Foliar Exposure Research Articles

Screening Surface-Defective Graphene Quantum Dots: Promoting Plant Growth and Combating Phytovirus.

Reduced graphene quantum dots (r-GQD), graphene oxide quantum dots (GOQD), and carboxylated graphene quantum dots (C-GQD) are screened to promote tobacco growth and combat tobacco mosaic virus (TMV). First, a 21-day foliar exposure is employed to explore GQDs' impacts on N. benthamiana. Surface-defective GOQD and C-GQD are screened out to facilitate N. benthamiana uptake through leaf stomata, and to promote seedlings of differently leaf ages to various degrees at different concentrations after different durations of foliar exposure. Specially, compared to the ddH2O treatment, GOQD/C-GQD at 400 mg L-1 increase biomass by 44%/68%, increase chlorophyll content by 43%/54% and up-regulate the expression of growth-related genes NtLRX1, CycB, and NtPIP1 by more than two-fold. Second, different from the transient inhibition shown by r-GQD and the TMV enhancement shown by GOQD, C-GQD can directly inactivate TMV infection by inducing TMV aggregation and attachment outside TMV, significantly decreasing TMV replication and hindering TMV spread over 21-day. Specially, C-GQD decreases the transcript abundance of TMV RdRp and TMV CP to 0.11-fold and 0.29-fold, and down-regulates the host defensive response pathways. This work provides a comparative analysis of GQDs with different surface-functionalizations, highlighting C-GQD as a promising nanotechnology tool for promoting plant growth and inactivating phytovirus.

Temporal Dynamics of Copper-Based Nanopesticide Transfer and Subsequent Modulation of the Interplay Between Host and Microbiota Across Trophic Levels.

During agricultural production, significant quantities of copper-based nanopesticides (CBNPs) may be released into terrestrial ecosystems through foliar spraying, thereby posing a potential risk of biological transmission via food chains. Consequently, we investigated the trophic transfer of two commonly available commercial CBNPs, Reap2000 (RP) and HolyCu (HC), in a plant-caterpillar terrestrial food chain and evaluated impacts on host microbiota. Upon foliar exposure (with 4 rounds of spraying, totaling 6.0 mg CBNPs per plant), leaf Cu accumulation levels were 726 ± 180 and 571 ± 121 mg kg-1 for RP and HC, respectively. HC exhibited less penetration through the cuticle compared to RP (RP: 55.5%; HC: 32.8%), possibly due to size exclusion limitations. While caterpillars accumulated higher amounts of RP, HC exhibited a slightly higher trophic transfer factor (TTF; RP: 0.69 ± 0.20; HC: 0.74 ± 0.17, p > 0.05) and was more likely to be transferred through the food chain. The application of RP promoted the dispersal of phyllosphere microbes and perturbed the original host intestinal microbiota, whereas the HC group was largely host-modulated (control: 65%; RP: 94%; HC: 34%). Integrating multiomics analyses and modeling approaches, we elucidated two pathways by which plants exert bottom-up control over caterpillar health. Beyond the direct transmission of phyllosphere microbes, the leaf microbiome recruited upon exposure to CBNPs further influenced the ingestion behavior and intestinal microbiota of caterpillars via altered leaf metabolites. Elevated Proteobacteria abundance benefited caterpillar growth with RP, while the reduction of Proteobacteria with HC increased the risk of lipid metabolism issues and gut disease. The recruited Bacteroidota in the RP phyllosphere proliferated more extensively into the caterpillar gut to enhance stress resistance. Overall, the gut microbes reshaped in RP caterpillars exerted a strong regulatory effect on host health. These findings expand our understanding of the dynamic transmission of host-microbiota interactions with foliar CBNPs exposure, and provide critical insight necessary to ensure the safety and sustainability of nanoenabled agricultural strategies.

Foliar Exposure of Deuterium Stable Isotope-Labeled Nanoplastics to Lettuce: Quantitative Determination of Foliar Uptake, Transport, and Trophic Transfer in a Terrestrial Food Chain.

