (e.g., light-shielding and quenching effect) counteracting the reactive oxygen species-promoting effects. The findings identified the HPI fraction of DOM for promoting PS- and PLA-MPs photoaging rate and first constructed a link among DOM molecular structures, redox properties, and effects on MP photoaging.

Size Effects of Copper Oxide Nanoparticles on Boosting Soybean Growth via Differentially Modulating Nitrogen Assimilation.

Nanoscale agrochemicals have been widely used in sustainable agriculture and may potentially affect the nitrogen fixation process in legume crops. The present study investigated the size-effects of copper oxide nanoparticles (CuO NPs) on nitrogen assimilation in soybean (G. max (L.) Merrill) plants, which were treated with different sizes (20 and 50 nm) of CuO NPs at low use doses (1 and 10 mg/kg) for 21 days under greenhouse conditions. The results showed that 50 nm CuO NPs significantly increased the fresh biomass more than 20 nm CuO NPs achieved at 10 mg/kg. The activities of N assimilation-associated enzymes and the contents of nitrogenous compounds, including nitrates, proteins, and amino acids, in soybean tissues were greatly increased across all the CuO NP treatments. The use doses of two sizes of CuO NPs had no impact on the Cu contents in shoots and roots but indeed increased the Cu contents in soils in a dose-dependent fashion. Overall, our findings demonstrated that both 20 and 50 nm CuO NPs could positively alter soybean growth and boost N assimilation, furthering our understanding that the application of nanoscale micro-nutrient-related agrochemicals at an optimal size and dose will greatly contribute to increasing the yield and quality of crops.

Quantum dots: next shift to combat plant diseases.

Plant diseases caused by microbial pathogens significantly reduce agriculture productivity and worsen food insecurity. Recently, Qiu et al. revealed that polyethyleneimine (PEI)-coated MXene quantum dots (QDs) improve tolerance in cotton seedlings against Verticillium wilt disease by maintaining oxidative system homeostasis. This finding shows how customized QDs can be used to enhance crop disease resistance.

Novel Defluorination Pathways of Perfluoroether Compounds (GenX): α-Fe2O3 Nanoparticle Layer Retains Higher Concentrations of Effective Hydrated Electrons.

The development of efficient defluorination technology is an important issue because the kind of emerging pollutant of hexafluoropropylene oxide dimer acid (GenX) as an alternative to perfluorooctanoic acid (PFOA) has the higher environmental risks. In the UV/bisulfite system, we first developed a hydrophobic confined α-Fe2O3 nanoparticle layer rich in oxygen vacancies, which accelerated the enrichment of HSO3- and GenX on the surface and pores through electrostatic attraction and hydrophobic interaction, retaining more hydrated electrons (eaq-) and rapidly destroying GenX under UV excitation. Especially, under anaerobic and aerobic conditions, the degradation percentage of GenX obtain nearly 100%, defluorination of GenX to 88 and 57% respectively. It was amazed to find that the three parallel H/F exchange pathways triggered by the rapid reactions of eaq- and GenX, which were unique to anaerobic conditions, improved the efficiency of fluoride removal and weaken the interference of dissolved oxygen and H+. Therefore, this study provided an available material and mechanism for sustainable fluoride removal from wastewater in aerobic and anaerobic conditions.

Nanoplastics Affect the Bioaccumulation and Gut Toxicity of Emerging Perfluoroalkyl Acid Alternatives to Aquatic Insects (Chironomus kiinensis): Importance of Plastic Surface Charge.

