Characterization of Root and Foliar-Applied Iron Oxide Nanoparticles (α-Fe2O3, γ-Fe2O3, Fe3O4, and Bulk Fe3O4) in Improving Maize (Zea mays L.) Performance

Enhancing Germination and Growth of Chrysanthemum Synthetic Seeds Through Iron Oxide Nanoparticles and Indole-3-Acetic Acid: Impact of Treatment Duration on Metabolic Activity and Genetic Stability

Background

This study investigated the effects of pure iron oxide nanoparticles (Fe3O4 NPs), citrate-stabilized iron oxide nanoparticles (Fe3O4CA NPs), and indole-3-acetic acid (IAA), applied at various time regimes, on the germination, growth, and ex vitro development of chrysanthemum synthetic seeds. The genetic and metabolic stability of the plants was also assessed.

Methods

Nodal segments of Chrysanthemum × morifolium /Ramat./ Hemsl. 'Richmond', with a single axillary bud, were encapsulated in 3% calcium alginate with the addition of IAA (1 mg·L-1) and/or NPs (7.7 mg·L-1). The synthetic seeds were cultured in vitro for 30 or 60 days on a water-agar medium and then transplanted to the greenhouse for further analyses.

Results

Results indicated that IAA and Fe3O4CA NPs applied singularly significantly enhanced germination rates (83.33-92.18%) compared with the IAA- and NP-free control (56.67-64.18%), regardless of treatment time. The simultaneous use of IAA and Fe3O4CA NPs promoted longer shoot development after 30 days of treatment but showed negative effects after extended exposure. The same combination improved rooting efficiency compared to IAA alone. Supplementation with NPs improved acclimatization rates for younger plants but had variable effects on older plants. Leaf growth metrics were enhanced with Fe3O4CA NPs in plants after 30 days of treatment, yet no significant differences were observed in leaf dimensions after 60 days. The content of flavonoids, anthocyanins, and chlorophyll was affected by the exposure duration. Biochemical analyses revealed increased total polyphenol content and antioxidant capacity (FRAP, ABTS) in treated plants, particularly with IAA and Fe3O4CA NPs. Start codon targeted (SCoT) analyses showed no polymorphisms among treated plants, confirming their genetic stability.

Conclusion

The study found that the combination of IAA and Fe3O4CA NPs improved germination and shoot development in chrysanthemum synthetic seeds, while maintaining genetic stability, although prolonged exposure negatively affected plant growth metrics.

Magnetite nanoparticles (Fe3O4NPs) promote drought tolerance and improve plant health, grain quality and yield in kidney bean (Phaseolus vulgaris L.)

As a primary abiotic constraint for bean cultivation in semi-arid regions, drought stress significantly impacts both the yield and quality of beans. Foliar application of nanofertilizer has been shown to effectively improve crop yield and nutritional quality while mitigating environmental pollution associated with fertilizer runoff. In this study, we conducted a semi-field study using magnetite nanoparticles (Fe3O4NPs) to evaluate its effects on the growth, yield, nutrient quality, photosynthetic parameters, and physiological traits in kidney bean (Phaseolus vulgaris L.) subjected to drought stress and compared with ferrous sulfate (FeSO4; ionic Fe). Our findings revealed that moderate drought stress (50 % field water capacity) severely impaired growth and photosynthetic activity in kidney bean in untreated control plants. Notably, application of 500-1000 mg Fe L-1 as Fe3O4NPs, in contrast to 1000 mg Fe L-1 of ionic Fe, resulted in increased yield (29-72 %), grain quality (protein 7-17 % and iron 10-45 %), and photosynthetic apparatus (245-259 % for Chla; 203-260 % for Chlb), under drough condition. Furthermore, foliar applications of Fe3O4NPs promoted drought tolerance by increasing relative water content and proline levels, vis-à-vis reducing membrane lipid peroxidation and electrolyte leakage. It is concluded that Fe3O4NPs at 500-1000 mg L-1 could significantly promote growth, quality, and physiological attributes in kidney bean under moderate drought stress, underscoring the potential advantages of using nano‑iron over ionic iron fertilizers for improved agriculture production.

