Engineered nanoparticles in plant growth: Phytotoxicity concerns and the strategies for their attenuation

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.

Regulation effect of seed priming on sowing rate of direct seeding of rice under salt stress

Direct seeding of rice (DSR) is a widely used method for its labor- and cost-saving advantages. However, the global intensification of soil salinization presents a significant challenge to food security. Increasing sowing rates is a common practice to enhance germination under salt stress, although it leads to higher seed costs. Recently, seed priming has emerged as an effective technique to improve seedling emergence under abiotic stress, but the regulation of seed priming treatment on the sowing rate of DSR under saline soil conditions has rarely been reported. Therefore, field experiments were conducted at two salinity levels of 1.5‰ (1.5 g kg-1) (T2) and 3.0‰ (3 g kg-1) (T3) and under one non-saline condition (0‰) (T1). The control (P1) consisted of non-primed seeds, while priming treatments included 160 mg L-¹ ascorbic acid (P2), γ-aminobutyric acid (P3), and 200 mg L-¹ zinc oxide nanoparticles (P4); three sowing rates were applied: 90 (S1), 150 (S2), and 240 seeds m-2 (S3). Our results demonstrated that under T1-T3, the germination rate, α-amylase activity, and soluble sugar and protein contents were significantly increased after priming treatments. The contents of reactive oxygen species (i.e., O2 - and H2O2) and malondialdehyde (MDA) were decreased, while the activities of enzymatic antioxidants (i.e., superoxide dismutase, peroxidase, and catalase) and the K+/Na+ ratio of rice were significantly increased after the above seed priming treatments. Under T1-T3, the grain yield increased by 13.39%-36.94% after priming treatments, primarily due to enhanced seed germination, which boosted panicle number per unit area. Among P2-P4 treatments, P4 treatment consistently resulted in the highest yield increase (26.96%-36.94%) compared to P1, outperforming P2 and P3 under T1-T3. Furthermore, under T1-T3, the grain yield with priming treatment at 90 seeds m-2 was equivalent to that obtained without priming treatment at 240 seeds m-2. The potential mechanisms by which priming treatments enhance rice salt tolerance include increased levels of osmoregulatory substances and elevated activities of antioxidant enzymes, which collectively support improved seed germination. Therefore, to optimize the economic benefits of DSR when the salt concentration is below 3‰, the sowing rate could be reduced to 90 seeds m-2 using ZnO-nanoparticle priming treatment.

Impact of graphene oxide disturbance on the structure and function of arbuscular mycorrhizal networks

With the widespread application of graphene oxide (GO), its potential toxicity has received increasing attention. The extraradical mycelium of arbuscular mycorrhizal fungi (AMF) can extend from the roots of one plant to those of another, forming complex common mycorrhizal networks (CMNs) for the transfer of nutrients and infochemicals. However, the impact of GO on the structure and transfer function of CMNs remains unknown. In this study, controlled compartments with designated donors and receptors were established to form CMNs after inoculation of Festuca arundinacea plants with Rhizophagus irregularis. GO was found to inhibit host plant growth and decrease AMF colonization, nitrogen and phosphorus uptake, and signal transmission capability in the recipient plants. Specifically, exposure to 5 % GO resulted in decreases of 27.5 % and 35.0 % in shoot and root weights, respectively, and a 38.1 % reduction in AMF colonization. The shoot nitrogen and phosphorus contents were reduced by 41.0 % and 32.3 %, respectively, and the root nitrogen and phosphorus contents were reduced by 12.4 % and 38.6 %, respectively, in response to 5 % GO. Additionally, the upregulation of key genes, such as aquaporin (Rir-AQP2), nitrogen transporter (GiNT), urease (GiURE), and phosphorus transporter (GintPT) in Rhizophagus irregularis was observed in the roots of the recipient plants under the GO treatments, with maximum increases of 192.7 %, 182.6 %, 162.1 %, and 125.8 %, respectively. The differential expressed genes (DEGs) were notably enriched in processes such as the spliceosome and endocytosis, the pentose phosphate pathway, glycolysis and secondary metabolism, and amino acid metabolism. These findings strongly indicate that GO has a significant effect on the structure and functionality of CMNs.

