Evolutionary analysis of tonoplast intrinsic proteins (TIPs) unraveling the role of TIP3s in plant seed development.

Tonoplast intrinsic proteins (TIPs) are crucial in facilitating the transportation of water and various small solutes across biological membranes. The evolutionary path and functional roles of TIPs is poorly understood in plants. In the present study, a total of 976 TIPs were identified in 104 diverse species and subsequently studied to trace their lineage-specific evolutionary path and tissue-specific function. Interestingly, TIPs were found to be absent in lower forms such as algae and fungi and they evolved later in primitive plants like bryophytes. Bryophytes possess a distant class of TIPs, denoted as TIP6, which is not found in higher plants. The aromatic/arginine (ar/R) selectivity filter found in TIP6 of certain liverworts share similarity with hybrid intrinsic protein (HIP), suggesting an evolutionary kinship. As plants evolved to more advanced forms, TIPs diversified into five different sub-groups (TIP1 to TIP5). Notably, TIP5 is a sub-group unique to angiosperms. The evolutionary history of the TIP subfamily reveals an interesting observation that the TIP3 subgroup has evolved within seed-bearing Spermatophyta. Further, TIPs exhibit tissue-specific expression that is conserved within various plant species. Specifically, the TIP3s were found to be exclusively expressed in seeds. Quantitative PCR analysis of TIP3s showed gradually increasing expression in soybean seed developmental stages. The expression of TIP3s in different plant species was also found to be gradually increasing during seed maturation. The results presented here address the knowledge gap concerning the evolutionary background of TIPs, specifically TIP3 in plants, and provide valuable insights for a deeper comprehension of the functions of TIPs in plants.

Silicon, a quasi-essential element: Availability in soil, fertilizer regime, optimum dosage, and uptake in plants.

The essentiality of silicon (Si) has always been a matter of debate as it is not considered crucial for the lifecycles of most plants. But beneficial effects of endogenous Si and its supplementation have been observed in many plants. Silicon plays a pivotal role in alleviating the biotic and abiotic stress in plants by acting as a physical barrier as well as affecting molecular pathways involved in stress tolerance, thus widely considered as "quasi-essential". In soil, most of Si is found in complex forms as mineral silicates which is not available for plant uptake. Monosilicic acid [Si(OH)4] is the only plant-available form of silicon (PAS) present in the soil. The ability of a plant to uptake Si is positively correlated with the PAS concentration of the soil. Since many cultivated soils often lack a sufficient amount of PAS, it has become common practice to supplement Si through the use of Si-based fertilizers in various crop cultivation systems. This review outlines the use of natural and chemical sources of Si as fertilizer, different regimes of Si fertilization, and conclude by identifying the optimum concentration of Si required to observe the beneficial effects in plants. Also, the different mathematical models defining the mineral dynamics for Si uptake at whole plant scale considering various natural factors like plant morphology, mineral distribution, and transporter expression have been discussed. Information provided here will further help in increasing understanding of Si role and thereby facilitate efficient exploration of the element as a fertilizer in crop production.

Structural assessment of OsNIP2;1 highlighted critical residues defining solute specificity and functionality of NIP class aquaporins.

INTRODUCTION: Nodulin-26-like intrinsic proteins (NIPs) are integral membrane proteins belonging to the aquaporin family, that facilitate the transport of neutral solutes across the bilayer. The OsNIP2;1 a member of NIP-III class of aquaporins is permeable to beneficial elements like silicon and hazardous arsenic. However, the atomistic cross-talk of these molecules traversing the OsNIP2;1 channel is not well understood. OBJECTIVE: Due to the lack of genomic variation but the availability of high confidence crystal structure, this study aims to highlight structural determinants of metalloid permeation through OsNIP2;1. METHODS: The molecular simulations, combined with site-directed mutagenesis were used to probe the role of specific residues in the metalloid transport activity of OsNIP2;1. RESULTS: We drew energetic landscape of OsNIP2;1, for silicic and arsenous acid transport. Potential Mean Force (PMF) construction illuminate three prominent energetic barriers for metalloid passage through the pore. One corresponds to the extracellular molecular entry in the channel, the second located on ar/R filter, and the third size constriction in the cytoplasmic half. Comparative PMF for silicic acid and arsenous acid elucidate a higher barrier for silicic acid at the cytoplasmic constrict resulting in longer residence time for silicon. Furthermore, our simulation studies explained the importance of conserved residues in loop-C and loop-D with a direct effect on pore dynamics and metalloid transport. Next we assessed contribution of predicted key residues for arsenic uptake, by functional complementation in yeast. With the aim of reducing arsenic uptake while maintaining beneficial elements uptake, we identified novel OsNIP2;1 mutants with substantial reduction in arsenic uptake in yeast. CONCLUSION: We provide a comprehensive assessment of pore lining residues of OsNIP2;1 with respect to metalloid uptake. The findings will expand mechanistic understanding of aquaporin's metalloid selectivity and facilitate variant interpretation to develop novel alleles with preference for beneficial metalloid species and reducing hazardous ones.