Nanoplastics (NPs) are widely detected in the atmosphere and are likely to be deposited on plant leaves. However, our understanding of their foliar uptake, translocation, and trophic transfer profiles is limited due to a lack of quantitative analytical tools to effectively probe mechanisms of action. Here, using synthesized deuterium (2H) stable isotope-labeled polystyrene nanoplastics (2H-PSNPs), the foliar accumulation and translocation of NPs in lettuce and the dynamics of NP transfer along a lettuce-snail terrestrial food chain were investigated. Raman imaging and scanning electron microscopy demonstrated that foliar-applied NPs aggregated on the leaf surface, entered the mesophyll tissue via the stomatal pathway, and eventually translocated to root tissues. Quantitative analysis showed that increasing levels of foliar exposure to 2H-PSNPs (0.1, 1, and 5 mg/L in spray solutions, equivalent to receiving 0.15, 1.5, and 7.5 μg/d of NPs per plant) enhanced NP accumulation in leaves, with concentrations ranging from 0.73 to 15.6 μg/g (dw), but only limited translocation (<5%) to roots. After feeding on 5 mg/L 2H-PSNP-contaminated lettuce leaves for 14 days, snails accumulated NPs at 0.33 to 10.7 μg/kg (dw), with an overall kinetic trophic transfer factor of 0.45, demonstrating trophic dilution in this food chain. The reduced ingestion rate of 3.18 mg/g/day in exposed snails compared to 6.43 mg/g/day can be attributed to the accumulation of 2H-PSNPs and elevated levels of chemical defense metabolites in the lettuce leaves, which decreased the palatability for snails and disrupted their digestive function. This study provides critical quantitative information on the characteristics of airborne NP bioaccumulation and the associated risks to terrestrial food chains.

Lettuce (Lactuca sativa L.) alters its metabolite accumulation to cope with CuO nanoparticles by promoting antioxidant production and carbon metabolism.

Copper-based nanoparticles (NPs) are gradually being introduced as sustainable agricultural nanopesticides. However, the effects of NPs on plants requires carefully evaluation to ensure their safe utilization. In this study, leaves of 2-week-old lettuce (Lactuca sativa L.) were exposed to copper oxide nanoparticles (CuO-NPs, 0 [CK], 100 [T1], and 1000 [T2] mg/L) for 15days. A significant Cu accumulation (up to 1966mg/kg) was detected in lettuce leaves. The metabolomics revealed a total of 474 metabolites in lettuce leaves, and clear differences were observed in the metabolite profiles of control and CuO-NPs treated leaves. Generally, phenolic acids and alkaloids, which are important antioxidants, were significantly increased (1.26-4.53 folds) under foliar exposure to NPs; meanwhile, all the significantly affected flavonoids were down-regulated after CuO-NP exposure, indicating these flavonoids were consumed under oxidative stress. Succinic and citric acids, which are key components of the tricarboxylic acid cycle, were especially increased under T2, suggesting the energy and carbohydrate metabolisms were enhanced under high-concentration CuO-NP treatment. There was also both up- and down-regulation of fatty acids, suggesting cell membrane fluidity and function responded to CuO-NPs. Galactinol, which is related to galactose metabolism, and xanthosine, which is crucial in purine and caffeine metabolism, were down-regulated under T2, indicating decreased stress resistance and disturbed nucleotide metabolism under the high CuO-NP dose. Moreover, the differentially accumulated metabolites were significantly associated with plant growth and its antioxidant ability. Future work should focus on controlling the overuse or excessive release of NPs into agricultural ecosystems to limit their adverse effects.

Effects of Gold Nanoparticles on Mentha spicata L., Soil Microbiota, and Human Health Risks: Impact of Exposure Routes.

Nanoparticles, due to their extensive production and application, can have significant consequences for the environment, including soil and plant pollution. Therefore, it is very important to assess how nanoparticles will affect plants depending on the exposure pathways. The effect of gold nanoparticles in a concentration range of 1-100 mg/L on Mentha spicata L. during a 28-day experiment was investigated. Two routes of nanoparticles exposure were applied: root and foliar. Transmission electron microscopy was used to characterize nanoparticles and their effect on plant leaves' ultrastructure. Gold content in soil and plant segments was determined using k0-neutron activation analysis. For root exposure, gold was mainly accumulated in soil (15.2-1769 mg/kg) followed by root systems (2.99-454 mg/kg). The maximum accumulation of gold in leaves (5.49 mg/kg) was attained at a nanoparticle concentration of 100 mg/L. Foliar exposure resulted in the maximum uptake of gold in leaves (552 mg/kg) and stems (18.4 mg/kg) at the highest applied nanoparticle concentration. The effect of nanoparticles on the Mentha spicata L. leaves' biochemical composition was assessed. Nanoparticles affected the content of chlorophyll and carotenoids and led to an increase in antioxidant activity. Root exposure to gold nanoparticles resulted in an increase in the number of starch grains in chloroplasts and also suppressed the activity of the soil microbiota. Gold extraction from mint leaves into herbal infusion varied from 2 to 90% depending on the concentration of nanoparticles in the solution and the exposure route. The health risk as a result of gold exposure via herbal tea intake was assessed through estimated daily intake. The hazard quotient values were found to be less than the cutoff, indicating that a cup of tea infusion should not cause a serious impact to human health.

