Plant abiotic stress leads to accumulation of reactive oxygen species (ROS) and a consequent decrease in photosynthetic performance. We demonstrate that a plant nanobionics approach of localizing negatively charged, sub-11 nm, spherical cerium oxide nanoparticles (nanoceria) inside chloroplasts in vivo augments ROS scavenging and photosynthesis of Arabidopsis thaliana plants under excess light (2000 μmol m s, 1.5 h), heat (35 °C, 2.5 h), and dark chilling (4 °C, 5 days). Poly(acrylic acid) nanoceria (PNC) with a hydrodynamic diameter (10.3 nm)-lower than the maximum plant cell wall porosity-and negative ζ-potential (-16.9 mV) exhibit significantly higher colocalization (46%) with chloroplasts in leaf mesophyll cells than aminated nanoceria (ANC) (27%) of similar size (12.6 nm) but positive charge (9.7 mV). Nanoceria are transported into chloroplasts via nonendocytic pathways, influenced by the electrochemical gradient of the plasma membrane potential. PNC with a low Ce/Ce ratio (35.0%) reduce leaf ROS levels by 52%, including hydrogen peroxide, superoxide anion, and hydroxyl radicals. For the latter ROS, there is no known plant enzyme scavenger. Plants embedded with these PNC that were exposed to abiotic stress exhibit an increase up to 19% in quantum yield of photosystem II, 67% in carbon assimilation rates, and 61% in Rubisco carboxylation rates relative to plants without nanoparticles. In contrast, PNC with high Ce/Ce ratio (60.8%) increase overall leaf ROS levels and do not protect photosynthesis from oxidative damage during abiotic stress. This study demonstrates that anionic, spherical, sub-11 nm PNC with low Ce/Ce ratio can act as a tool to study the impact of oxidative stress on plant photosynthesis and to protect plants from abiotic stress.

The regulation of engineered nanoparticles requires a widely agreed definition of such particles. Nanoparticles are routinely defined as particles with sizes between about 1 and 100 nm that show properties that are not found in bulk samples of the same material. Here we argue that evidence for novel size-dependent properties alone, rather than particle size, should be the primary criterion in any definition of nanoparticles when making decisions about their regulation for environmental, health and safety reasons. We review the size-dependent properties of a variety of inorganic nanoparticles and find that particles larger than about 30 nm do not in general show properties that would require regulatory scrutiny beyond that required for their bulk counterparts.

Iron deficiency anaemia is a major challenge among consumers in developing countries. Given the deficiency of iron in the diet, there is an urgent need to devise a strategy for providing the required iron in the daily diet to counter the iron deficiency anaemia. We propose that iron biofortification of wheat (Triticum aestivum L.) through seed priming would be an innovative strategy to address this issue. This investigation attempts to find the interaction of iron oxide nanoparticles on germination, growth parameters and accumulation of grain iron in two contrasting wheat genotypes WL711 (low-iron genotype) and IITR26 (high-iron genotype). Wheat seeds were primed with different concentrations of iron oxide nanoparticles in the range of 25-600 ppm, resulting in differential accumulation of grain iron contents. We observed a pronounced increase in germination percentage and shoot length at 400 and 200 ppm treatment concentrations in IITR26 and WL711 genotypes, respectively. Intriguingly, the treatment concentration of 25 ppm demonstrated higher accumulation with a significant increase in grain iron contents to 45.7% in IITR26 and 26.8% in WL711 genotypes, respectively. Seed priming represents an innovative and user-friendly approach for wheat biofortification which triggers iron acquisition and accumulation in grains.

Understanding plant interactions with nanoparticles is of increasing importance for assessing their toxicity and trophic transport. The primary objective of this study was to assess uptake, biodistribution and toxicity associated with exposure of tobacco plants (Nicotiana xanthi) to gold nanoparticles (AuNPs). We employed synchrotron-based X-ray microanalysis with X-ray absorption near-edge microspectroscopy and high resolution electron microscopy to localize AuNPs within plants. Results from these experiments reveal that AuNPs entered plants through the roots and moved into the vasculature. Aggregate bodies were also detected within root cell cytoplasm. Furthermore, AuNP uptake was size selective as 3.5 nm AuNP spheres were detected in plants but 18 nm AuNPs remained agglomerated on the root outer surfaces. Finally, leaf necrosis was observed after 14 days of exposure to 3.5 nm AuNPs. Overall, results of this work show the potential for AuNPs to enter plants through size-dependent mechanisms, translocate to cells and tissues and cause biotoxicity.