Biotechnology and urban agriculture: A partnership for the future sustainability.

The global population is growing rapidly, and with it, the demand for food. In the coming decades, more and more people will be living in urban areas, where land for traditional agriculture is scarce. Urban agriculture can help to meet this growing demand for food in a sustainable way. Urban agriculture is the practice of growing food in urban areas. It can be done on rooftops, balconies, vacant lots, and even in alleyways. Urban agriculture can produce a variety of crops, including fruits, vegetables, and herbs. It can also help to improve air quality, reduce stormwater runoff, and create jobs. Biotechnology can be used to improve the efficiency and sustainability of urban agriculture. Biotechnological tools can be used to develop crops that are resistant to pests and diseases, that are more tolerant of drought and heat, and that have higher yields. Biotechnology can also be used to improve the nutritional value of crops. This review article discusses the need for and importance of urban agriculture, biotechnology, and genome editing in meeting the growing demand for food in urban areas. It also discusses the potential of biotechnology to improve the sustainability of urban agriculture.

Microbial remediation and plant-microbe interaction under arsenic pollution.

Arsenic contamination in aquatic and terrestrial ecosystem is a serious environmental issue. Both natural and anthropogenic processes can introduce it into the environment. The speciation of the As determine the level of its toxicity. Among the four oxidation states of As (-3, 0, +3, and + 5), As(III) and As(V) are the common species found in the environment, As(III) being the more toxic with adverse impact on the plants and animals including human health. Therefore, it is very necessary to remediate arsenic from the polluted water and soil. Different physicochemical as well as biological strategies can be used for the amelioration of arsenic polluted soil. Among the microbial approaches, oxidation of arsenite, methylation of arsenic, biosorption, bioprecipitation and bioaccumulation are the promising transformation activities in arsenic remediation. The purpose of this review is to discuss the significance of the microorganisms in As toxicity amelioration in soil, factors affecting the microbial remediation, interaction of the plants with As resistant bacteria, and the effect of microorganisms on plant arsenic tolerance mechanism. In addition, the exploration of genetic engineering of the bacteria has a huge importance in bioremediation strategies, as the engineered microbes are more potent in terms of remediation activity along with quick adaptively in As polluted sites.

Genome-Wide Identification of Aquaporin Genes in Adzuki Bean (Vigna angularis) and Expression Analysis under Drought Stress.

The adzuki bean Vigna angularis (Wild.) is an important leguminous crop cultivated mainly for food purposes in Asian countries; it represents a source of carbohydrates, digestible proteins, minerals, and vitamins. Aquaporins (AQPs) are crucial membrane proteins involved in the transmembrane diffusion of water and small solutes in all living organisms, including plants. In this study, we used the whole genome sequence of the adzuki bean for in silico analysis to comprehensively identify 40 Vigna angularis aquaporin (VaAQP) genes and reveal how these plants react to drought stress. VaAQPs were compared with AQPs from other closely-related leguminous plants, and the results showed that mustard (Brassica rapa) (59), barrel medic (Medicago truncatula) (46), soybean (Glycine max) (66), and common bean (Phaseolus vulgaris L.) (41) had more AQP genes. Phylogenetic analysis revealed that forty VaAQPs belong to five subfamilies, with the VaPIPs (fifteen) subfamily the largest, followed by the VaNIPs (ten), VaTIPs (ten), VaSIPs (three), and VaXIPs (two) subfamilies. Furthermore, all AQP subcellular locations were found at the plasma membrane, and intron-exon analysis revealed a relationship between the intron number and gene expression, duplication, evolution, and diversity. Among the six motifs identified, motifs one, two, five, and six were prevalent in VaTIP, VaNIP, VaPIP, and VaXIP, while motifs one, three, and four were not observed in VaPIP1-3 and VaPIP1-4. Under drought stress, two of the VaAQPs (VaPIP2-1 and VaPIP2-5) showed significantly higher expression in the root tissue while the other two genes (VaPIP1-1 and VaPIP1-7) displayed variable expression in leaf tissue. This finding revealed that the selected VaAQPs might have unique molecular functions linked with the uptake of water under drought stress or in the exertion of osmoregulation to transport particular substrates rather than water to protect plants from drought. This study presents the first thorough investigation of VaAQPs in adzuki beans, and it reveals the transport mechanisms and related physiological processes that may be utilized for the development of drought-tolerant adzuki bean cultivars.