Elicitation of salicylic acid and methyl jasmonate provides molecular and physiological evidence for potato susceptibility to infection by Erwinia carotovora subsp. carotovora

Among the range of severe plant diseases, bacterial soft rot caused by Erwinia carotovora is a significant threat to crops. This study aimed to examine the varying response patterns of distinct potato cultivars to the influence of E. carotovora. Furthermore, it seeks to highlight the potential role of salicylic acid (SA) and methyl jasmonate (MeJA) in stimulating the antioxidant defence system. We collected eight bacterial isolates from diseased and rotted tubers which were morphologically and physiologically identified as E. carotovora subsp. carotovora. We conducted a greenhouse experiment to analyse the antioxidant responses of three different potato cultivars (Diamont, Kara, and Karros) at various time intervals (2, 4, 6, 8, 12, and 24 h) after bacterial infection (hpi). We assessed the extent of disease damage by applying a foliar spray of 0.9 mM salicylic acid (SA) and 70 μM methyl jasmonate (MeJA). Inoculating with Ecc led to an increase in total phenolic levels, as well as the activities and gene expression of phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO) and peroxidase (POX) as time progressed. Additionally, the application of SA and MeJA resulted in a further increase relative to the diseased treatments. The Karros cultivar, unlike the Diamont and Kara cultivars, demonstrated the highest expression levels of PAL, PPO and POX through inoculation, reflecting its higher levels of activity and resistance. Furthermore, the genetic response of potato cultivars to infection at 0 hpi varied depending on their susceptibility. The examination of the rate of PAL activity upregulation following SA or MeJA stimulation clarifies the cultivars' susceptibility over time. In conclusion, the study identified E. carotovora subsp. carotovora as the most virulent isolate causing soft rot disease in potato tubers. It further revealed that the Karros cultivar displayed superior resistance with high activities and gene expression of PAL, PPO and POX, while the cv. Diamont exhibited sensitivity. Additionally, foliar exposure to SA and MeJA induced antioxidant responses, enhancing the potato plants' resistance against Ecc pathogenesis and overall plant defence.

Foliar-applied silicate potassium modulates growth, phytochemical, and physiological traits in Cichorium intybus L. under salinity stress

One of the major problems endangering plant growth and productivity worldwide is salt stress. This study aimed to assess the effects of potassium silicate (K2O3Si) on the physical, biochemical, and morphological characteristics of chicory (Cichorium intybus L.) under various levels of salinity stress. The plants were treated with K2O3Si at concentrations of 0, 1, 2, and 3 mM and cultivated under different salt stress conditions (0, 80, 160, and 240 mM NaCl). The findings revealed that salt stress led to decreased root and shoot dry weights, Fv/Fm ratio, chlorophyll a, b, and total chlorophyll, as well as inulin contents. However, foliar exposure to K2O3Si at all salinity levels resulted in improvements in the measured traits. As salinity levels increased, there was a corresponding increase in the accumulation of sodium ions (Na+) and a sharp reduction in potassium ions (K +) in the shoot. Nonetheless, treatment with K2O3Si caused a decrease in Na + accumulation and an improvement in K+ content under all salinity levels. Carotenoid content increased under 80 mM salinity stress, but decreased with higher salinity levels. Application of K2O3Si at all levels resulted in increased carotenoid content under salinity stress conditions. The content of MDA increased significantly with increasing salinity stress, particularly at 240 mM. However, foliar spraying with K2O3Si significantly decreased MDA content at all salinity levels. Salinity stress up to 160 mM increased the total phenol, flavonoid, and anthocyanin contents, while 240 mM NaCl decreased the biosynthesis of phytochemicals. Additionally, the use of K2O3Si increased the content of total phenol, flavonoid, and anthocyanin at all salt levels. Foliar application of K2O3Si increased the tolerance of chicory plants to salinity stress by reducing MDA and increasing phenolic compounds and potassium content. These results suggest that exogenous K2O3Si can be a practical strategy to improve the growth and yield of chicory plants exposed to saline environments.