Effects of CeO NPs (200 mg.L) on rice (Oryza sativa L.) alone or co-exposure with cadmium (Cd) and salt (sodium chloride, NaCl) were investigated in hydroponic systems for two weeks. Physiological results show that rice biomass was significantly inhibited when NaCl or CdCl added alone or in co-exposure treatment. CeO NPs significantly relieve the chlorophyll damage under CdCl environmental stress. The presence of CeO NPs alleviated both stressors induced damages to rice as indicated by the reduced proline level. Additionally, CeO NPs triggered the antioxidant defense systems to counteract the oxidative stress caused by NaCl and CdCl. The level of 8-OHdG, one of the most important indicators for genotoxicity, in rice suggest that the presence of CeO NPs reduced the DNA damage in NaCl treated rice. Elemental analysis indicated that co-exposure to NaCl and CdCl slightly decreased the Cd content as compared to the one in the CdCl alone treatment, and this co-exposure also significantly reduced the Na content when comparing with the NaCl alone treatment. Taken together, our findings suggest that CeO NPs could alleviate the CdCl and NaCl stresses, but could not completely change the phenotype of both contaminants treated rice.Copyright © 2019 Elsevier Ltd. All rights reserved.

Treated wastewater is reclaimed to irrigate crops in a growing number of arid and semi-arid areas. In order to study the impacts of metallic nanoparticles (NPs) present in treated wastewater on soil ecosystems, a soil micro ecosystem containing Arabidopsis thaliana plants, soil microorganisms, and Eisenia fetida earthworms was developed. The soil was irrigated with deionized water containing environmentally relevant concentrations of 70 mu g/L of TiO2 NPs; or 20 mu g/L of an Ag mixture, which included 90% (w/w) Ag2S NPs, 7.5% (w/w) Ag-0 NPs, and 2.5% (w/w) Ag+ to represent speciation of aged Ag NPs in treated wastewater; or a combination of the TiO2 NPs and the Ag mixture to reflect the frequent presence of both types of materials in treated wastewater. It was found that TiO2 NPs alone were not toxic to the soil micro-ecosystem. Irrigation water containing 20 mu g/L of the Ag mixture significantly reduced the soil microbial biomass, and inhibited the growth of plants and earthworms; however, a combination of 70 mu g/L of TiO2 and 20 mu g/L of Ag did not show toxic impact on organism growth compared to the Control of deionized water irrigation. Taken together, these results indicate the importance of investigating the effects of different nanomaterials in combination as they are introduced to the environment-with environmentally relevant concentrations and speciation-instead of only selecting a single NP type or residual ion. Moreover, the results of this study support the safe application of reclaimed water from wastewater treatment plants for use in agricultural lands in regard to limited concentrations of aged NPs (i.e., TiO2 and Ag) if present in combination.

Fundamental and quantitative understanding of the interactions between nanoparticles and plant leaves is crucial for advancing the field of nanoenabled agriculture. Herein, we systematically investigated and modeled how ζ potential (-52.3 mV to +36.6 mV) and hydrodynamic size (1.7-18 nm) of hydrophilic nanoparticles influence delivery efficiency and pathways to specific leaf cells and organelles. We studied interactions of nanoparticles of agricultural interest including carbon dots (CDs, 0.5 and 5 mg/mL), cerium oxide (CeO, 0.5 mg/mL), and silica (SiO, 0.5 mg/mL) nanoparticles with leaves of two major crop species having contrasting leaf anatomies: cotton (dicotyledon) and maize (monocotyledon). Biocompatible CDs allowed real-time tracking of nanoparticle translocation and distribution by confocal fluorescence microscopy at high spatial (∼200 nm) and temporal (2-5 min) resolution. Nanoparticle formulations with surfactants (Silwet L-77) that reduced surface tension to 22 mN/m were found to be crucial for enabling rapid uptake (<10 min) of nanoparticles through the leaf stomata and cuticle pathways. Nanoparticle-leaf interaction (NLI) empirical models based on hydrodynamic size and ζ potential indicate that hydrophilic nanoparticles with <20 and 11 nm for cotton and maize, respectively, and positive charge (>15 mV), exhibit the highest foliar delivery efficiencies into guard cells (100%), extracellular space (90.3%), and chloroplasts (55.8%). Systematic assessments of nanoparticle-plant interactions would lead to the development of NLI models that predict the translocation and distribution of nanomaterials in plants based on their chemical and physical properties.

