Silver nanoparticles in plant health: Physiological response to phytotoxicity and oxidative stress.

Silver nanoparticles (AgNPs) have gained significant attention in various fields due to their unique properties, but their release into the environment has raised concerns about their environmental and biological impacts. Silver nanoparticles can enter plants following their exposure to roots or via stomata following foliar exposure. Upon penetrating the plant cells, AgNPs interact with cellular components and alter physiological and biochemical processes. One of the key concerns associated with plant exposure to AgNPs is the potential of these materials to induce oxidative stress. Silver nanoparticles can also suppress plant growth and development by disrupting essential plant physiological processes, such as photosynthesis, nutrient uptake, water transport, and hormonal regulation. In crop plants, these disruptions may, in turn, affect the productivity and quality of the harvested components and therefore represent a potential threat to agricultural productivity and ecosystem stability. Understanding the phytotoxic effects of AgNPs is crucial for assessing their environmental implications and guiding the development of safe nanomaterials. By delving into the phytotoxic effects of AgNPs, this review contributes to the existing knowledge regarding their environmental risks and promotes the advancement of sustainable nanotechnological practices.

Agronomic Investigation of Spray Dispersion of Metal-Based Nanoparticles on Sunflowers in Real-World Environments.

In environmental and agronomic settings, even minor imbalances can trigger a range of unpredicted responses. Despite the widespread use of metal-based nanoparticles (NPs) and new bio-nanofertilizers, their impact on crop production is absent in the literature. Therefore, our research is focused on the agronomic effect of spray application of gold nanoparticles anchored to SiO2 mesoporous silica (AuSi-NPs), zinc oxide nanoparticles (ZnO-NPs), and iron oxide nanoparticles (Fe3O4-NPs) on sunflowers under real-world environments. Our findings revealed that the biosynthetically prepared AuSi-NPs and ZnO-NPs were highly effective in enhancing sunflower seasonal physiology, e.g., the value of the NDVI index increased from 0.012 to 0.025 after AuSi-NPs application. The distribution of leaf trichomes improved and the grain yield increased from 2.47 t ha-1 to 3.29 t ha-1 after ZnO-NPs application. AuSi-NPs treatment resulted in a higher content of essential linoleic acid (54.37%) when compared to the NPs-free control (51.57%), which had a higher determined oleic acid. No NPs or residual translocated metals were detected in the fully ripe sunflower seeds, except for slightly higher silica content after the AuSi-NPs treatment. Additionally, AuSi-NPs and NPs-free control showed wide insect biodiversity while ZnO-NPs treatment had the lowest value of phosphorus as anti-nutrient. Contradictory but insignificant effect on physiology, yield, and insect biodiversity was observed in Fe3O4-NPs treatment. Therefore, further studies are needed to fully understand the long-term environmental and agricultural sustainability of NPs applications.

Improving biofortification success rates and productivity through zinc nanocomposites in rice (Oryza sativa L.).

Rice (Oryza sativa L.) is a staple food crop; most of it is consumed in nations where malnutrition is a serious problem, and its enrichment through biofortification can be used to efficiently combat hidden hunger. Here, we studied the effect of two zinc forms, i.e., zinc oxide nanoparticles (ZnO NPs) and sulfate salt (ZnSO4), at four different concentrations during the grain development period (after anthesis and continued once a week for up to 5 weeks) of the rice plant. During the rice growing season 2021-2022, all the experiments were conducted in a greenhouse (temperature: day 30 °C; night 20 °C; relative humidity: 70%; light period: 16 h/8 h, day/night). The main aim was to identify the effects of ZnO NPs on physical growth, biochemical parameters, nutrient acquisition, and crop yield. We have also highlighted the effects of NPs on zinc biofortification, and the end results illustrated that both zinc forms are capable of increasing grain yield. However, we found that even at low concentrations, ZnO NPs showed a significant increase in growth yield, whereas bulk did not show eminent results even at higher concentrations. Spikelet number per panicle was more than 50% and 38% in the case of ZnO NPs and ZnSO4, respectively. Similarly, stimulation in plant height was 25% with NPs treatment and only 3% with bulk treatment. The increase in grain per spike was 19% with ZnO NPs as compared to the control. Total chlorophyll, soluble sugar, amylose, and soluble protein contents were enhanced under ZnO NP treatment, which plays an excellent role in the regulation of various transcriptional pathways related to biofortification. We identified that foliar application at the flowering stage is more effective in comparison to the basal and tillering stages of the rice life cycle. ZnO NPs increased zinc content in rice grain by 55% as compared to traditional fertilization (~ 35%), with no adverse effects on human health. This study highlights that ZnO NPs could be used to increase zinc efficiency and as a safe fertilizer in the rice harvesting ecosystem.

