Interaction of hyperaccumulating plants with Zn and Cd nanoparticles

Co-application of TiO2 nanoparticles and hyperaccumulator Brassica juncea L. for effective Cd removal from soil: Assessing the feasibility of using nano-phytoremediation

Nano-phytoremediation is anticipated as a potential technology for the remediation of heavy metals from soil sites. This study evaluated the feasibility of using titanium dioxide nanoparticles (TiO2 NPs) at various concentrations (0, 100, 250, 500 mg/kg) along with a hyperaccumulator, Brassica juncea L., for effective removal of Cadmium (Cd) from the soil. Plants were grown for a whole life cycle in soil containing 10 mg/kg of Cd and spiked TiO2 NPs. We analyzed the plants for Cd tolerance, phytotoxicity, Cd removal, and translocation. Brassica plants displayed high Cd tolerance with a significant increase in plant growth, biomass, and photosynthetic activity in a concentration-dependent manner. Cd removal from the soil at TiO2 NPs concentrations of 0, 100, 250, and 500 mg/kg treatment was 32.46%, 11.62%, 17.55%, and 55.11%, respectively. The translocation factor for Cd was found to be 1.35, 0.96, 3.73, and 1.27 for 0, 100, 250, and 500 mg/kg concentrations. The results of this study indicate that TiO2 NPs applications in the soil can minimize Cd stress in plants and lead to its efficient removal from soil. Thus, the association of nanoparticles with the phytoremediation process can lead to good application prospects for the remediation of contaminated soil.

Nano-Biofertilizer Formulations for Agriculture: A Systematic Review on Recent Advances and Prospective Applications

In the twenty-first century, nanotechnology has emerged as a potentially game-changing innovation. Essential minerals are mostly unavailable in modern cropping systems without the application of synthetic fertilizers, which have a serious negative impact on the ecosystem. This review focuses on the coupling of nanoparticles with biofertilizers to function as nano-biofertilizers (NBFs), which may ensure world food security in the face of the rising population. The inoculation of plants with NBFs improves plant development and resistance to stress. Metallic nanoparticles as well as organic components comprising polysaccharide and chitosan may be encapsulated, utilizing microbe-based green synthesis to make NBFs, which circumvents the limitations of conventional chemical fertilizers. The application of NBFs is just getting started, and shows more promise than other approaches for changing conventional farming into high-tech "smart" farming. This study used bibliographic analysis using Web of Science to find relevant papers on "nano biofertilizers", "plants", and "agriculture". These subjects have received a lot of attention in the literature, as shown by the co-citation patterns of these publications. The novel use of nanotechnology in agriculture is explored in this research work, which makes use of the unique characteristics of nanoscale materials to address urgent concerns including nutrient delivery, crop protection, and sustainable farming methods. This study attempts to fill in some of the gaps in our knowledge by discussing the formulation, fabrication, and characterization of NBFs, as well as elucidating the mechanisms by which NBFs interact with plants and how this benefits the ability of the plant to withstand biotic and abiotic stress brought about by climate change. This review also addresses recent developments and future directions in farming using NBF formulations in the field.

Phytoremediation Competence of Composite Heavy-Metal-Contaminated Sediments by Intercropping Myriophyllum spicatum L. with Two Species of Plants

A variety of remediation approaches have been applied to reduce the harm and diffusion of heavy metals in aquatic sediments; however, phytoremediation in co-contaminated soils is still not clear. In order to explore the phytoremediation of sediments contaminated by Cu and Pb, two submerged plants with different characteristics, Vallisneria natans and Hydrilla verticillata, were interplanted with Myriophyllum spicatum. By simulating a submerged plant ecological environment, medium-scale-simulated ecological remediation experiments were carried out. The results showed that the two planting patterns were effective in repairing the sediments in the Cu and Pb contaminated sediments. The intercropping of Myriophyllum spicatum and Vallisneria natans can be used as the plant stabilizer of Cu because of the TF > 1 and BCF < 1, and the intercropping with Hydrilla verticillata can regulate the enrichment efficiency of Myriophyllum spicatum. The removal rates of Cu and Pb in sediments reached 26.1% and 68.4%, respectively, under the two planting patterns. The risk grade of the restored sediments was RI < 150, indicating a low risk.