Nanoenabled foliar-applied agrochemicals can potentially be safer and more efficient than conventional products. However, limited understanding about how nanoparticle properties influence their interactions with plant leaves, uptake, translocation through the mesophyll to the vasculature, and transport to the rest of the plant prevents rational design. This study used a combination of Au quantification and spatial analysis to investigate how size (3, 10, or 50 nm) and coating chemistry (PVP versus citrate) of gold nanoparticles (AuNPs) influence these processes. Following wheat foliar exposure to AuNPs suspensions (∼280 ng per plant), adhesion on the leaf surface was increased for smaller sizes, and PVP-AuNPs compared to citrate-AuNPs. After 2 weeks, there was incomplete uptake of citrate-AuNPs with some AuNPs remaining on the outside of the cuticle layer. However, the fraction of citrate-AuNPs that had entered the leaf was translocated efficiently to the plant vasculature. In contrast, for similar sizes, virtually all of the PVP-AuNPs crossed the cuticle layer after 2 weeks, but its transport through the mesophyll cells was lower. As a consequence of PVP-AuNP accumulation in the leaf mesophyll, wheat photosynthesis was impaired. Regardless of their coating and sizes, the majority of the transported AuNPs accumulated in younger shoots (10-30%) and in roots (10-25%), and 5-15% of the NPs <50 nm were exuded into the rhizosphere soil. A greater fraction of larger sizes AuNPs (presenting lower ζ potentials) was transported to the roots. The key hypotheses about the NPs physical-chemical and plant physiology parameters that may matter to predict leaf-to-rhizosphere transport are also discussed.

Current agricultural practices, developed during the green revolution, are becoming unsustainable, especially in the face of climate change and growing populations. Nanotechnology will be an important driver for the impending agri-tech revolution that promises a more sustainable, efficient and resilient agricultural system, while promoting food security. Here, we present the most promising new opportunities and approaches for the application of nanotechnology to improve the use efficiency of necessary inputs (light, water, soil) for crop agriculture, and for better managing biotic and abiotic stress. Potential development and implementation barriers are discussed, emphasizing the need for a systems approach to designing proposed nanotechnologies.

Magnetite nanoparticles use for the remediation of toxic metal ions. Therefore, the scope of green synthesis of magnetite nanoparticles from Hevea bark extract, and application of these particles for the environmental remediation of Cd and Na tested. Mixing of 10.0 mL each bark extract (1.0 g in 25.0 mL HO) and iron solution (10.0 mM FeCl and 5.0 mM FeCl) resulted formation of semicrystalline magnetite nanoparticles having magnetic saturation at 10 G. The particles characterized with the help of scanning electron microscopy, energy dispersive spectroscopy, Uv-vis spectroscopy, vibrating sample magnetometry, powder X-Ray diffraction, Fourier-transform infrared spectroscopy, and differential thermal analysis coupled with thermogravimetry. The phytochemicals responsible for priming and coating of nanoparticle were phenolics, especially benzoic acid derivatives. Adsorption of metal ions to nanoparticles followed pseudo-second-order model. Maximum Cd and Na adsorption capacity were 37.03 and 3.95 mg g respectively. The difference in Cd and Na adsorption capacity was the result of multilayer and monolayer adsorption processes respectively. Highest metal ion adsorption occurred at temperature 10.0-20.0 °C and pH 6.0. Metal adsorption property of the nanoparticles decreased the accumulation of Cd and Na in rice plants. The plant growth promotion effects of nanoparticles explained regarding biomass, osmolyte content, and oxidative stress tolerance. Therefore, the nanoparticles produced in the study can use as a magnetically separable nano sorbent of metal ions as well as ameliorant of metal stress in rice.Copyright © 2019 Elsevier B.V. All rights reserved.