Bio-formulated chitosan nanoparticles enhance disease resistance against rice blast by physiomorphic, transcriptional, and microbiome modulation of rice (Oryza sativa L.)

Rice blast disease (RBD) caused by Magnaporthe oryzae, threaten food security by cutting agricultural output. Nano agrochemicals are now perceived as sustainable, cost-effective alternatives to traditional pesticides. This study investigated bioformulation of moringa chitosan nanoparticles (M-CsNPs) and their mechanisms for suppressing RBD while minimizing toxic effects on the microenvironment. M-CsNPs, sized 46 nm with semi-spherical morphology, significantly suppressed pathogen growth, integrity, and colonization at 200 mg L−1in vitro. Greenhouse tests with foliar exposure to the same concentration resulted in a substantial 77.7 % reduction in RBD, enhancing antioxidant enzyme activity and plant health. Furthermore, M-CsNPs improved photosynthesis, gas exchange, and the nutritional profile of diseased rice plants. RNA-seq analysis highlighted upregulated defense-related genes in treated rice plants. Metagenomic study showcased reshaping of the rice microbiome, reducing Magnaporthe abundance by 93.5 %. Both healthy and diseased rice plants showed increased microbial diversity, particularly favoring specific beneficial species Thiobacillus, Nitrospira, Nocardioides, and Sphingomicrobium in the rhizosphere and Azonexus, Agarivorans, and Bradyrhizobium in the phyllosphere. This comprehensive study unravels the diverse mechanisms by which M-CsNPs interact with plants and pathogens, curbing M. oryzae damage, promoting plant growth, and modulating the rice microbiome. It underscores the significant potential for effective plant disease management.

Analysis of multiple biomarkers revealed the size matters of Cu particles for barley response under foliar exposure

The impact of particle size of engineered nanoparticles (ENPs) on plant response has marginally been investigated under the foliar application so far. Concerning the significance of particle diameter for their properties and interaction with plants, the effect of size should be considered in the analysis of the effect of micronutrient-based ENPs on plants. It is of particular importance for ENPs containing Cu due to plants needing a relatively low amount of this element, thus there is a risk of overdosing during application as a fertilizer or pesticide. Here, we examined the biochemical and transcriptional response of barley (Hordeum vulgare L.) to Cu nanoparticles (nano-Cu) with different diameters (25 nm, 50 nm, 70 nm), microparticles (micro-Cu), and chelated Cu (EDTA-Cu). The plants suffering from Cu deficiency were foliar sprayed with Cu compounds at 1000 mg/L during the tillering stage. 1- and 7-day plants were analyzed in terms of biomass, Cu content, the activity of enzymes involved with antioxidant response, the content of low molecular weight compounds, and the expression of genes regulated metal homeostasis, aquaporins, and defense. The results showed that the Cu leaf level was differentiated over time and after 7 days it was higher under exposure to the smallest nano-Cu than other particulate Cu. Regardless of the duration of exposure, the Cu content was highest in plants treated with Cu-EDTA. The cluster analysis of all markers revealed a clear distinct response to the smallest nano-Cu and other particulate and ionic treatments. The bigger nano-Cu, depending on the markers, caused the medium effects between the nano-Cu 25 nm and micro-Cu and Cu-EDTA. The found size thresholds at the nanoscale will be useful for the fabrication of safe-by-design agrochemicals to provide crop security and attenuate environmental impact.

Effects of uptake pathways on the accumulation, translocation, and metabolism of OPEs in rice: An emphasis on foliar uptake

The often-overlooked importance of foliar absorption on the plant uptake of organic pollutants was investigated by an exposure chamber test. Rice seedlings were exposed to organophosphate esters (OPEs) through 8 scenarios arranged from 3 major uptake pathways: root uptake via solution, foliar uptake via gas, and foliar uptake via particles, to identify the contributions of these 3 uptake pathways and their influences on the translocation and metabolism of OPEs in rice. The concentration of OPEs in rice tissues showed an “additive effect” with the increase of exposure pathways. OPEs in rice shoots mainly originated from foliar uptake through particle (29.6 %–63.5 %) and gaseous (28.5 %–49.4 %) absorptions rather than root uptake (7.86 %–24.2 %) under the exposure condition. In comparison with stomal absorption, wax layer penetration was the main pathway for most OPEs to enter into leaves, especially for those compounds with high octanol-air partition coefficients. Although the subcellular distributions of OPEs in the rice tissues of the foliar exposure were slightly different from those of the root exposure, hydrophobic OPEs were mainly stored in the cell wall with hydrophilic OPEs mainly in the cytosol. The translocation of OPEs from the exposed tissue to the unexposed tissue were significantly negatively correlated with their octanol-water partition coefficients, but their basipetal translocation were limited. The result suggested that the translocation of OPEs within rice is prioritized over their degradation. This study deepens our understanding of the processes behind OPE uptake by rice and highlights the importance of foliar uptake, especially for those via particle absorption.