Genomic Landscape Highlights Molecular Mechanisms Involved in Silicate Solubilization, Stress Tolerance, and Potential Growth-Promoting Activity of Bacterium Enterobacter sp. LR6.

Silicon (Si) is gaining widespread attention due to its prophylactic activity to protect plants under stress conditions. Despite Si's abundance in the earth's crust, most soils do not have enough soluble Si for plants to absorb. In the present study, a silicate-solubilizing bacterium, Enterobacter sp. LR6, was isolated from the rhizospheric soil of rice and subsequently characterized through whole-genome sequencing. The size of the LR6 genome is 5.2 Mb with a GC content of 54.9% and 5182 protein-coding genes. In taxogenomic terms, it is similar to E. hormaechei subsp. xiangfangensis based on average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH). LR6 genomic data provided insight into potential genes involved in stress response, secondary metabolite production, and growth promotion. The LR6 genome contains two aquaporins, of which the aquaglyceroporin (GlpF) is responsible for the uptake of metalloids including arsenic (As) and antimony (Sb). The yeast survivability assay confirmed the metalloid transport activity of GlpF. As a biofertilizer, LR6 isolate has a great deal of tolerance to high temperatures (45 °C), salinity (7%), and acidic environments (pH 9). Most importantly, the present study provides an understanding of plant-growth-promoting activity of the silicate-solubilizing bacterium, its adaptation to various stresses, and its uptake of different metalloids including As, Ge, and Si.

Prevalence of irregular red cell antibody in transfusion recipients vis-a-vis healthy blood donors attending a tertiary care hospital in North India.

CONTEXT: Alloimmunization by foreign red cell antigens is a matter of concern as it may lead to hemolysis in transfused patients as well as fetus of pregnant females. AIMS: This study aimed to perform a comparative analysis of prevalence and type of irregular antibodies in healthy donors, vis-a-vis blood transfusion recipients. SETTINGS AND DESIGN: Blood samples of 4000 individuals comprising healthy donors, exposed patients, and nonexposed patients were collected and were analyzed for irregular antibodies. MATERIALS AND METHODS: Commercially available three-cell antigen panel was used for the antibody screening. The samples positive in antibody screen were further subjected to an extended 11-cell panel for antibody identification in low-ionic strength saline with and without enzyme. STATISTICAL ANALYSIS: Statistical analysis was done using SPSS for Windows 15.0 program. Chi-square test was used for detecting statistical significance of exposure to red blood cell antigens in the formation of alloantibodies. RESULTS: Of the 4000 samples, antibodies were identified in 105 (2.6%) samples. Overall, nonexposed group showed a seropositivity of 0.36%, while the exposed group showed a seropositivity of 9.4%. Anti-D was the most common antibody found in 38 patients (33.3%). Anti-E was the most common antibody in males, while anti-D was the most common antibody in females. CONCLUSIONS: Since the risk of alloimmunization is more common in multitransfused patients, it is advisable to screen at least those cases for irregular antibodies.

Silicon nanoforms in crop improvement and stress management.

Although, silicon - the second most abundant element in the earth crust could not supersede carbon (C) in the competition of being the building block of life during evolution, yet its presence has been reported in some life forms. In case of the plants, silicon has been reported widely to promote the plant growth under normal as well as stressful situations. Nanoform of silicon is now being explored for its potential to improve plant productivity and its tolerance against various stresses. Silicon nanoparticles (SiNPs) in the form of nanofertilizers, nanoherbicides, nanopesticides, nanosensors and targeted delivery systems, find great utilization in the field of agriculture. However, the mechanisms underlying their uptake by plants need to be deciphered in detail. Silicon nanoformss are reported to enhance plant growth, majorly by improving photosynthesis rate, elevating nutrient uptake and mitigating reactive oxygen species (ROS)-induced oxidative stress. Various studies have reported their ability to provide tolerance against a range of stresses by upregulating plant defense responses. Moreover, they are proclaimed not to have any detrimental impacts on environment yet. This review includes the up-to-date information in context of the eminent role of silicon nanoforms in crop improvement and stress management, supplemented with suggestions for future research in this field.

