Toxicological effects of nanoparticles in plants: Mechanisms involved at morphological, physiological, biochemical and molecular levels.

The rapid advancement of nanotechnology has led to unprecedented innovations across diverse industries, including pharmaceuticals, agriculture, cosmetics, electronics, textiles, and food, owing to the unique properties of nanoparticles. The extensive production and unregulated release of synthetic nanoparticles may contribute to nanopollution within the ecosystem. In the agricultural sector, nanotechnology is increasingly utilized to improve plant productivity, enhance resistance to stressors, and reduce the usage of chemicals. However, the uncontrolled discharge of nanoparticles into the natural environment raises concerns regarding possible plant toxicological impacts. The review focuses on the translocation of these particles within the plants, emphasizing their phytotoxicological effects at morphological, physiological, biochemical, and molecular levels. Eventhough the beneficial aspects of these nanoparticles are evident, excessive usage of nanoparticles at higher concentrations may lead to potential adverse effects. The phytotoxicity resulting from excessive amounts of nanoparticles affects seed germination and biomass production, disrupts the photosynthesis system, induces oxidative stress, impacts cell membrane integrity, alters gene expression, causes DNA damage, and leads to epigenetic variations in plants. Nanoparticles are found to directly associate with the cell membrane and cell organelles, leading to the dissolution and release of toxic ions, generation of reactive oxygen species (ROS) and subsequent oxidative stress. The present study signifies and accumulates knowledge regarding the application of nanoparticles in agriculture and illustrates a clear picture of their possible impacts on plants and soil microbes, thereby paving the way for future developments in nano-agrotechnology. The review concludes by addressing current challenges and proposing future directions to comprehend and mitigate the possible biological risks associated with nanoparticles in agriculture.

Zinc oxide nanoparticles prepared through microbial mediated synthesis for therapeutic applications: a possible alternative for plants.

Zinc oxide nanoparticles (ZnO-NPs) synthesized through biogenic methods have gained significant attention due to their unique properties and potential applications in various biological fields. Unlike chemical and physical approaches that may lead to environmental pollution, biogenic synthesis offers a greener alternative, minimizing hazardous environmental impacts. During biogenic synthesis, metabolites present in the biotic sources (like plants and microbes) serve as bio-reductants and bio-stabilizers. Among the biotic sources, microbes have emerged as a promising option for ZnO-NPs synthesis due to their numerous advantages, such as being environmentally friendly, non-toxic, biodegradable, and biocompatible. Various microbes like bacteria, actinomycetes, fungi, and yeast can be employed to synthesize ZnO-NPs. The synthesis can occur either intracellularly, within the microbial cells, or extracellularly, using proteins, enzymes, and other biomolecules secreted by the microbes. The main key advantage of biogenic synthesis is manipulating the reaction conditions to optimize the preferred shape and size of the ZnO-NPs. This control over the synthesis process allows tailoring the NPs for specific applications in various fields, including medicine, agriculture, environmental remediation, and more. Some potential applications include drug delivery systems, antibacterial agents, bioimaging, biosensors, and nano-fertilizers for improved crop growth. While the green synthesis of ZnO-NPs through microbes offers numerous benefits, it is essential to assess their toxicological effects, a critical aspect that requires thorough investigation to ensure their safe use in various applications. Overall, the presented review highlights the mechanism of biogenic synthesis of ZnO-NPs using microbes and their exploration of potential applications while emphasizing the importance of studying their toxicological effects to ensure a viable and environmentally friendly green strategy.

Fate, bioaccumulation and toxicity of engineered nanomaterials in plants: Current challenges and future prospects.