Metabolic response of lettuce (Lactuca sativa L.) to polystyrene nanoplastics and microplastics after foliar exposure

Foliar exposure to polystyrene nanoplastics and microplastics exerted varied effects on the metabolism of lettuce (Lactuca sativa L.).

Uptake, accumulation and translocation mechanisms of organophosphate esters in cucumber (Cucumis sativus) following foliar exposure

Organophosphate esters (OPEs) have been frequently detected in crops. However, few studies have focused on the uptake and translocation of OPEs in plants following foliar exposure. Herein, to investigate the foliar uptake, accumulation and translocation mechanisms of OPEs in plant, the cucumber (Cucumis sativus) was selected as a model plant for OPEs exposure via foliar application under control conditions. The results showed that the content of OPEs in the leaf cuticle was higher than that in the mesophyll on exposed leaf. Significant positive correlations were observed between the content of OPEs in the leaf cuticle and their log Kow and log Kcw values (P < 0.01), suggesting that OPEs with high hydrophobicity could not easily move from the cuticle to the mesophyll. The moderately hydrophobic OPEs, such as tris (2-chloroisopropyl) phosphate (TCPP, log Kow = 2.59), were more likely to move not only from the cuticle to the mesophyll but also from the mesophyll to the phloem. The majority of the transported OPEs accumulated in younger leaves (32–45 %), indicating that younger tissue was the primary target organ for OPEs accumulation after foliar exposure. Compared to chlorinated OPEs (except TCPP) and aryl OPEs, alkyl OPEs exhibited the strongest transport capacity in cucumber seedling due to their high hydrophilicity. Interestingly, tri-p-cresyl phosphate was found to be more prone to translocation compared to tri-m-cresyl phosphate and tri-o-cresyl phosphate, despite having same molecular weight and similar log Kow value. These results can contribute to our understanding of foliar uptake and translocation mechanism of OPEs by plant.

Co-exposure of polystyrene microplastics influence cadmium trophic transfer along the “lettuce-snail” food chain: Focus on leaf age and the chemical fractionations of Cd in lettuce

Cadmium (Cd) and polystyrene microplastics (PS) co-contamination always occurs in environment; however, the trophic transfer of Cd and PS is still poorly understood. A hydroponic experiment was conducted to investigate the behavior of Cd in lettuce, together with the root or foliar exposure of different sized PS. Accumulation and chemical form distributions of Cd in leaves were distinguished into young and mature leaves. Subsequently, a 14-day snail feeding experiment was performed. Data showed that Cd accumulation in roots, rather than in leaves, are significantly affected by PS coexistence. However, mature leaves had a higher Cd content than young leaves under the root exposure of PS, while a reverse effect was observed in the foliar exposure. There existed a positive correlation between the food-chain transfer associated Cd (CdFi+Fii+Fiii) in mature leaves and Cd content in snail soft tissue (r = 0.705, p < 0.001), but not in young leaves. Though no bio-amplification of Cd in food chain was observed, an increase of Cd transfer factor (TF) from lettuce to snail was noted in the root exposure of 5 μm PS and the foliar exposure of 0.2 μm PS. Moreover, we observed a highest increase rate of 36.8 % in TF values from lettuce to snail viscera, and a chronic inflammatory response in snail stomach tissue. Therefore, more attentions should be paid to study the ecological risks of heavy metals and microplastics co-contamination in environment.

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.

Positively Charged Microplastics Induce Strong Lettuce Stress Responses from Physiological, Transcriptomic, and Metabolomic Perspectives.