Antimicrobial therapeutics isolated from algal source: retrospect and prospect.

In the last few decades, attention on new natural antimicrobial compounds has arisen due to a change in consumer preferences and the increase in the number of resistant microorganisms. Algae are defined as photosynthetic organisms that demonstrate a wide range of adaptability to adverse environmental conditions like temperature extremes, photo-oxidation, high or low salinity, and osmotic stress. Algae are primarily known to produce large amounts of secondary metabolite against various kinds of pathogenic microbes. Among these algae, micro and microalgae of river, lake, and algae of oceanic origin have been reported to have antimicrobial activity against the bacteria and fungi of pathogenic nature. Various polar and non- polar extracts of micro- and macro algae have been used for the suppression of these pathogenic fungi. Apart from these, certain algal derivatives have also been isolated from these having antibacterial and antifungal potential. Among the bioactive molecules of algae, polysaccharides, sulphated polysaccharides, phyco-cyanobilins polyphenols, lectins, proteins lutein, vitamin E, B12 and K1, peptides, polyunsaturated fatty acids and pigments can be highlighted. In the present review, we will discuss the biological activity of these derived compounds as antifungal/ antibacterial agents and their most promising applications. A brief outline is also given for the prospects of these isolated phytochemicals and using algae as therapeutic in the dietary form. We have also tried to answer whether alga-derived metabolites can serve as potential therapeutics for the treatment of SARS-CoV-2 like viral infections too.

ß-Cyclocitral: Emerging Bioactive Compound in Plants.

ß-cyclocitral (ßCC), a main apocarotenoid of ß-carotene, increases plants' resistance against stresses. It has recently appeared as a novel bioactive composite in a variety of organisms from plants to animals. In plants, ßCC marked as stress signals that accrue under adverse ecological conditions. ßCC regulates nuclear gene expression through several signaling pathways, leading to stress tolerance. In this review, an attempt has been made to summarize the recent findings of the potential role of ßCC. We emphasize the ßCC biosynthesis, signaling, and involvement in the regulation of abiotic stresses. From this review, it is clear that discussing compound has great potential against abiotic stress tolerance and be used as photosynthetic rate enhancer. In conclusion, this review establishes a significant reference base for future research.

Effect of zinc and iron oxide nanoparticles on plant physiology, seed quality and microbial community structure in a rice-soil-microbial ecosystem.