Persistent organic pollutants (POPs) have been widely suggested as contributors to the aquatic insect biomass decline, and their bioavailability is affected by engineered particles. However, the toxicity effects of emerging ionizable POPs mediated by differentially charged engineered nanoparticles on aquatic insects are unknown. In this study, 6:2 chlorinated polyfluoroalkyl ether sulfonate (F-53B, an emerging perfluoroalkyl acid alternative) was selected as a model emerging ionizable POP; the effect of differentially charged nanoplastics (NPs, 50 nm, 0.5 g/kg) on F-53B bioaccumulation and gut toxicity to Chironomus kiinensis were investigated through histopathology, biochemical index, and gut microbiota analysis. The results showed that when the dissolved concentration of F-53B remained constant, the presence of NPs enhanced the adverse effects on larval growth, emergence, gut oxidative stress and inflammation induced by F-53B, and the enhancement caused by positively charged NP-associated F-53B was stronger than that caused by the negatively charged one. This was mainly because positively charged NPs, due to their greater adsorption capacity and higher bioavailable fraction of associated F-53B, increased the bioaccumulation of F-53B in larvae more significantly than negatively charged NPs. In addition, positively charged NPs interact more easily with gut biomembranes and microbes with a negative charge, further increasing the probability of F-53B interacting with gut biomembranes and microbiota and thereby aggravating gut damage and key microbial dysbacteriosis related to gut health. These findings demonstrate that the surface charge of NPs can regulate the bioaccumulation and toxicity of ionizable POPs to aquatic insects.

Flooding regimes alleviate lead toxicity and enhance phytostabilization of salix: Evidence from physiological responses and iron-plaque formation.

Aggravated metal pollution in wetland and riparian zones has become a global environmental issue, necessitating the identification of sustainable remediation approaches. Salix exhibits great potential as a viable candidate for metal(loid) remediation. However, the underlying mechanisms for its effectiveness in different flooding regimes with Pb pollution have not been extensively studied. In this study, fast-growing Salix×jiangsuensis 'J172' was selected and planted in different Pb polluted soils (control, 400 and 800 mg ∙ kg-1) under non-flooded and flooded (CF: continuous flooding and IF: intermittent flooding) conditions for 60 days. This study aimed to explore the effects of flooding on Salix growth performance, physiological traits, and the relationship between Pb uptake/translocation and root Fe plaques. Salix×jiangsuensis 'J172' exhibited excellent tolerance and adaptation to Pb pollution with a tolerance index (TI) exceeding 0.6, even at the highest Pb levels. Moreover, the TIs under flooded conditions were higher than that under non-flooded conditions, suggesting that flooding could alleviate Pb toxicity under co-exposure to Pb and flooding. Leaf malondialdehyde (MDA) exhibited a dose-dependent response to Pb exposure; however, CF or IF mitigated the oxidative damage induced by Pb toxicity with decreased MDA content (2.2-11.9%). The superoxide dismutase and peroxidase activities were generally enhanced by flooding, but combined stress (flooding and Pb) significantly decreased catalase activity. Pb was predominantly accumulated in Salix roots, and flooding markedly increased root Pb accumulation by 19.2-173.0% compared to non-flooded condition. Additionally, a significant positive correlation was observed between the iron (Fe) content of the root plaque and root Pb accumulation, indicating that the formation of Fe plaque on the root surface could enhance the phytostabilization of Pb in Salix. The current findings highlight that fast-growing woody plants are suitable for phyto-management of metal-polluted wetlands and can potentially minimize the risk of metal mobility in soils.

Microplastics alter soil structure and microbial community composition.

Microplastics (MPs), including conventional hard-to-biodegrade petroleum-based and faster biodegradable plant-based ones, impact soil structure and microbiota in turn affecting the biodiversity and functions of terrestrial ecosystems. Herein, we investigated the effects of conventional and biodegradable MPs on aggregate distribution and microbial community composition in microhabitats at the aggregate scale. Two MP types (polyethylene (PE) and polylactic acid (PLA) with increasing size (50, 150, and 300 µm)) were mixed with a silty loam soil (0-20 cm) at a ratio of 0.5 % (w/w) in a rice-wheat rotation system in a greenhouse under 25 °C for one year. The effects on aggregation, bacterial communities and their co-occurrence networks were investigated as a function of MP aggregate size. Conventional and biodegradable MPs generally had similar effects on soil aggregation and bacterial communities. They increased the proportion of microaggregates from 17 % to 32 %, while reducing the macroaggregates from 84 % to 68 %. The aggregate stability decreased from 1.4 mm to 1.0-1.1 mm independently of MP size due to the decline in the binding agents gluing soil particles (e.g., microbial byproducts and proteinaceous substances). MP type and amount strongly affected the bacterial community structure, accounting for 54 % of the variance. Due to less bioavailable organics, bacterial community composition within microaggregates was more sensitive to MPs addition compared to macroaggregates. Co-occurrence network analysis revealed that MPs exacerbated competition among bacteria and increased the complexity of bacterial networks. Such effects were stronger for PE than PLA MPs due to the higher persistence of PE in soils. Proteobacteria, Bacteroidetes, Chloroflexi, Actinobacteria, and Gemmatimonadetes were the keystone taxa in macroaggregates, while Actinobacteria and Chloroflexi were the keystone taxa in microaggregates. Proteobacteria, Actinobacteria, and Chloroflexi were the most sensitive bacteria to MPs addition. Overall, both conventional and biodegradable MPs reduced the portion of large and stable aggregates, altering bacterial community structures and keystone taxa, and consequently, the functions.