Silicon (Si) alleviates cadmium (Cd) toxicity in rice (Oryza sativa). However, the chemical mechanisms at the single-cell level are poorly understood. Here, a suspension of rice cells exposed to Cd and/or Si treatments was investigated using a combination of plant cell nutritional, molecular biological, and physical techniques including in situ noninvasive microtest technology (NMT), polymerase chain reaction (PCR), inductively coupled plasma mass spectroscopy (ICP-MS), and atomic force microscopy (AFM) in Kelvin probe mode (KPFM). We found that Si-accumulating cells had a significantly reduced net Cd(2+) influx, compared with that in Si-limited cells. PCR analyses of the expression levels of Cd and Si transporters in rice cells showed that, when the Si concentration in the medium was increased, expression of the Si transporter gene Low silicon rice 1 (Lsi1) was up-regulated, whereas expression of the gene encoding the transporter involved in the transport of Cd, Natural resistance-associated macrophage protein 5 (Nramp5), was down-regulated. ICP-MS results revealed that 64% of the total Si in the cell walls was bound to hemicellulose constituents following the fractionation of the cell walls, and consequently inhibited Cd uptake. Furthermore, AFM in KPFM demonstrated that the heterogeneity of the wall surface potential was higher in cells cultured in the presence of Si than in those cultured in its absence, and was homogenized after the addition of Cd. These results suggest that a hemicellulose-bound form of Si with net negative charges is responsible for inhibition of Cd uptake in rice cells by a mechanism of [Si-hemicellulose matrix]Cd complexation and subsequent co-deposition. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

TiO nano particles (NPs) are one of the most produced nanoparticles in the world which are increasingly being released in to the soil. Soils are exposed to various level of concentration of TiO NPs, which has raised concern over the adverse influence on soil microbial community, in turn on ecosystem functions. Although, increasing number of studies on ecotoxicological effect of TiO NPs are coming up recently, however, a common conscience has yet to be reached regarding the impact of TiO NPs on soil microbial community and processes. Moreover, very few studies have targeted soil enzymes which are being considered as sensitive indicator of soil health. Therefore, the present study has been carried out to estimate the ecotoxicological effect of various doses of TiO NPs (5, 10, 20, 40, 80, 100 mg kg soil) on different soil enzymes and microbial community structure. Results revealed that soil enzyme activities and microbial biomass had a uniform trend where the value increased up to the dose of 20 mg TiO NPs kg soil and there onwards reduced drastically up to 100 mg TiO NPs kg soil dose. On the contrary, soil respiration and metabolic quotient kept increasing up to 100 mg TiO NPs kg soil dose indicating sub-lethal stress on microbial community. Nevertheless, the structure of microbial community had slightly different trend where the biomass of total phospho lipid fatty acid (PLFA), Gram positive, Gram negative bacteria, fungi, actinomyctetes and anaerobes were found to be increased up to dose of 80 mg TiO NPs kg soil, but, significantly declined at 100 mg TiO NPs kg soil dose. Furthermore, temperature effect on TiO NPs toxicity had exhibited a less negative impact at 40 °C rather than at 25 °C. In addition alteration index (AI3), an integrated indicator of C, N, P cycling of soils as well as a well-documented indicator of soil pollution, has been found to be regulated by soil respiration, clay content, anaerobe and eukaryote for AI3-Acid Phos. and by fungi to bacteria ratio, soil respiration, microbial biomass and Gram positive bacteria for AI3-Alk. Phos. Overall, the study provided valuable information regarding ecotoxicological impact of environmentally relevant concentrations of TiO NPs in clay loam soils as well as improved our perception regarding the impact of NPs on soil functioning.