Nanomaterials biotransformation: In planta mechanisms of action

Research on engineered nanomaterials (ENMs) exposure has continued to expand rapidly, with a focus on uncovering the underlying mechanisms. The EU largely limits the number and the type of organisms that can be used for experimental testing through the 3R normative. There are different routes through which ENMs can enter the soil-plant system: this includes the agricultural application of sewage sludges, and the distribution of nano-enabled agrochemicals. However, a thorough understanding of the physiological and molecular implications of ENMs dispersion and chronic low-dose exposure remains elusive, thus requiring new evidence and a more mechanistic overview of pathways and major effectors involved in plants. Plants can offer a reliable alternative to conventional model systems to elucidate the concept of ENM biotransformation within tissues and organs, as a crucial step in understanding the mechanisms of ENM-organism interaction. To facilitate the understanding of the physico-chemical forms involved in plant response, synchrotron-based techniques have added new potential perspectives in studying the interactions between ENMs and biota. These techniques are providing new insights on the interactions between ENMs and biomolecules. The present review discusses the principal outcomes for ENMs after intake by plants, including possible routes of biotransformation which make their final fate less uncertain, and therefore require further investigation.

Comparative bioaccumulation, translocation, and phytotoxicity of metal oxide nanoparticles and metal ions in soil-crop system

Exposure of the soil environment to metal nanoparticles (MNPs) has been extensive because of their indiscriminate use and the disposal of MNP products in various applications. In MNP-amended soil, various crops can absorb the nanoparticles, and accumulation of the MNPs in farm products has potential risks for bioconcentration in humans and livestock. Here, we evaluated the comparative bioaccumulation, translocation, and phytotoxicity of MNPs (ZnO and CuO NPs) and metal ions (Zn(NO3)2 and Cu(NO3)2) in four different crops, namely lettuce, radish, bok choy, and tomato. We carried out pot experiments to evaluate the phytotoxicity in the crops from the presence of MNPs and metal ions. Phytotoxicity from different treatments differed depending on the plant species, and metal types. In addition, exposure to Zn and Cu showed positive dose-dependent effects on their bioaccumulation in each crop. However, there were no significant differences in metal bioaccumulation depending on whether the crops were exposed to MNPs or metal ions. By calculating the bioconcentration factor (BCF) and translocation factor (TF), we were able to estimate the biological uptake and translocation abilities of MNPs and metal ions for each crop. It was found that lettuce and radish had greater BCFs than bok choy and tomato, while bok choy and tomato had higher TFs. Also, the uptake and translocation of Zn were better than those of Cu. However, the values for BCF and TF for each crop showed no significant differences between MNP and metal ion exposure. A micro X-ray fluorescence (μ-XRF) spectrometer analysis demonstrated that only Zn elements appeared in the primary veins and edges of all leaves and the storage root of radish. Our study aims to estimate bioaccumulation, translocation, and the implied potential risks from MNPs accumulated in different plant species.

Protein Analysis of A. halleri and N. caerulescens Hyperaccumulators When Exposed to Nano and Ionic Forms of Cd and Zn

Hyperaccumulator plant species growing on metal-rich soils can accumulate high quantity of metals and metalloids in aerial tissues, and several proteomic studies on the molecular mechanisms at the basis of metals resistance and hyperaccumulation have been published. Hyperaccumulator are also at the basis of the phytoremediation strategy to remove metals more efficiently from polluted soils or water. Arabidopsis halleri and Noccea caerulescens are both hyperaccumulators of metals and nano-metals. In this study, the change in some proteins in A. halleri and N. caerulescens was assessed after the growth in soil with cadmium and zinc, provided as sulphate salts (CdSO₄ and ZnSO₄) or sulfide quantum dots (CdS QDs and ZnS QDs). The protein extracts obtained from plants after 30 days of growth were analyzed by 2D-gel electrophoresis (2D SDS-PAGE) and identified by MALDI-TOF/TOF mass spectrometry. A bioinformatics analysis was carried out on quantitative protein differences between control and treated plants. In total, 43 proteins resulted in being significatively modulated in A. halleri, while 61 resulted in being modulated in N. caerulescens. Although these two plants are hyperaccumulator of both metals and nano-metals, at protein levels the mechanisms involved do not proceed in the same way, but at the end bring a similar physiological result.