In this study, we assessed the impact of zinc oxide (ZnO) and iron oxide (FeO) (<36 nm) nanoparticles (NPs) as well as their sulphate salt (bulk) counterpart (0, 25, 100 mg/kg) on rice growth and seed quality as well as the microbial community in the rhizosphere environment of rice. During the rice growing season 2021-22, all experiments were conducted in a greenhouse (temperature: day 30 °C; night 20 °C; relative humidity: 70%; light period: 16 h/8 h, day/night) in rice field soil. Results showed that low concentrations of FeO and ZnO NPs (25 mg/kg) promoted rice growth (height (29%, 16%), pigment content (2%, 3%)) and grain quality parameters such as grains per spike (8%, 9%), dry weight of grains (12%, 14%) respectively. As compared to the control group, the Zn (2%) and Fe (5%) accumulations at their respective low concentrations of NP treatments showed stimulation. Interestingly, our results showed that at low concentration of both the NPs the soil microbes had more diversity and richness than those in the bulk treated and control soil group. Although a number of phyla were affected by the presence of NPs, the strongest effects were observed for change in the abundance of the three phyla for Proteobacteria, Actinobacteria, and Planctomycetes. The rhizosphere environment was notably enriched with potential streptomycin producers, carbon and nitrogen fixers, and lignin degraders with regard to functional groups of microorganisms. However, microbial communities mainly responsible for chitin degradation, ammonia oxidation, and nitrite reduction were found to be decreased. The results from this study highlight significant changes in several plant-based endpoints, as well as the rhizosphere soil microorganisms. It further adds information to our understanding of the nanoscale-specific impacts of important micronutrient oxides on both rice and its associated soil microbiome.

Modulation of Cellular Redox Status and Antioxidant Defense System after Synergistic Application of Zinc Oxide Nanoparticles and Salicylic Acid in Rice (Oryza sativa) Plant under Arsenic Stress.

The objective of this research was to determine the effect of zinc oxide nanoparticles (ZnONPs) and/or salicylic acid (SA) under arsenic (As) stress on rice (Oryza sativa). ZnONPs are analyzed for various techniques viz., X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). All of these tests established that ZnONPs are pure with no internal defects, and can be potentially used in plant applications. Hence, we further investigated for better understanding of the underlying mechanisms and the extent of ZnONPs and SA induced oxidative stress damages. More restricted plant growth, gas exchange indices, significant reduction in the SPAD index and maximum quantum yield (Fv/Fm) and brutal decline in protein content were noticed in As-applied plants. In contrast, foliar fertigation of ZnONPs and/or SA to As-stressed rice plants lessens the oxidative stress, as exposed by subordinate levels of reactive oxygen species (ROS) synthesis. Improved enzymatic activities of catalase (CAT), peroxidase (POX), and superoxide dismutase (SOD), proline and total soluble protein contents under ZnONPs and SA treatment plays an excellent role in the regulation of various transcriptional pathways participated in oxidative stress tolerance. Higher content of nitrogen (N; 13%), phosphorus (P; 10%), potassium (K; 13%), zinc (Zn; 68%), manganese (Mn; 14%), and iron (Fe; 19) in ZnONPs and SA treated plants under As-stress, thus hampered growth and photosynthetic efficiency of rice plants. Our findings suggest that toxicity of As was conquering by the application of ZnONPs and SA in rice plants.

Structural analysis of extrafloral nectaries of Senna occidentalis L.: insights on diversity and evolution.

MAIN CONCLUSION: The extrafloral nectaries of S. occidentalis were studied structurally and anatomically (at secretory and post-secretory developmental stages). Role of extrafloral nectaries as a common plant-adoptive characteristic in context to diversity and phylogenetic pattern was also speculated while exploring other collaborative evolutionary implications of this plant. Extrafloral nectaries (EFNs) are widespread and evolutionarily labile traits that have repeatedly and remarkably evolved in vascular plants. Morphological descriptions of the EFNs of certain plant species are common in the literature, but they rarely relate morphology with histology, gland distribution and secretory characteristics. Studies relating EFNs features, i.e., morphology and distribution with their differential visitation by insects, viz. ants and the cost of maintenance to the plants are important to understand the evolution of these glands. Therefore, in this study a morphological, anatomical (structure and ultrastructure) and secretory characterization of EFNs occurring on Senna occidentalis L. is made with the implications of gland attributes discussed from a functional perspective. S. occidentalis L. (Caesalpiniaceae) is an economically important species from industrial, medicinal and agricultural perspective. Observations from the result showed that shape of the EFNs (size 1-2 mm) ranged to globular, ovoid-conical, dome-shaped, fusiform or cylindrical with conical tip. The EFNs were sessile, positioned interpetiolar or seated at the base of petiole. Light and transmission electron microscopic studies showed the specific internal structures of the extrafloral nectary. Two developmental stages of the EFNs (secretory and post-secretory) were recognized. Our current understanding of the phylogenetic patterns of EFNs makes them powerful candidates for future work exploring the drivers of their evolutionary origins, shifts, and losses.