Understanding the role of SWEET genes in fruit development and abiotic stress in pomegranate (Punica granatum L.).

BACKGROUND: The Sugar Will Eventually Be Exported Transporters (SWEET), consisting of the MtN3 and salvia domain, are sugar transporters having an active role in diverse activities in plants such as pollen nutrition, phloem loading, nectar secretion, reproductive tissue development, and plant-pathogen interaction. The SWEET genes have been characterized only in a few fruit crop species. METHODS AND RESULTS: In this study, a total of 15 SWEET genes were identified in the pomegranate (Punica granatum) genome. The gene structure, transmembrane (TM) helices, domain architecture, and phylogenetic relationships of these genes were evaluated using computational approaches. Genes were further classified as Semi-SWEETs or SWEETs based on the TM domains. Similarly, pomegranate, Arabidopsis, rice, and soybean SWEETs were studied together to classify into major groups. In addition, analysis of RNAseq transcriptome data was performed to study SWEEET gene expression dynamics in different tissue. The expression suggests that SWEETs are mostly expressed in pomegranate peel. In addition, PgSWEET13 was found to be differentially expressed under high salinity stress in pomegranate. Further, quantitative PCR analysis confirmed the expression of four candidate genes in leaf and stem tissues. CONCLUSION: The information provided here will help to understand the role of SWEET genes in fruit development and under abiotic stress conditions in pomegranate.

Outstanding Questions on the Beneficial Role of Silicon in Crop Plants.

Silicon (Si) is widely accepted as a beneficial element for plants. Despite the substantial progress made in understanding Si transport mechanisms and modes of action in plants, several questions remain unanswered. In this review, we discuss such outstanding questions and issues commonly encountered by biologists studying the role of Si in plants in relation to Si bioavailability. In recent years, advances in our understanding of the role of Si-solubilizing bacteria and the efficacy of Si nanoparticles have been made. However, there are many unknown aspects associated with structural and functional features of Si transporters, Si loading into the xylem, and the role of specialized cells like silica cells and compounds preventing Si polymerization in plant tissues. In addition, despite several 1,000 reports showing the positive effects of Si in high as well as low Si-accumulating plant species, the exact roles of Si at the molecular level are yet to be understood. Some evidence suggests that Si regulates hormonal pathways and nutrient uptake, thereby explaining various observed benefits of Si uptake. However, how Si modulates hormonal pathways or improves nutrient uptake remains to be explained. Finally, we summarize the knowledge gaps that will provide a roadmap for further research on plant silicon biology, leading to an exploration of the benefits of Si uptake to enhance crop production.

Exploration of silicate solubilizing bacteria for sustainable agriculture and silicon biogeochemical cycle.

Silicon (Si), a quasi-essential element for plants, is abundant in the soil typically as insoluble silicate forms. However, plants can uptake Si only in the soluble form of monosilicic acid. Production of monosilicic acid by rock-weathering mostly depends on temperature, pH, redox-potential, water-content, and microbial activities. In the present review, approaches involved in the efficient exploration of silicate solubilizing bacteria (SSB), its potential applications, and available technological advances are discussed. Present understanding of Si uptake, deposition, and subsequent benefits to plants has also been discussed. In agricultural soils, pH is found to be one of the most critical factors deciding silicate solubilization and the formation of different Si compounds. Numerous studies have predicted the role of Indole-3-Acetic Acid (IAA) and organic acids produced by SSB in silicate solubilization. In this regard, approaches for the isolation and characterization of SSB, quantification of IAA, and subsequent Si solubilization mechanisms are addressed. Phylogenetic evaluation of previously reported SSB showed a highly diverse origin which provides an opportunity to study different mechanisms involved in Si solubilization. Soil biochemistry in concern of silicon availability, microbial activity and silicon mediated changes in plant physiology are addressed. In addition, SSB's role in Si-biogeochemical cycling is summarized. The information presented here will be helpful to explore the potential of SSB more efficiently to promote sustainable agriculture.