Size- and Ligand-Dependent Transport of Nanoparticles in Matricaria chamomilla as Demonstrated by Mass Spectroscopy and X-ray Fluorescence Imaging

Matricaria chamomilla flowers were incubated with gold nanoparticles of different sizes ranging from 1.4 to 94 nm. After different incubation times of 6, 12, 24, and 48 h, the gold distribution in the flowers was destructively measured by inductively coupled plasma mass spectrometry (ICP-MS) and non-destructively measured by X-ray fluorescence imaging (XFI) with high lateral resolution. As a control, the biodistribution of iodine ions or iodine-containing organic molecules (iohexol) was determined, in order to demonstrate the feasibility of mapping the distribution of several elements in parallel. The results show a clear size-dependent transport of the nanoparticles. In addition, the surface chemistry also plays a decisive role in disposition. Only the 1.6 nm nanoparticles coated with acetylcysteine could be efficiently transported through the stem of the flowers into the petals. In this case, almost 80% of the nanoparticles which were found within each flower were located in the petals. The study also highlights the potential of XFI for in situ recording of in vivo analyte biodistribution.

Tomato Fruit Nutritional Quality Is Altered by the Foliar Application of Various Metal Oxide Nanomaterials

Carbohydrates and phytonutrients play important roles in tomato fruit’s nutritional quality. In the current study, Fe₃O₄, MnFe₂O₄, ZnFe₂O₄, Zn_0.5Mn_0.5Fe₂O₄, Mn₃O₄, and ZnO nanomaterials (NMs) were synthesized, characterized, and applied at 250 mg/L to tomato plants via foliar application to investigate their effects on the nutritional quality of tomato fruits. The plant growth cycle was conducted for a total of 135 days in a greenhouse and the tomato fruits were harvested as they ripened. The lycopene content was initially reduced at 0 stored days by MnFe₂O₄, ZnFe₂O₄, and Zn_0.5Mn_0.5Fe₂O₄; however, after a 15-day storage, there was no statistical difference between the treatments and the control. Moreover, the β-carotene content was also reduced by Zn_0.5Mn_0.5Fe₂O₄, Mn₃O₄, and ZnO. The effects of the Mn₃O₄ and ZnO carried over and inhibited the β-carotene after the fruit was stored. However, the total phenolic compounds were increased by ZnFe₂O₄, Zn_0.5Mn_0.5Fe₂O₄, and ZnO after 15 days of storage. Additionally, the sugar content in the fruit was enhanced by 118% and 111% when plants were exposed to Mn₃O₄ and ZnO, respectively. This study demonstrates both beneficial and detrimental effects of various NMs on tomato fruit quality and highlights the need for caution in such nanoscale applications during crop growth.

Functions and strategies for enhancing zinc availability in plants for sustainable agriculture

Zinc (Zn), which is regarded as a crucial micronutrient for plants, and is considered to be a vital micronutrient for plants. Zn has a significant role in the biochemistry and metabolism of plants owing to its significance and toxicity for biological systems at specific Zn concentrations, i.e., insufficient or harmful above the optimal range. It contributes to several cellular and physiological activities of plants and promotes plant growth, development, and yield. Zn is an important structural, enzymatic, and regulatory component of many proteins and enzymes. Consequently, it is essential to understand the interplay and chemistry of Zn in soil, its absorption, transport, and the response of plants to Zn deficiency, as well as to develop sustainable strategies for Zn deficiency in plants. Zn deficiency appears to be a widespread and prevalent issue in crops across the world, resulting in severe production losses that compromise nutritional quality. Considering this, enhancing Zn usage efficiency is the most effective strategy, which entails improving the architecture of the root system, absorption of Zn complexes by organic acids, and Zn uptake and translocation mechanisms in plants. Here, we provide an overview of various biotechnological techniques to improve Zn utilization efficiency and ensure the quality of crop. In light of the current status, an effort has been made to further dissect the absorption, transport, assimilation, function, deficiency, and toxicity symptoms caused by Zn in plants. As a result, we have described the potential information on diverse solutions, such as root structure alteration, the use of biostimulators, and nanomaterials, that may be used efficiently for Zn uptake, thereby assuring sustainable agriculture.