Nanopriming with phytosynthesized zinc oxide nanoparticles for promoting germination and starch metabolism in rice seeds.

The application of zinc oxide nanoparticles (ZnO NPs) in agricultural field is emerging and relatively new. In this work, a simple, cost-efficient, non-toxic and eco-friendly method for the green synthesis of ZnO NPs by Senna occidentalis leaf extract has been described. Techniques used to characterize nanoparticles (NPs) were X-ray diffractometer (XRD), UV visible spectroscopy, Particle size analyzer (PSA), Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). In this study, green synthesized ZnO NPs at 20-40 mg/l solution was used to prime aged seeds of early flowering homozygous mutant (BM6) of Pusa basmati (Oryza sativa), which enhanced germination performance and seedling vigor significantly as compared to zinc sulphate (ZnSO4) priming and conventional hydropriming. The effect of treatment was analyzed by measuring biophysical and biochemical parameter of germinating rice seeds. The seeds treated with ZnO NPs of 20 mg/l concentration showed more than 50 % stimulation in dry weight, relative water uptake of seeds and radicle length of seedling in comparison to other priming solution and control (hydro-primed). Significant growth was also observed in plumule length and fresh weight of seeds in ZnO NPs at 20 mg/l concentration in comparison to control and other priming treatments. At the same concentration of ZnO NPs, there was 23 % stimulation reported in total soluble sugar content and 45 % stimulation in amylase activity. There was also a substantial increase in antioxidant enzymes i.e. superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) activity. Seed priming represents an innovative user-friendly approach to enhance the germination rate, starch metabolic process and triggered zinc acquisition of rice aged seed as an alternative to the conventional priming method.

Eco-friendly synthesis of phytochemical-capped iron oxide nanoparticles as nano-priming agent for boosting seed germination in rice (Oryza sativa L.).

Recently the applications of engineered nanoparticles in the agricultural sector is increased as nano-pesticides, nano-fertilizers, nanocarrier for macro- or micronutrients, nano-sensors, etc. In this study, biocompatible iron oxide nanoparticles (FeO NPs) have been synthesized through an environment-friendly route using Cassia occidentalis L. flower extract to act as nano-priming agent for promoting germination of Pusa basmati rice seeds. Different characterization methods, viz. X-ray diffraction, particle size analyser, zeta potential and scanning electron microscopy, were used to show efficacious synthesis of FeO NPs capped with phytochemicals. Rice seeds primed with FeO NPs at 20 and 40 mg/L efficiently enhanced germination and seedling vigour compared to ferrous sulphate (FeSO4) priming and hydro-primed control. The seeds primed with 20 mg/L FeO NPs showed up to 50% stimulation in biophysical parameters such as root length and dry weight. Substantial stimulation of sugar and amylase content was also reported at the same concentration. The antioxidant enzyme activity was significantly increased as compared to FeSO4 priming and control. Inductively coupled plasma mass spectroscopy (ICP-MS) study was also done for analysis of Fe, Zn, K, Ca, and Mn concentration in seeds. The seed priming technique signifies a comprehensible and innovative approach that could enhance α-amylase activity, iron acquisition, and ROS production, ensuing elevated soluble sugar levels for supporting seedling growth and enhancing seed germination rate, respectively. In this report, phytochemical-capped FeO NPs are presented as a capable nano-priming agent for stimulating the germination of naturally aged rice seeds.

A review of CRISPR associated genome engineering: application, advances and future prospects of genome targeting tool for crop improvement.