Although it was recently determined that silicon can alleviate cadmium (Cd) toxicity in rice, the effects of silicon properties and the molecular mechanisms are still unclear. Here, the effect of silica nanoparticles (SiNPs) on Cd toxicity in rice was examined using cells cultured in suspension in the presence or absence of SiNPs (19 nm, 48 nm and 202 nm). The results showed that the presence of SiNPs substantially enhanced the proportion of live cells to 95.4%, 78.6% and 66.2%, respectively, suggesting that the extent of alleviation of Cd toxicity decreased gradually with size of SiNPs. The morphological results showed that dramatic damage and severe structural changes in the organelle integrity of cells occurred in the absence of SiNPs, whereas the cells exposed to the SiNPs remained nearly intact even in the presence of high concentrations of Cd. Furthermore, the SiNPs accumulated on the surface of the rice cells. Using inductively coupled plasma mass spectroscopy, Cd accumulated preferentially in plant cells with cell walls. In addition, noninvasive microtest technology showed that the average Cd influx in those treated with SiNPs (19 nm, 48 nm and 202 nm) decreased by 15.7-, 11.1- and 4.6-fold, respectively. The gene expression of Cd uptake and transport (OsLCT1 and OsNramp5) was inhibited by SiNPs, but the gene expression of Cd transport into vacuole (OsHMA3) and Si uptake (OsLsi1) was enhanced by the SiNPs. These results indicate that the presence of SiNPs increased at least 1.87-fold the Si uptake capacity and inhibited the Cd uptake capacity, which together resulted in the alleviation of the toxicity of Cd in rice. This study provided a molecular-scale insight into the understanding of the SiNPs-induced alleviation of the toxicity of Cd in rice.Copyright © 2017. Published by Elsevier Ltd.

By 2050, the global population is projected to reach 9 billion, underscoring the imperative for innovative solutions to increase grain yield and enhance food security. Nanotechnology has emerged as a powerful tool, providing unique solutions to this challenge. Nanoparticles (NPs) can improve plant growth and nutrition under normal conditions through their high surface-to-volume ratio and unique physical and chemical properties. Moreover, they can be used to monitor crop health status and augment plant resilience against abiotic stresses (such as salinity, drought, heavy metals, and extreme temperatures) that endanger global agriculture. Application of NPs can enhance stress tolerance mechanisms in plants, minimizing potential yield losses and underscoring the potential of NPs to raise crop yield and quality. This review highlights the need for a comprehensive exploration of the environmental implications and safety of nanomaterials and provides valuable guidelines for researchers, policymakers, and agricultural practitioners. With thoughtful stewardship, nanotechnology holds immense promise in shaping environmentally sustainable agriculture amid escalating environmental challenges.

Rapid developments in nanotechnology have led to the increasing use of nanoparticles (NPs) in the agricultural sector. For possible interactions between NPs and crops under flooding stress to be investigated, the molecular mechanisms in soybeans affected by exposure to various sizes of AlO NPs were analyzed using a proteomic technique. In plants exposed to 30-60 nm AlO NPs, the length of the root including hypocotyl was increased, and proteins related to glycolysis were suppressed. Exposure to 30-60 nm AlO NPs mediated the scavenging activity of cells by regulating the ascorbate/glutathione pathway. Hierarchical clustering analysis indicated that ribosomal proteins were also increased upon exposure to flooding-stressed plants with 30-60 nm AlO NPs. Mitochondrion was the target organelle of AlO NPs under flooding-stress conditions. Mitochondrial proteomic analysis revealed that the abundance of voltage-dependent anion channel protein was increased upon exposure to flooding-stressed soybeans with 135 nm AlO NPs, indicating the permeability of the mitochondrial membrane was increased. Furthermore, isocitrate dehydrogenase was increased upon exposure of plants to 5 nm AlO NPs under flooding conditions. These results suggest that AlO NPs of various sizes affect mitochondrial proteins under flooding stress by regulating membrane permeability and tricarboxylic acid cycle activity.