Carbon dot unravels accumulation of triterpenoid in Evolvulus alsinoides hairy roots culture by stimulating growth, redox reactions and ANN machine learning model prediction of metabolic stress response

Evolvulus alsinoides, a therapeutically valuable shrub can provide consistent supply of secondary metabolites (SM) with pharmaceutical significance. Nonetheless, because of its short life cycle, fresh plant material for research and medicinal diagnostics is severely scarce throughout the year. The effects of exogenous carbon quantum dot (CD) application on metabolic profiles, machine learning (ML) prediction of metabolic stress response, and SM yields in hairy root cultures of E. alsinoides were investigated and quantified. The range of the particle size distribution of the CDs was between 3 and 7 nm. The CDs EPR signal and spin trapping experiments demonstrated the formation of O2-•spin-adducts at (g = 2.0023). Carbon dot treatment increased the levels of hydrogen peroxide and malondialdehyde concentrations as well as increased antioxidant enzyme activity. CD treatments (6 μg mL-1) significantly enhanced the accumulation of squalene and stigmasterol (7 and 5-fold respectively). The multilayer perceptron (MLP) algorithm demonstrated remarkable prediction accuracy (MSE value = 1.99E-03 and R2 = 0.99939) in both the training and testing sets for modelling. Based on the prediction, the maximum oxidative stress index and enzymatic activities were highest in the medium supplemented with 10 μg mL-1 CDs. The outcome of this study indicated that, for the first time, using CD could serve as a novel elicitor for the production of valuable SM. MLP may also be used as a forward-thinking tool to optimize and predict SM with high pharmaceutical significance. This study would be a touchstone for understanding the use of ML and luminescent nanomaterials in the production and commercialization of important SM.

Ecotoxicity of doped zinc oxide nanoparticles: Perspectives on environmental safety

Studies on the ecotoxicity of doped zinc oxide nanoparticles (ZnO NPs) are recent, with the first publications starting in 2010. In this sense, this is the first study that comprehensively reviews the ecotoxicological effects of ZnO NPs doped with lanthanide elements to fill this literature gap. This research explores a multifaceted question at the intersection of nanotechnology, toxicology, and environmental science. Different types of dopants commonly used for ZnO doping were investigated in this review, focusing on the ecotoxicological effects of lanthanides as dopants. Bacteria were the main class of organisms used in ecotoxicological studies, since antimicrobial activity of these nanomaterials is extensively explored to combat the imminent problem of resistant bacteria, in addition to enabling the safe use of these nanomaterials for biomedical applications. Doping appears to exhibit greater efficacy when compared to undoped ZnO NPs in terms of antimicrobial effects; however, it cannot be said that it has no impact on non-target organisms. An extensive examination of the literature also establishes the importance and need to evaluate the effects of doped ZnO NPs on organisms from different environmental compartments in order to identify their potential impacts. We underscore the dearth of research information regarding the environmental toxicity/ecotoxicity of doped ZnO nanoparticles across various ecological levels, thereby limiting the extrapolation of findings to humans or other complex models. Therefore, we emphasize the urgency of a multi-parameter assessment for the development of sanitary and environmentally safe nanotechnologies.

Impact of nanopollution on plant growth, photosynthesis, toxicity, and metabolism in the agricultural sector: An updated review

Nanotechnology provides distinct benefits to numerous industrial and commercial fields, and has developed into a discipline of intense interest to researchers. Nanoparticles (NPs) have risen to prominence in modern agriculture due to their use in agrochemicals, nanofertilizers, and nanoremediation. However, their potential negative impacts on soil and water ecosystems, as well as plant growth and physiology, have caused concern for researchers and policymakers. Concerns have been expressed regarding the ecological consequences and toxicity effects associated with nanoparticles as a result of their increased production and usage. Moreover, the accumulation of nanoparticles in the environment poses a risk, not only because of the possibility of plant damage but also because nanoparticles may infiltrate the food chain. In this review, we have documented the beneficial and detrimental effects of NPs on seed germination, shoot and root growth, plant biomass, and nutrient assimilation. Nanoparticles exert toxic effects by inducing ROS generation and stimulating cytotoxic and genotoxic effects, thereby leading to cell death in several plant species. We have provided possible mechanisms by which nanoparticles induce toxicity in plants. In addition to the toxic effects of NPs, we highlighted the importance of nanomaterials in the agricultural sector. Thus, understanding the structure, size, and concentration of nanoparticles that will improve plant growth or induce plant cell death is essential. This updated review reveals the multifaceted connection between nanoparticles, soil and water pollution, and plant biology in the context of agriculture.