The Cas9 nuclease initiates double-stranded breaks at the target position in DNA, which are repaired by the intracellular restoration pathways to eliminate or insert pieces of DNA. CRISPR-Cas9 is proficient and cost-effective since cutting is guided by a piece of RNA instead of protein. Emphasis on this technology, in contrast with two recognized genome editing platforms (i.e., ZFNs and TALENs), is provided. This review evaluates the benefits of chemically synthesized gRNAs as well as the integration of chemical amendments to improve gene editing efficiencies. CRISPR is an indispensable means in biological investigations and is now as well transforming varied fields of biotechnology and agriculture. Recent advancement in targetable epigenomic-editing tools allows researchers to dispense direct functional and transcriptional significance to locus-explicit chromatin adjustments encompassing gene regulation and editing. An account of diverse sgRNA design tools is provided, principally on their target competence prediction model, off-target recognition algorithm, and generation of instructive annotations. The modern systems that have been utilized to deliver CRISPR-Cas9 in vivo and in vitro for crop improvement viz. nutritional enhancement, production of drought-tolerant and disease-resistant plants, are also highlighted. The conclusion is focused on upcoming directions, biosafety concerns, and expansive prospects of CRISPR technologies.

Identification of drought stress-responsive genes in rice (Oryza sativa) by meta-analysis of microarray data.

Meta-analysis provides a systematic access to the previously studied microarray datasets that can recognize several commonsignatures of stresses. Three different datasets of abiotic stresses on rice were used for meta-analysis. These microarray datasets were normalized to regulate data for technical variation, as opposed to biological differences between the samples. A t-test was performed to recognize the differentially-expressed genes (DEGs) between stressed and normal samples. Gene ontology enrichment analysis revealed the functional distribution of DEGs in different stressed conditions. Further analysis was carried out using software RICE NET DB and divided into three different categories: biological process (homoiothermy and protein amino acid phosphorylation), cellular component (nucleus and membrane), and molecular function (zinc ion binding ad DNA binding). The study revealed that 5686 genes were constantly expressed differentially in Oryza sativa (2089 upregulated and 3597 downregulated). The lowest P value (P = 0.003756) among upregulated DEGs was observed for naringenin, 2-oxoglutrate 3-dioxygenase protein. The lowest P value (P = 0.002866816) among the downregulated DEGs was also recorded for retrotransposon protein. The network constructed from 48 genes revealed 10 hub genes that are connected with topological genes. These hub genes are stress responsive genes that may also be regarded as the marker genes for drought stress response. Our study reported a new set of hub genes (reference genes) that have potentially significant role in development of stress tolerant rice.

A comparative screening of abiotic stress tolerance in early flowering rice mutants.

Oryza sativa L. (Rice) a grain crop grown considerably in areas frequented with abiotic stresses has a higher heat and drought tolerance and is deemed a model crop for tolerance studies. Manifold environment testing facilitates recognition of constant genotypes of rice mutants for adverse abiotic stress conditions. Mutants are an imperative genetic reserve which can help as an informative basis of natural disparity. We assessed EMS induced early flowering rice mutants (Control, BM6, BM6´ and BM9) for potential study of stress tolerance under limited water, salinity and high zinc conditions by testing for plant growth (biophysical and biochemical) traits, as well ascytotoxicity and genotoxicity determination assay via MTT and epifluoresence microscopy methods in root tissues of the mutants. Environmental effect was more significant than genotypic contribution on biophysical and biochemical parameters. BM9 mutant was found to be the most stable genotype in tolerance studies among other mutants in artificially created stress environments viz. mannitol (moderated drought), sodium chloride (salinity stress), zinc sulfate (heavy metal stress) and zinc oxide nanoparticles for a time duration. These mutants are a valuable resource for varietal advancements and to determine genes for tolerance to multiple abiotic stresses. To our knowledge this is the first account on validation of manifold abiotic stresses in early flowering rice mutants. This study can additionally assist fastidious detection of stress-tolerance genes in this vital crop.