Microplastics (MPs) can enter plants through the foliar pathway and are potential hazards to ecosystems and human health. However, studies related to the molecular mechanisms underlying the impact of foliar exposure to differently charged MPs to leafy vegetables are limited. Because the surfaces of MPs in the environment are often charged, we explored the uptake pathways, accumulation concentration of MPs, physiological responses, and molecular mechanisms of lettuce foliarly exposed to MPs carrying positive (MP+) and negative charges (MP-). MPs largely accumulated in the lettuce leaves, and stomatal uptake and cuticle entry could be the main pathways for MPs to get inside lettuce leaves. More MP+ entered lettuce leaves and induced physiological, transcriptomic, and metabolomic changes, including a decrease in biomass and photosynthetic pigments, an increase in reactive oxygen species and antioxidant activities, a differential expression of genes, and a change of metabolite profiles. In particular, MP+ caused the upregulation of circadian rhythm-related genes, and this may play a major role in the greater physiological toxicity of MP+ to lettuce, compared to MP-. These findings provide direct evidence that MPs can enter plant leaves following foliar exposure and a molecular-scale perspective on the response of leafy vegetables to differently charged MPs.

Nanoparticle's uptake and translocation mechanisms in plants via seed priming, foliar treatment, and root exposure: a review.

Nanotechnology is one of the promising techniques and shares wide ranges of applications almost in every field of life. Nanomaterials are getting continuous attractions due to specific physical and chemical properties and being applied as multifunctional material. The use of nanomaterials/nanoparticles in agriculture sector for crop improvement and protection against various environmental threats have attained greater significance. Size and nature of nanoparticles, mode of application, environmental conditions, rhizospheric and phyllospheric environment, and plant species are major factors that influence the action of nanoparticles. The mode or method of nanoparticle applications to plants is attaining greater attentions. Recently, different methods for nanoparticle applications (seed priming, foliar, and root application) are being used to improve crop growth. It is of quite worth that which method is suitable for nanoparticle application, and how nanoparticles can possibly translocate to various plant tissues from root to shoot or vice versa. These information's are poorly understood and need more investigations to explore the comprehensive mechanism by which nanoparticles make their possible entry through different plant organs and how they transport to regulate various physiological and molecular functions in plant cells. Therefore, this study comprehensively provides the knowledge of nanoparticles uptake via seed priming, foliar exposure, and root application, and their possible translocation mechanism within plants influenced by various factors that has not clearly presented. This study will provide new insights to find out an actual uptake and translocation mechanism of nanoparticles that may help researchers to develop nanoparticle-based new strategies for plants to cope with various environmental challenges. This study also focuses on different soil factors or above ground factors that areinvolved in nanoparticles uptake and translocation and ultimately their functioning in plants.

Surface Coated Sulfur Nanoparticles Suppress Fusarium Disease in Field Grown Tomato: Increased Yield and Nutrient Biofortification.

Little is known about the effect of nano sulfur (NS) under field conditions as a multifunctional agricultural amendment. Pristine and surface coated NS (CS) were amended in soil at 200 mg/kg that was planted with tomato (Solanum lycopersicum) and infested with Fusarium oxysporum f. sp. lycopersici. Foliar exposure of CS (200 μg/mL) was also included. In healthy plants, CS increased tomato marketable yield up to 3.3∼3.4-fold compared to controls. In infested treatments, CS significantly reduced disease severity compared to the other treatments. Foliar and soil treatment with CS increased yield by 107 and 192% over diseased controls, respectively, and significantly increased fruit Ca, Cu, Fe, and Mg contents. A $33/acre investment in CS led to an increase in marketable yield from 4920 to 11,980 kg/acre for healthy plants and from 1135 to 2180 kg/acre for infested plants, demonstrating the significant potential of this nanoenabled strategy to increase food production.

Contamination of useful plant leaves with chromium and other potentially toxic elements and associated health risks in a polluted mining-smelting region of South Africa