Nano-biochar as a potential amendment for metal(loid) remediation: Implications for soil quality improvement and stress alleviation.

Metal(loid) contamination of agricultural soils has become an alarming issue due to its detrimental impacts on soil health and global agricultural production. Therefore, environmentally sustainable and cost-effective solutions are urgently required for soil remediation. Biochar, particularly nano-biochar, exhibits superior and high-performance capabilities in the remediation of metal(loid)-contaminated soil, owing to its unique structure and large surface area. Current researches on nano-biochar mainly focus on safety design and property improvement, with limited information available regarding the impact of nano-biochar on soil ecosystems and crop defense mechanisms in metal(loid)-contaminated soils. In this review, we systematically summarized recent progress in the application of nano-biochar for remediation of metal(loid)-contaminated soil, with a focus on possible factors influencing metal(loid) uptake and translocation in soil-crop systems. Additionally, we conducted the potential/related mechanisms by which nano-biochar can mitigate the toxic impacts of metal(loid) on crop production and security. Furthermore, the application of nano-biochar in field trials and existing challenges were also outlined. Future studies should integrate agricultural sustainability and ecosystem health targets into biochar design/selection. This review highlighted the potential of nano-biochar as a promising soil amendment for enhancing the remediation of metal(loid)-contaminated agricultural soils, thereby promoting the synthesis and development of highly efficient nano-biochar towards achieving environmental sustainability.

Nanoscale ZnO Improves the Amino Acids and Lipids in Tomato Fruits and the Subsequent Assimilation in a Simulated Human Gastrointestinal Tract Model.

With the widespread use of nanoenabled agrochemicals, it is essential to evaluate the food safety of nanomaterials (NMs)-treated vegetable crops in full life cycle studies as well as their potential impacts on human health. Tomato seedlings were foliarly sprayed with 50 mg/L ZnO NMs, including ZnO quantum dots (QDs) and ZnO nanoparticles once per week over 11 weeks. The foliar sprayed ZnO QDs increased fruit dry weight and yield per plant by 39.1% and 24.9, respectively. It also significantly increased the lycopene, amino acids, Zn, B, and Fe in tomato fruits by 40.5%, 15.1%, 44.5%, 76.2%, and 12.8%, respectively. The tomato fruit metabolome of tomatoes showed that ZnO NMs upregulated the biosynthesis of unsaturated fatty acids and sphingolipid metabolism and elevated the levels of linoleic and arachidonic acids. The ZnO NMs-treated tomato fruits were then digested in a human gastrointestinal tract model. The results of essential mineral release suggested that the ZnO QDs treatment increased the bioaccessibility of K, Zn, and Cu by 14.8-35.1% relative to the control. Additionally, both types of ZnO NMs had no negative impact on the α-amylase, pepsin, and trypsin activities. The digested fruit metabolome in the intestinal fluid demonstrated that ZnO NMs did not interfere with the normal process of human digestion. Importantly, ZnO NMs treatments increased the glycerophospholipids, carbohydrates, amino acids, and peptides in the intestinal fluids of tomato fruits. This study suggests that nanoscale Zn can be potentially used to increase the nutritional value of vegetable crops and can be an important tool to sustainably increase food quality and security.

