Carbon Nanotubes Filled with Different Ferromagnetic Alloys Affect the Growth and Development of Rice Seedlings by Changing the C:N Ratio and Plant Hormones Concentrations - Fig 5

<p>Transmission electron micrographs of untreated rice roots (A), rice roots treated with MWCNTs (B), Fe-CNTs (C), FeCo-CNTs (D), EDS spectra of FeCo-CNTs in rice roots (E). CNTs are circled in images, cw: cell wall.</p

Engineering Climate-Resilient Rice Using a Nanobiostimulant-Based “Stress Training” Strategy

Under a changing climate, cultivating climate-resilient crops will be critical to maintaining food security. Here, we propose the application of reactive oxygen species (ROS)-generating nanoparticles as nanobiostimulants to trigger stress/immune responses and subsequently increase the stress resilience of plants. We established three regimens of silver nanoparticles (AgNPs)-based “stress training”: seed training (ST), leaf training (LT), and combined seed and leaf training (SLT). Trained rice seedlings were then exposed to either rice blast fungus (Magnaporthe oryzae) or chilling stress (10 °C). The results show that all “stress training” regimes, particularly SLT, significantly enhanced the resistance of rice against the fungal pathogen (lesion size reduced by 82% relative to untrained control). SLT also significantly enhanced rice tolerance to cold stress. The mechanisms for the enhanced resilience were investigated with metabolomics and transcriptomics, which show that “stress training” induced considerable metabolic and transcriptional reprogramming in rice leaves. AgNPs boosted ROS-activated stress signaling pathways by oxidative post-translational modifications of stress-related kinases, hormones, and transcriptional factors (TFs). These signaling pathways subsequently modulated the expression of defense genes, including specialized metabolites (SMs) biosynthesis genes, cell membrane lipid metabolism genes, and pathogen–plant interaction genes. Importantly, results showed that the “stress memory” can be transferred transgenerationally, conferring offspring seeds with improved seed germination and seedling vigor. This may provide an epigenetic breeding strategy to fortify stress resilience of crops. This nanobiostimulant-based stress training strategy will increase yield vigor against a changing climate and will contribute to sustainable agriculture by reducing agrochemical use

C: N ratio in rice roots and shoots after treatments with three different carbon nanotubes.

<p>C: N ratio in rice roots and shoots after treatments with three different carbon nanotubes.</p

Microplastic and Nanoplastic Interactions with Plant Species: Trends, Meta-Analysis, and Perspectives

The ubiquitous presence of nanoplastics (NPx) and microplastics (MPx) in the environment has been demonstrated, and as such, the exposure scenarios, mechanisms of plant response, and ultimate risk must be determined. Here, we performed a meta-analysis of the most recent literature investigating the effect of MPx/NPx on plant species under laboratory and field conditions so as to evaluate the current state of knowledge. Effects of MPx/NPx exposure in plants vary as a function of plant species, and interestingly, nonsignificant responses are reported in staple crops. We found that NPx (<100 nm) more negatively affected plant development parameters, photosynthetic pigments, and biochemical indicators than did MPx (>100 nm). Surprisingly, NPx exposure exhibited negligible effects on germination rate, although root morphology was negatively affected. Alternatively, MPx negatively affected (14%) germination and generally exhibited nonsignificant effects on root morphology. The effect of MPx/NPx on plant health decreases with increasing exposure time. No specific trends were evident for the production of biochemical enzymes as related to MPx/NPx concentration or size. Furthermore, we provided a framework for additional investigative work to address the knowledge gaps and to enable accurate assessment of the fate and risk of these materials to environmental and human health

Nanoenabled Enhancement of Plant Tolerance to Heat and Drought Stress on Molecular Response

Global warming has posed significant pressure on agricultural productivity. The resulting abiotic stresses from high temperatures and drought have become serious threats to plants and subsequent global food security. Applying nanomaterials in agriculture can balance the plant’s oxidant level and can also regulate phytohormone levels and thus maintain normal plant growth under heat and drought stresses. Nanomaterials can activate and regulate specific stress-related genes, which in turn increase the activity of heat shock protein and aquaporin to enable plants’ resistance against abiotic stresses. This review aims to provide a current understanding of nanotechnology-enhanced plant tolerance to heat and drought stress. Molecular mechanisms are explored to see how nanomaterials can alleviate abiotic stresses on plants. In comparison with organic molecules, nanomaterials offer the advantages of targeted transportation and slow release. These advantages help the nanomaterials in mitigating drought and heat stress in plants

(A) Ce contents in roots (A) and leaves (B) of lettuce plants.