• Foliar Al, Co, Cr and Hg concentrations exceeded international permissible levels. • Cr(VI) was detected in unwashed leaves and soils from outcrops and polluted sites. • Among all PTEs, only Cr had a Hazard Quotient value > 1 for unwashed leaves. • Estimated weekly intake of Hg exceeded recommended PTWI. • Carcinogenic risks were high for Cr(VI), total Cr and Ni. Foliar exposure to dust-borne potentially toxic elements (PTEs) is often overlooked in chromium (Cr) mining and industrial regions. A comparative analysis of unwashed (UL) and washed leaves (WL) was conducted to investigate the contribution of dust to Al, As, Cd, Co, Cr (total and hexavalent Cr (Cr(VI)), Cu, Hg, Mn, Mo, Ni, Pb, Sb, V and Zn contents of leafy vegetables and medicinal plants from chromitite outcrops and Cr mining-smelting localities in Sekhukhuneland, South Africa. For leafy vegetables, health risks were estimated for all PTEs except Al and Hg, for which weekly intakes were calculated. Mean total Cr levels in UL and WL exceeded the international permissible levels by up to 22- and 9-fold, respectively, linking foliar Cr contamination to dust deposition and a lesser extent, accumulation in tissue. The most hazardous Cr species, Cr(VI) was detected in soil-plant (UL) systems of outcrops and polluted sites. Unwashed leaves had higher mean concentrations of 71% of the assessed PTEs (except Cd, Co, Hg and Sb) than WL, indicating dust as a source of PTEs. Only Cr had a Hazard Quotient (HQ) > 1 (UL). The HQ of Cr and Co contributed the most to the Hazard Index of UL (1.70) and WL (1.39). Carcinogenic risk was > 1 × 10 ‒4 for Cr(VI) (UL) and > 1 × 10 ‒3 for total Cr (UL > WL) and Ni (WL > UL). Estimated weekly intake of Hg (WL > UL) exceeded Provisional Tolerable Weekly Intake. Lifelong consumption of unwashed and even washed leafy vegetables might be hazardous in the study locality. Regular monitoring of PTE levels in the dust-soil-plant system is necessary for Cr mining-smelting regions.

Effect of foliar and root exposure to polymethyl methacrylate microplastics on biochemistry, ultrastructure, and arsenic accumulation in Brassica campestris L.

Despite the serious risk of microplastic pollution in the roots and leaves of crops, the phytotoxicity of microplastics (introduced via different exposure routes) in leafy vegetables remain insufficiently understood. Here, the effects of the root and foliar exposure of polymethyl methacrylate microplastic (PMMAMPs) on phytotoxicity, As accumulation, and subcellular distribution were investigated in rapeseed (Brassica campestris L). The relative chlorophyll content under PMMAMPs treatment decreased with time, and the 0.05 g L−1 root exposure decreased it significantly (by 9.97–20.48%, P < 0.05). In addition, superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and ascorbate peroxidase (APX) activities in rapeseed were more sensitive to PMMAMPs introduced through root exposure than through foliar exposure. There was dose-dependent ultrastructural damage, and root exposure had a greater impact than foliar exposure on root tip cells and chloroplasts. PMMAMPs entered the shoots and roots of rapeseed through root exposure. Under foliar exposure, PMMAMPs promoted As accumulation in rapeseed by up to 75.6% in shoots and 68.2% in roots compared to that under control (CK). As content in cell wall under PMMAMP treatments was 3.6–5.3 times higher than that of CK, as indicated by subcellular component results. In general, root exposure to PMMAMPs resulted in a stronger physiological impact and foliar exposure led to increased As accumulation in rapeseed.

Manufactured Nano-Objects Confer Viral Protection against Cucurbit Chlorotic Yellows Virus (CCYV) Infecting Nicotiana benthamiana.

Nanotechnology has emerged as a new tool to combat phytopathogens in agricultural crops. Cucurbit chlorotic yellows virus (CCYV) mainly infects Solanaceae crops and causes significant crop losses. Nanomaterials (NMs) may have efficacy against plant viruses, but the mechanisms underlying complex nanomaterials-plant-virus interactions remain elusive. We challenged Nicotiana benthamiana plants with GFP-tagged CCYV and observed morphological, physiological, and molecular changes in response to 21-d foliar exposure to nanoscale Fe and Zn and C60 fullerenes at 100 mg/L concentration for 21 days. We observed that in response to C60 (100 mg/L) treatment, plants displayed a normal phenotype while the viral infection was not seen until 5 days post-inoculation. On the contrary, Fe and Zn were unable to suppress viral progression. The mRNA transcriptional analysis for GFP and viral coat protein revealed that the transcripts of both genes were 5-fold reduced in response to C60 treatment. Evaluation of the chloroplast ultrastructure showed that NMs treatment maintained the normal chloroplast structure in the plants as compared to untreated plants. C60 upregulated the defense-related phytohormones (abscisic acid and salicylic acid) by 42–43%. Our results demonstrate the protective function of carbon-based NMs, with suppression of CCYV symptoms via inhibition of viral replication and systemic movement.