Root Exposure of Graphitic Carbon Nitride (g-C3N4) Modulates Metabolite Profile and Endophytic Bacterial Community to Alleviate Cadmium- and Arsenate-Induced Phytotoxicity to Rice (Oryza sativa L.).

To investigate the mechanisms by which g-C3N4 alleviates metal(loid)-induced phytotoxicity, rice seedlings were exposed to 100 and 250 mg/kg graphitic carbon nitride (g-C3N4) with or without coexposure to 10 mg/kg Cd and 50 mg/kg As for 30 days. Treatment with 250 mg/kg g-C3N4 significantly increased shoot and root fresh weight by 22.4-29.9%, reduced Cd and As accumulations in rice tissues by 20.6-26.6%, and elevated the content of essential nutrients (e.g., K, S, Mg, Cu, and Zn) compared to untreated controls. High-throughput sequencing showed that g-C3N4 treatment increased the proportion of plant-growth-promoting endophytic bacteria, including Streptomyces, Saccharimonadales, and Thermosporothrix, by 0.5-3.30-fold; these groups are known to be important to plant nutrient assimilation, as well as metal(loid) resistance and bioremediation. In addition, the population of Deinococcus was decreased by 72.3%; this genus is known to induce biotransformation As(V) to As(III). Metabolomics analyses highlighted differentially expressed metabolites (DEMs) involved in the metabolism of tyrosine metabolism, pyrimidines, and purines, as well as phenylpropanoid biosynthesis related to Cd/As-induced phytotoxicity. In the phenylpropanoid biosynthesis pathway, the increased expression of 4-coumarate (1.13-fold) and sinapyl alcohol (1.26-fold) triggered by g-C3N4 coexposure with Cd or As played a critical role in promoting plant growth and enhancing rice resistance against metal(loid) stresses. Our findings demonstrate the potential of g-C3N4 to enhance plant growth and minimize the Cd/As-induced toxicity in rice and provide a promising nanoenabled strategy for remediating heavy metal(loid)-contaminated soil.

Differentially Charged Nanoplastics Induce Distinct Effects on the Growth and Gut of Benthic Insects (Chironomus kiinensis) via Charge-Specific Accumulation and Perturbation of the Gut Microbiota.

Nanoplastics (NPs), as an emerging contaminant, have usually been found charged in the environment, posing threats to aquatic animals. However, the underlying mechanisms governing the gut toxicity of differentially charged NPs to benthic insects are not well understood. In this study, the gut toxicity in larvae of Chironomus kiinensis exposed to negatively charged NPs (PS-COOH, 50 nm) and positively charged NPs (PS-NH2, 50 nm) at 0.1 and 1 g/kg was investigated through fluorescence imaging, histopathology, biochemical approaches, and 16S rRNA sequencing. The results showed that PS-NH2 caused more adverse effect on the larval growth performance and induced more severe oxidative stress, epithelial damage, and inflammatory responses in the gut than PS-COOH. The stronger impact caused by PS-NH2 was because the gut accumulated PS-NH2 more readily than PS-COOH for its negatively charged cell membrane. In addition, PS-NH2 were less agglomerated compared with PS-COOH, leading to an increased interaction with gut cell membranes and microbiota. Furthermore, alpha diversity and relative abundance of the keystone microbiota related to gut barrier and nutrient absorption were markedly lower exposed to PS-NH2 than PS-COOH, indirectly exacerbating stronger gut and growth damage. This study provides novel insights into the effect mechanisms underlying differentially charged NPs on benthic insects.

Aloe Vera Extract Gel-Biosynthesized Selenium Nanoparticles Enhance Disease Resistance in Lettuce by Modulating the Metabolite Profile and Bacterial Endophytes Composition.