<p>Error bars stand for standard errors. Bar with the same letters show no statistically significant differences at p≤0.05. n = 8.</p

Fate and Phytotoxicity of CeO₂ Nanoparticles on Lettuce Cultured in the Potting Soil Environment

<div><p>Cerium oxide nanoparticles (CeO₂ NPs) have been shown to have significant interactions in plants. Previous study reported the specific-species phytotoxicity of CeO₂ NPs by lettuce (<i>Lactuca sativa</i>), but their physiological impacts and vivo biotransformation are not yet well understood, especially in relative realistic environment. Butterhead lettuce were germinated and grown in potting soil for 30 days cultivation with treatments of 0, 50, 100, 1000 mg CeO₂ NPs per kg soil. Results showed that lettuce in 100 mg·kg^-1 treated groups grew significantly faster than others, but significantly increased nitrate content. The lower concentrations treatment had no impact on plant growth, compared with the control. However, the higher concentration treatment significantly deterred plant growth and biomass production. The stress response of lettuce plants, such as Superoxide dismutase (SOD), Peroxidase (POD), Malondialdehyde(MDA) activity was disrupted by 1000 mg·kg^-1 CeO₂ NPs treatment. In addition, the presence of Ce (III) in the roots of butterhead lettuce explained the reason of CeO₂ NPs phytotoxicity. These findings demonstrate CeO₂ NPs modification of nutritional quality, antioxidant defense system, the possible transfer into the food chain and biotransformation in vivo.</p></div

NO_3^--N (A) and soluble sugar (B) contents content in the leaves Error bars stand for standard errors.

<p>Bar with this asterisk (*) symbol shows statistically significant differences at <i>p</i>≤0.05, n = 8.</p

Molybdenum Nanofertilizer Boosts Biological Nitrogen Fixation and Yield of Soybean through Delaying Nodule Senescence and Nutrition Enhancement

Soybean (Glycine max) is a crop of global significance and has low reliance on N fertilizers due to its biological nitrogen fixation (BNF) capacity, which harvests ambient N2 as a critical ecosystem service. BNF can be severely compromised by abiotic stresses. Enhancing BNF is increasingly important not only to alleviate global food insecurity but also to reduce the environmental impact of agriculture by decreasing chemical fertilizer inputs. However, this has proven challenging using current genetic modification or bacterial nodulation methods. Here, we demonstrate that a single application of a low dose (10 mg/kg) of molybdenum disulfide nanoparticles (MoS2 NPs) can enhance soybean BNF and grain yield by 30%, compared with conventional molybdate fertilizer. Unlike molybdate, MoS2 NPs can more sustainably release Mo, which then is effectively incorporated as a cofactor for the synthesis of nitrogenase and molybdenum-based enzymes that subsequently enhance BNF. Sulfur is also released sustainably and incorporated into biomolecule synthesis, particularly in thiol-containing antioxidants. The superior antioxidant enzyme activity of MoS2 NPs, together with the thiol compounds, protect the nodules from reactive oxygen species (ROS) damage, delay nodule aging, and maintain the BNF function for a longer term. The multifunctional nature of MoS2 NPs makes them a highly effective strategy to enhance plant tolerance to abiotic stresses. Given that the physicochemical properties of nanomaterials can be readily modulated, material performance (e.g., ROS capturing capacity) can be further enhanced by several synthesis strategies. This study thus demonstrates that nanotechnology can be an efficient and sustainable approach to enhancing BNF and crop yield under abiotic stress and combating global food insecurity