Integrated metabolomics and transcriptomics reveal the role of calcium sugar alcohol in the regulation of phenolic acid biosynthesis in Torreya grandis nuts

BACKGROUND

Torreya grandis, a prominent tree species of the autochthonous subtropical region of China, possesses a drupe-like fruit containing a nut that is rich in nutrients and bioactive compounds. However, the effect of calcium (Ca2+) sugar alcohol (CSA), a newly developed chelated Ca2+-fertilizer, on the secondary metabolism of phenolics in T. grandis nuts is largely unknown, for which transcriptomic and metabolomic analysis was carried out.

RESULTS

Transcriptome sequencing detected 47,064 transcripts, and several phenolic acid biosynthesis pathway-related genes were identified. Correlation analysis showed that the four transcription factors, TgWRKY1, TgAP2-1, TgAP2-3, and TgAP2-4, were positively associated with the accumulation of phenolic acids. Furthermore, the binding of TgAP2-1 to the TgHCT promoter was confirmed using yeast one hybrid and dual-luciferase assays. Furthermore, the expression of TgHCT in Nicotiana enhanced the total flavonoid content.

CONCLUSIONS

Our results indicated that a new regulatory module, Ca2+-AP2-HCT, involved in the regulation of phenolic acid biosynthesis was revealed, expanding the understanding of the role of Ca2+ fertilizers in plant secondary metabolism.

Oryza glumaepatula and calcium oxide nanoparticles enhanced Cr stress tolerance by maintaining antioxidant defense, chlorophyll and gene expression levels in rice

Chromium (Cr), a potent heavy metal, threatens rice cultivation due to its escalating presence in soil from human activities. Wild rice contains useful genes for phytoremediation; however, it is difficult to use directly for metal mitigation. Here, a single segment substitution line (SSSL), SG001, was developed by crossing O. glumaepatula and Huajingxian74 (HJX) to evaluate the survival ability of plants against Cr. Further, we explored the potential effect of calcium oxide nanoparticles (CaO-NPs) (50 μM) to minimize the toxic effect of Cr (100 μM) in rice cultivars, SG001 and HJX. The findings of this study indicated that Cr toxicity led to increased oxidative stress. This was shown by higher levels of hydrogen peroxide (H2O2), which was increased by 104% in SG001 and 177% in HJX, and malondialdehyde (MDA) increased by 79% in SG001 and 135% in HJX. Furthermore, it also depicted that Cr toxicity considerably declined shoot and root length, shoot and root fresh weight by 30%, 27%, 25%, and 20% in SG001 and 44%, 51%, 42%, and 45% in HJX, respectively. This mitigation was evidenced by decreased Cr contents, increased calcium (Ca) levels in SG001, and the maintenance of chlorophyll, antioxidant defense, and gene expression levels. Moreover, there was a notable reduction in MDA and H2O2, while the defense mechanisms of key antioxidants, including ascorbate peroxidase, superoxide dismutase, glutathione, catalase, and peroxidase were upregulated, along with an increase in soluble protein contents in both rice cultivars after applying CaO-NPs. CaO-NPs effectively restored cellular and subcellular structural integrity and growth in both lines, which had been seriously disrupted by Cr toxicity. Overall, our findings suggest that SG001, in combination with CaO-NPs, could serve as an effective strategy to mitigate Cr toxicity in plants.