The use of nanotechnology to suppress crop diseases has attracted significant attention in agriculture. The present study investigated the antifungal mechanism by which aloe vera extract gel-biosynthesized (AVGE) selenium nanoparticles (Se NPs) suppressed Fusarium-induced wilt disease in lettuce (Lactuca sativa). AVGE Se NPs were synthesized by utilizing sodium selenite as a Se source and AVGE as a biocompatible capping and reducing agent. Over 21 d, 2.75% of total AVGE Se NPs was dissolved into Se ions, which was more than 8-fold greater than that of bare Se NPs (0.34%). Upon exposure to soil applied AVGE Se NPs at 50 mg/kg, fresh shoot biomass was significantly increased by 61.6 and 27.8% over the infected control and bare Se NPs, respectively. As compared to the infected control, the shoot levels of citrate, isocitrate, succinate, malate, and 2-oxo-glutarate were significantly upregulated by 0.5-3-fold as affected by both Se NPs. In addition, AVGE Se NPs significantly increased the shoot level of khelmarin D, a type of coumarin, by 4.40- and 0.71-fold over infected controls and bare Se NPs, respectively. Additionally, AVGE Se NPs showed greater upregulation of jasmonic acid and downregulation of abscisic acid content relative to bare Se NPs in diseased shoots. Moreover, the diversity of bacterial endophytes was significantly increased by AVGE Se NPs, with the values of Shannon index 40.2 and 9.16% greater over the infected control and bare Se NPs. Collectively, these findings highlight the significant potential of AVGE Se NPs as an effective and biocompatible strategy for nanoenabled sustainable crop protection.

Mechanistic Understanding toward the Maternal Transfer of Nanoplastics in Daphnia magna.

Nanoplastics induce transgenerational toxicity to aquatic organisms, but the specific pathways for the maternal transfer of nanoplastics remain unclear. Herein, laser scanning confocal microscopy (LSCM) observations identified the specific pathways on the maternal transfer of polystyrene (PS) nanoplastics (25 nm) in Daphnia magna. In vivo and in vitro experiments showed that PS nanoplastics could enter the brood chamber through its opening and then be internalized to eggs and embryos using LSCM imaging (pathway I). In addition, PS nanoplastics were observed in the oocytes of the ovary, demonstrating gut-ovary-oocyte transfer (pathway II). Furthermore, label-free hyperspectral imaging was used to detect the distribution of nanoplastics in the embryos and ovary of Daphnia, again confirming the maternal transfer of nanoplastics through the two pathways mentioned above. The contribution from pathway I (88%) was much higher than pathway II (12%) based on nanoflow cytometry quantification. In addition, maternal transfer in Daphnia depended on the particle size of PS nanoplastics, as demonstrated by using LSCM and hyperspectral imaging. Unlike 25 nm nanoplastics, 50 nm PS nanoplastics could enter the brood chamber and the eggs/embryos (pathway I), but were not detected in the ovary (pathway II); 100 nm PS nanoplastics were difficult to be internalized by eggs/embryos and could not enter the ovary either. These findings provide insight into the maternal transfer mechanisms of nanoplastics in Daphnia, and are critical for better understanding the transgenerational toxicity of aquatic organisms.

Mechanism insight into the facet-dependent photoaging of polystyrene microplastics on hematite in freshwater.

Hematite, as an extensive natural mineral with multiple crystal facets, profoundly affects the migration and transformation of pollutants in the natural environment. However, little is known about the photochemical behavior of microplastics on different facets of hematite in the aquatic environment. In this work, the photoaging of polystyrene microplastics (PS-MPs) on different crystal planes ({001}, {100}, and {012} facets) and related mechanisms were studied. Two-dimensional correlation spectroscopy analysis illustrated that the reaction pathways of PS-MPs photoaging on hematite tended to preferential chemical oxidization. The stronger performance of PS-MPs photoaging, expressed by particle size reduction and surface oxidation, was observed on the {012} crystal facet. Under irradiation, {012} facet-dominated hematite with a narrower bandgap (1.93 eV) reinforced the photogenerated charge carrier separation, and the lower activation energy barrier (1.41 eV calculated from density functional theory) led to effective •OH formation from water oxidation. These findings elucidate the underlying photoaging mechanism of MPs on hematite with different mineralogical phases.