The main focus of this review is to discuss the current advancement in nano-metallic caused phytotoxicity on living organisms and current challenges in crops. Nanostructured materials provide new tools in agriculture to boost sustainable food production, but the main concern is that large-scale production and release of nanomaterials (NMs) into the ecosystem is a rising threat to the surrounding environment that is an urgent challenge to be addressed. The usage of NMs directly influences the transport pathways within plants, which directly relates to their stimulatory/ inhibitory effects. Because of the unregulated nanoparticles (NMs) exposure to soil, they are adsorbed at the root surface, followed by uptake and inter/intracellular mobility within the plant tissue, while the aerial exposure is taken up by foliage, mostly through cuticles, hydathodes, stigma, stomata, and trichomes, but the actual mode of NMs absorption into plants is still unclear. NMs-plant interactions may have stimulatory or inhibitory effects throughout their life cycle depending on their composition, size, concentration, and plant species. Although many publications on NMs interactions with plants have been reported, the knowledge on their uptake, translocation, and bioaccumulation is still a question to be addressed by the scientific community. One of the critical aspects that must be discovered and understood is detecting NMs in soil and the uptake mechanism in plants. Therefore, the nanopollution in plants has yet to be completely understood regarding its impact on plant health, making it yet another artificial environmental influence of unknown long-term consequences. The present review summarizes the uptake, translocation, and bioaccumulation of NMs in plants, focusing on their inhibitory effects and mechanisms involved within plants.

Induction of drought tolerance in Pennisetum glaucum by ACC deaminase producing PGPR- Bacillus amyloliquefaciens through Antioxidant defense system.

Rhizobacteria from pearl millet were screened to produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase and to evaluate its role in alleviating drought stress. Amongst 96 isolates, 28 were positive for ACC deaminase production, with MMR04 offering maximum activity of 2196.23 nmol of α-ketobutyrate produced mg-1 of protein h-1. The ACC deaminase producing rhizobacteria with multiple beneficial properties along with root colonization and non-pathogenic were selected [Bacillus amyloliquefaciens (MMR04), Bacillus subtilis (MMR18) and Stenotrophomonas maltophilia (MMR36)] to confirm the presence of ACC deaminase gene. A significant enhancement in seed germination (91.75%) and seedling vigor (1213.73) was noted upon seed treatment with MMR04 and hence further evaluated for its ability to induce drought stress. The seed treatment with MMR04 improved plant growth parameters and total chlorophyll and RWC in plants grown under severe drought stress (G5) conditions compared to control plants. In addition, MMR04 seed treatment enhanced proline, APX and SOD activity while decreased the MDA content up to 2.3 fold compared to untreated plants (G5). Gene expression studies revealed a significant decrease of 3.3 and 1.8 fold in the relative expression of drought-responsive (DREB-1E) and ethylene-responsive factor (ERF-1B) marker genes, respectively and an increase of 2.2 and 2.9 fold in the relative expression of APX1 and SOD1, respectively in MMR04 treated plants grown under G5 conditions over control. The results confirmed that ACC deaminase producing B. amyloliquefaciens MMR04 could defend the pearl millet plants against drought stress through an antioxidative system, thereby warranting its application in drought stress management.

Mechanisms of plant growth promotion and disease suppression by Pseudomonas aeruginosa strain 2apa.

A new Pseudomonas strain, designated as 2apa was isolated from tomato rhizosphere and identified as a member of species Pseudomonas aeruginosa based on its morphology, conventional, biochemical, cell wall fatty acid methyl ester analysis, and 16S rRNA gene sequence analysis. The strain 2apa was positive for root colonization, indole acetic acid (IAA), salicylic acid and siderophore production and inhibited the growth of wide range of microorganisms. Antimicrobial substances produced by this strain with further purification and structure elucidation proved to be phenazine. Under laboratory and greenhouse conditions the strain promoted plant growth and suppressed a wide range of foliar and root pathogens in tomato. The protection offered by strain 2apa to foliar pathogens is considered as induced systemic resistance and was further confirmed by enhanced accumulation of phenolics, elicitation of lipoxygenas activity, and jasmonic acid levels. The broad-spectrum antimicrobial and induced systemic resistance exhibiting strain P. aeruginosa 2apa can be used as an effective biological control candidate against devastating fungal and bacterial pathogens, which attack both root and foliar portions of tomato plant. Production of other functional traits such as IAA and siderophore may enhance its potential as biofertilizer.