Nanoparticle-plant interactions: Physico-chemical characteristics, application strategies, and transmission electron microscopy-based ultrastructural insights, with a focus on stereological research

Ensuring global food security is pressing among challenges like population growth, climate change, soil degradation, and diminishing resources. Meeting the rising food demand while reducing agriculture's environmental impact requires innovative solutions. Nanotechnology, with its potential to revolutionize agriculture, offers novel approaches to these challenges. However, potential risks and regulatory aspects of nanoparticle (NP) utilization in agriculture must be considered to maximize their benefits for human health and the environment. Understanding NP-plant cell interactions is crucial for assessing risks of NP exposure and developing strategies to control NP uptake by treated plants. Insights into NP uptake mechanisms, distribution patterns, subcellular accumulation, and induced alterations in cellular architecture can be effectively drawn using transmission electron microscopy (TEM). TEM allows direct visualization of NPs within plant tissues/cells and their influence on organelles and subcellular structures at high resolution. Moreover, integrating TEM with stereological principles, which has not been previously utilized in NP-plant cell interaction assessments, provides a novel and quantitative framework to assess these interactions. Design-based stereology enhances TEM capability by enabling precise and unbiased quantification of three-dimensional structures from two-dimensional images. This combined approach offers comprehensive data on NP distribution, accumulation, and effects on cellular morphology, providing deeper insights into NP impact on plant physiology and health. This report highlights the efficient use of TEM, enhanced by stereology, in investigating diverse NP-plant tissue/cell interactions. This methodology facilitates detailed visualization of NPs and offers robust quantitative analysis, advancing our understanding of NP behavior in plant systems and their potential implications for agricultural sustainability.

Insights in to iron-based nanoparticles (hematite and magnetite) improving the maize growth (Zea mays L.) and iron nutrition with low environmental impacts

The possible potential application of Fe-NPs on Fe nutrition, heavy metals uptake and soil microbial community needs to be investigated. In the current research, a pot experiment was used to examine the implications of Fe-NPs (α-Fe2O3 and Fe3O4) on maize growth, Fe uptake and transportation, soil microbial community, and environmental risk. Fe3O4, α-Fe2O3, FeSO4 at a rate of 800 mg Fe kg-1 were applied in soils with four replications under a completely randomized design for a period of 60 days. Results showed that Fe uptake by maize roots were increased by 107-132% than control, with obvious variations across different treatments (Fe3O4> α-Fe2O3> FeSO4> control). Similarly, plant height, leaf surface area, and biomass were increased by 40-64%, 52-91% and 38-109% respectively, with lower values by FeSO4 application. The elevated level of chlorophyll contents and carotenoids and significant effects with control on antioxidant enzymes activities (i.e., catalase, and superoxide dismutase) suggested that application of Fe-NPs improved overall biochemical processes. The differential expression of important Fe transporters (i.e., ZmYS1 and ZmFER1) as compared to control indicated the plant strategic response for efficient uptake and distribution of Fe. Importantly, Fe-NPs reduced the heavy metals uptake (i.e., chromium, cadmium, arsenic, nickel, copper) by complex formation, and showed no toxicity to the soil microbial community. In summary, the application of Fe-NPs can be a promising approach for improving crop productivity and Fe nutrition without negatively affecting soil microbial community, and fostering sustainable agricultural production.

Ferric Oxide Nanomaterials and Plant-Rhizobacteria Symbionts Cogenerate Iron Plaque for Removing Highly Chlorinated Contaminants in Dryland Soils

Rhizosphere iron plaques derived from Fe-based nanomaterials (NMs) are a promising tool for sustainable agriculture. However, the requirement for flooded conditions to generate iron plaque limits the scope of the NM application. In this study, we achieved in situ Fenton oxidation of a highly chlorinated persistent organic pollutant (2,2',4,5,5'-pentachlorobiphenyl, PCB101) through iron plaque mediated by the interaction between α-Fe2O3 NMs and plant-rhizobacteria symbionts under dryland conditions. Mechanistically, the coexistence of α-Fe2O3 NMs and Pseudomonas chlororaphis JD37 stimulated alfalfa roots to secrete acidic and reductive agents as well as H2O2, which together mediated the rhizosphere Fenton reaction and converted α-Fe2O3 NMs into iron plaque rich in Fe(II)-silicate. Further verifications reproduced the Fenton reaction in vitro using α-Fe2O3 NMs and rhizosphere compounds, confirming the critical role of •OH in the oxidative degradation of PCB101. Significant reductions in PCB101 content by 18.6%, 42.9%, and 23.2% were respectively found in stem, leaf, and soil after a 120-d treatment, proving the effectiveness of this NMs-plant-rhizobacteria technique for simultaneously safe crop production and soil remediation. These findings can help expand the potential applications of nanobio interaction and its mediated iron plaque generation for both agricultural practice and soil remediation.