Efficient photodegradation of polystyrene microplastics integrated with hydrogen evolution: Uncovering degradation pathways.

Photocatalytic microplastics (MPs) conversion into valuable products is a promising approach to alleviate MPs pollution in aquatic environments. Herein, we developed an amorphous alloy/photocatalyst composite (FeB/TiO2) that can successfully convert polystyrene (PS) MPs to clean H2 fuel and valuable organic compounds (92.3% particle size reduction of PS-MPs and 103.5 µmol H2 production in 12 h). FeB effectively enhanced the light-absorption and carrier separation of TiO2, thereby promoting more reactive oxygen species generation (especially ‧OH) and combination of photoelectrons with protons. The main products (e.g., benzaldehyde, benzoic acid, etc.) were identified. Additionally, the dominant PS-MPs photoconversion pathway was elucidated based on density functional theory calculations, by which the significant role of ‧OH was demonstrated in combination with radical quenching data. This study provides a prospective approach to mitigate MPs pollution in aquatic environments and reveals the synergistic mechanism governing the photocatalytic conversion of MPs and generation of H2 fuel.

Micro/nanoscale bone char alleviates cadmium toxicity and boosts rice growth via positively altering the rhizosphere and endophytic microbial community.

This present study investigated pork bone-derived biochar as a promising amendment to reduce Cd accumulation and alleviate Cd-induced oxidative stress in rice. Micro/nanoscale bone char (MNBC) pyrolyzed at 400 °C and 600 °C was synthesized and characterized before use. The application rates for MNBCs were set at 5 and 25 g·kg-1 and the Cd exposure concentration was 15 mg·kg-1. MNBCs increased rice biomass by 15.3-26.0% as compared to the Cd-alone treatment. Both types of MNBCs decreased the bioavailable Cd content by 27.4-54.8%; additionally, the acid-soluble Cd fraction decreased by 10.0-12.3% relative to the Cd alone treatment. MNBC significantly reduced the cell wall Cd content by 50.4-80.2% relative to the Cd-alone treatment. TEM images confirm the toxicity of Cd to rice cells and that MNBCs alleviated Cd-induced damage to the chloroplast ultrastructure. Importantly, the addition of MNBCs decreased the abundance of heavy metal tolerant bacteria, Acidobacteria and Chloroflexi, by 29.6-41.1% in the rhizosphere but had less impact on the endophytic microbial community. Overall, our findings demonstrate the significant potential of MNBC as both a soil amendment for heavy metal-contaminated soil remediation and for crop nutrition in sustainable agriculture.

The mechanism of coumarin inhibits germination of ryegrass (Lolium perenne) and its application as coumarin-carbon dots nanocomposites.

BACKGROUND: As an important plant allelochemical, coumarin can effectively inhibit the germination of various seeds. However, little is known about the inhibition mechanism of coumarin on weed seed germination. Moreover, the herbicidal activity of coumarin is needed to be improved as a natural pesticide. RESULTS: Coumarin had the highest inhibition effect on the ryegrass (Lolium perenne) seed, where coumarin disturbed the hormone pathway by decreasing the content of gibberellic acid 3, resulting in the reduction of amylase activity and consumption of starch during the germination process of ryegrass seed. Moreover, coumarin induced decreased activity of catalase and subsequently led to the accumulation of hydrogen peroxide and malondialdehyde, causing oxidative stress during the germination process of ryegrass seed. Furthermore, to enhance the herbicidal activity of coumarin, carbon dots (CDs) modified with polyetherimide were prepared, characterized, and then combined with coumarin to form coumarin-carbon dots (Cm-CDs) nanocomposites. Compared with coumarin, Cm-CDs nanocomposites significantly increased the herbicidal activity of coumarin on ryegrass, which implies that Cm-CDs nanocomposites could be used as a potential formulation to improve the herbicidal activity of coumarin. CONCLUSION: This study not only reveals the mechanism of coumarin on ryegrass germination, but also develop Cm-CDs nanocomposites to enhance the herbicidal activity of coumarin. Our findings will stimulate the application of Cm-CDs nanomaterials as an effective and environmentally friendly formulation in agriculture. © 2023 Society of Chemical Industry.