Role of silicon in elevating resistance against sheath blight and blast diseases in rice (Oryza sativa L.).

Rice blast caused by Magnaporthe oryzae and sheath blight caused by Rhizoctonia solani, are the two major diseases of rice that cause enormous losses in rice production worldwide. Identification and utilization of broad-spectrum resistance resources have been considered sustainable and effective strategies. However, the majority of the resistance genes and QTLs identified have often been found to be race-specific, and their resistance is frequently broken down due to continuous exposure to the pathogen. Therefore, integrated approaches to improve plant resistance against such devastating pathogen have great importance. Silicon (Si), a beneficial element for plant growth, has shown to provide a prophylactic effect against many pathogens. The application of Si helps the plants to combat the disease-causing pathogens, either through its deposition in different parts of the plant or through modulation/induction of specific defense genes by yet an unknown mechanism. Some reports have shown that Si imparts resistance to rice blast and sheath blight. The present review summarizes the mechanism of Si transport and deposition and its effect on rice growth and development. A special emphasis has been given to explore the existing evidence showing Si mediated blast and sheath blight resistance and the mechanism involved in resistance. This review will help to understand the prophylactic effects of Si against sheath blight and blast disease at the mechanical, physiological, and genetic levels. The information provided here will help develop a strategy to explore Si derived benefits for sustainable rice production.

Versatile role of silicon in cereals: Health benefits, uptake mechanism, and evolution.

Silicon (Si) is an omnipresent and second most abundant element in the soil lithosphere after oxygen. Silicon being a beneficial element imparts several benefits to the plants and animals. In many plant species, including the cereals the uptake of Si from the soil even exceeds the uptake of essential nutrients. Cereals are the monocots which are known to accumulate a high amount of Si, and reaping maximum benefits associated with it. Cereals contribute a high amount of Si to the human diet compared to other food crops. In the present review, we have summarized distribution of the dietary Si in cereals and its role in the animal and human health. The Si derived benefits in cereals, specifically with respect to biotic and abiotic stress tolerance has been described. We have also discussed the molecular mechanism involved in the Si uptake in cereals, evolution of the Si transport mechanism and genetic variation in the Si concentration among different cultivars of the same species. Various genetic mutants deficient in the Si uptake have been developed and many QTLs governing the Si accumulation have been identified in cereals. The existing knowledge about the Si biology and available resources needs to be explored to understand and improve the Si accumulation in crop plants to achieve sustainability in agriculture.

Recent approaches for enhanced production of microbial polyhydroxybutyrate: Preparation of biocomposites and applications.

In modern decades, an increase in environmental awareness has attracted the keen interest of researchers to investigate eco-sustainable, recyclable materials to minimize reliance on petroleum-based polymeric compounds. Poly (3-hydroxybutyrate) is amorphous, linear, and biodegradable bacterial polyesters that belong to the polyhydroxyalkanoates family with enormous applications in many fields. The present review provides comprehensive information on polyhydroxybutyrate production from different biomass feedstock. Various studies on PHB production by genetically engineered bacterial cells and optimization of parameters have been discussed. Recent technological innovation in processing polyhydroxybutyrate-based biocomposite through the different process has also been examined. Besides this, the potential applications of the derived competent biocomposites in the other fields have been depicted.

Fascinating role of silicon to combat salinity stress in plants: An updated overview.

Salt stress limits plant growth and productivity by severely impacting the fundamental physiological processes. Silicon (Si) supplementation is considered one of the promising methods to improve plant resilience under salt stress. Here, the role of Si in modulating physiological and biochemical processes that get adversely affected by high salinity, is discussed. Although numerous reports show the beneficial effects of Si under stress, the precise molecular mechanism underlying this is not well understood. Questions like whether all plants are equally benefitted with Si supplementation despite having varying Si uptake capability and salinity tolerance are still elusive. This review illustrates the Si uptake and accumulation mechanism to understand the direct or indirect participation of Si in different physiological processes. Evaluation of plant responses at transcriptomics and proteomics levels are promising in understanding the role of Si. Integration of physiological understanding with omics scale information highlighted Si supplementation affecting the phytohormonal and antioxidant responses under salinity as a key factor defining improved resilience. Similarly, the crosstalk of Si with lignin and phenolic content under salt stress also seems to be an important phenomenon helping plants to reduce the stress. The present review also addressed various crucial mechanisms by which Si application alleviates salt stress, such as a decrease in oxidative damage, decreased lipid peroxidation, improved photosynthetic ability, and ion homeostasis. Besides, the application and challenges of using Si-nanoparticles have also been addressed. Comprehensive information and discussion provided here will be helpful to better understand the role of Si under salt stress.