Effects of foliar iron oxide nanoparticles (Fe3O4) application on photosynthetic parameters, distribution of mineral elements, magnetic behaviour, and photosynthetic genes in tomato (Solanum lycopersicum var. cerasiforme) plants

This study aims to examine the effect of foliar magnetic iron oxide (Fe3O4) nanoparticles (IONP) application on the physiology, photosynthetic parameters, magnetic character, and mineral element distribution of cherry tomatoes (Solanum lycopersicum var. cerasiforme). The IONP suspension (500 mg L-1) was sprayed once (S1), twice (S2), thrice (S3), and four times (S4) a week on seedlings. Upon 21 days of the treatments, photosynthetic parameters (chlorophyll, carotenoids, photosynthetic yield, electron transport rate) were elucidated. Inductively-coupled plasma-optical emission spectrometer (ICP-OES) and vibrating sample magnetometer (VSM) were used to determine the mineral elements and abundance of magnetic power in the seedlings. In addition, the RT-qPCR method was performed to quantify the expressions of photosystem-related (PsaC, PsbP6, and PsbQ) and ferritin-coding (Fer-1 and Fer-2) genes. Results revealed that the physiological and photosynthetic indices were improved upon S1 treatment. The optimal dosage of IONP spraying enhances chlorophyll, carotenoid, electron transport rate (ETR), and effective photochemical quantum yield of photosystem II (Y(II)) but substantially diminishes non-photochemical quenching (NPQ). However, frequent IONP applications (S2, S3, and S4) caused growth retardation and suppressed the photosynthetic parameters, suggesting a toxic effect of IONP in recurrent treatments. Fer-1 and Fer-2 expressions were strikingly increased by IONP applications, suggesting an attempt to neutralize the excess amount of Fe ions by ferritin. Nevertheless, frequent IONP treatment fluctuated the mineral distribution and caused growth inhibition. Although low-repeat foliar applications of IONP (S1 in this study) may help improve plant growth, consecutive applications (S2, S3, and S4) should be avoided.

Inulin-Coated ZnO Nanoparticles: A Correlation between Preparation and Properties for Biostimulation Purposes

Within the framework of plant biostimulation, a pivotal role is played by the achievement of low-cost, easily prepared nanoparticles for priming purposes. Therefore, in this report, two different synthetic strategies are described to engineer zinc oxide nanoparticles with an inulin coating. In both protocols, i.e., two-step and gel-like one-pot protocols, nanoparticles with a highly pure ZnO kernel are obtained when the reaction is carried out at T ≥ 40 °C, as ascertained by XRD and ATR/FTIR studies. However, a uniformly dispersed, highly homogeneous coating is achieved primarily when different temperatures, i.e., 60 °C and 40 °C, are employed in the two phases of the step-wise synthesis. In addition, a different binding mechanism, i.e., complexation, occurs in this case. When the gel-like process is employed, a high degree of coverage by the fructan is attained, leading to micrometric coated aggregates of nanometric particles, as revealed by SEM investigations. All NPs from the two-step synthesis feature electronic bandgaps in the 3.25-3.30 eV range in line with previous studies, whereas the extensive coating causes a remarkable 0.4 eV decrease in the bandgap. Overall, the global analysis of the investigations indicates that the samples synthesized at 60 °C and 40 °C are the best suited for biostimulation. Proof-of-principle assays upon Vicia faba seed priming with Zn5 and Zn5@inu indicated an effective growth stimulation of seedlings at doses of 100 mgKg-1, with concomitant Zn accumulation in the leaves.