ZnO quantum dots outperform nanoscale and bulk particles for enhancing tomato (Solanum lycopersicum) growth and nutritional values.

Tomato (Solanum lycopersicum) seedlings were exposed by foliar or root applications to Zn in different nanoscale and non-nanoscale forms (40 mg Zn/L) under hydroponic conditions for 15 days. Under foliar exposure, ZnO QDs significantly promoted tomato growth, while ZnO NPs and BPs had lower impacts. ZnO QDs increased fresh weight and plant height by 42.02 % and 21.10 % relative to the untreated controls, respectively. The ionic control (ZnSO4·7H2O, 176.6 mg/L) decreased fresh weight by 39.31 %. ZnO QDs also significantly increased the Chla/Chlb ratio, as well as carotenoids and protein content by 7.70 %, 8.90 % and 26.33 %, respectively, over the untreated controls, suggesting improvement in seedling photosynthetic performance. Antioxidant enzyme (POD, PPO and PAL) activities in ZnO QDs treated shoots were significantly decreased by 31.1 %, 17.8 % and 48.3 %, respectively, indicating no overt oxidative damage from exposure. Importantly, the translocation factor of Zn (TFZn) in the foliar exposure of the ZnO QDs treatment was 73.2 %, 97.1 % and 276.9 % greater than the NPs, BPs, and ionic controls, respectively. Overall, these findings clearly demonstrate that foliar spray of nanoscale nutrients at the appropriate concentration and size can significantly increase crop growth and be a sustainable approach to nano-enabled agriculture.

The role of sulfur nutrition in plant response to metal(loid) stress: Facilitating biofortification and phytoremediation.

Metal(loid)s contamination poses a serious threat to ecosystem biosafety and human health. Phytoremediation is a cost-effective and eco-friendly technology with good public acceptance, although the process does require a significant amount of time for success. To enhance the phytoremediation efficiency, numerous approaches have been explored, including soil amendments application with chelators to facilitate remediation. Sulfur (S), a macronutrient for plant growth, plays vital roles in several metabolic pathways that can actively affect metal(loid)s phytoextraction, as well as attenuate metal(loid) toxicity. In this review, different forms of S-amendments (fertilizers) on uptake and translocation in plants upon exposure to various metal(loid) are evaluated. Possible mechanisms for S application alleviating metal(loid) toxicity are documented at the physiological, biochemical and molecular levels. Furthermore, this review highlights the crosstalk between S-assimilation and other biomolecules, such as phytohormones, polyamines and nitric oxide, which are also important for metal(loid) stress tolerance. Given the effectiveness and potential of S amendments on phytoremediation, future studies should focus on optimizing phytoremediation efficiency in long-term field studies and on investigating the appropriate S dose to maximize the food safety and ecosystem health.

The behavior, transport, and positive regulation mechanism of ZnO nanoparticles in a plant-soil-microbe environment.

ZnO nanoparticles (ZnO NPs) have been widely used in several fields, and they have the potential to be a novel fertilizer to promote plant growth. For the effective use of ZnO NPs, it is necessary to understand their influence mechanisms and key interactions with the soil physical and biological environment. In this review, we summarize the fate and transport of ZnO NPs applied via soil treatment or foliar spray in plant-soil systems and discuss their positive regulation mechanisms in plants and microbes. The latest research shows that the formation, bioavailability, and location of ZnO NPs experience complicated changes during the transport in soil-plant systems and that this depends on many factors. ZnO NPs can improve plant photosynthesis, nutrient element uptake, enzyme activity, and the related gene expression as well as modulate carbon/nitrogen metabolism, secondary metabolites, and the antioxidant systems in plants. Several microbial groups related to plant growth, disease biocontrol, and nutrient cycling in soil can be altered with ZnO NP treatment. In this work, we present a systematic comparison between ZnO NP fertilizer and conventional zinc salt fertilizer. We also fill several knowledge gaps in current studies with the hope of providing guidance for future research.