Significance of solute specificity, expression, and gating mechanism of tonoplast intrinsic protein during development and stress response in plants.

Tonoplast intrinsic proteins (TIPs), belonging to the aquaporin family, are transmembrane channels located mostly at the tonoplast of plant cells. The TIPs are known to transport water and many other small solutes such as ammonia, urea, hydrogen peroxide, and glycerol. In the present review, phylogenetic distribution, structure, transport dynamics, gating mechanism, sub-cellular localization, tissue-specific expression, and co-expression of TIPs are discussed to define their versatile role in plants. Based on the phylogenetic distribution, TIPs are classified into five distinct groups with aromatic-arginine (Ar/R) selectivity filters, typical pore-morphology, and tissue-specific gene expression patterns. The tissue-specific expression of TIPs is conserved among diverse plant species, more particularly for TIP3s, which are expressed exclusively in seeds. Studying TIP3 evolution will help to understand seed development and germination. The solute specificity of TIPs plays an imperative role in physiological processes like stomatal movement and vacuolar sequestration as well as in alleviating environmental stress. TIPs also play an important role in growth and developmental processes like radicle protrusion, anther dehiscence, seed germination, cell elongation, and expansion. The gating mechanism of TIPs regulates the solute flow in response to external signals, which helps to maintain the physiological functions of the cell. The information provided in this review is a base to explore TIP's potential in crop improvement programs.

Histochemical Techniques in Plant Science: More Than Meets the Eye.

Histochemistry is an essential analytical tool interfacing extensively with plant science. The literature is indeed constellated with examples showing its use to decipher specific physiological and developmental processes, as well as to study plant cell structures. Plant cell structures are translucent unless they are stained. Histochemistry allows the identification and localization, at the cellular level, of biomolecules and organelles in different types of cells and tissues, based on the use of specific staining reactions and imaging. Histochemical techniques are also widely used for the in vivo localization of promoters in specific tissues, as well as to identify specific cell wall components such as lignin and polysaccharides. Histochemistry also enables the study of plant reactions to environmental constraints, e.g. the production of reactive oxygen species (ROS) can be traced by applying histochemical staining techniques. The possibility of detecting ROS and localizing them at the cellular level is vital in establishing the mechanisms involved in the sensitivity and tolerance to different stress conditions in plants. This review comprehensively highlights the additional value of histochemistry as a complementary technique to high-throughput approaches for the study of the plant response to environmental constraints. Moreover, here we have provided an extensive survey of the available plant histochemical staining methods used for the localization of metals, minerals, secondary metabolites, cell wall components, and the detection of ROS production in plant cells. The use of recent technological advances like CRISPR/Cas9-based genome-editing for histological application is also addressed. This review also surveys the available literature data on histochemical techniques used to study the response of plants to abiotic stresses and to identify the effects at the tissue and cell levels.

Silicon nanoparticles (SiNPs) in sustainable agriculture: major emphasis on the practicality, efficacy and concerns.

Silicon (Si), a beneficial element for plants, is known for its prophylactic effect under stress conditions. Many studies have documented the role of biogenic silica (bulk-Si) in alleviating biotic and abiotic stresses in plants. The scarce amount of the plant-available form of Si (monosilicic acid) in most of the cultivated soil and the limited efficacy of silicate fertilizers (bulk-Si) are the major concerns for the exploration of Si-derived benefits. In this regard, recent advances in nanotechnology have opened up new avenues for crop improvement, where plants can derive benefits associated with Si nanoparticles (SiNPs). Most of the studies have shown the positive effect of SiNPs on the growth and development of plants specifically under stress conditions. In contrast, a few studies have also reported their toxic effects on some plant species. Hence, there is a pertinent need for elaborative research to explore the utility of SiNPs in agriculture. The present review summarizes SiNP synthesis, application, uptake, and role in stimulating plant growth and development. The advantages of SiNPs over conventional bulk-Si fertilizers in agriculture, their efficacy in different plant species, and safety concerns have also been discussed. The gaps in our understanding of various aspects of SiNPs in relation to plants have also been highlighted, which will guide future research in this area. The increased attention towards SiNP-related research will help to realize the true potential of SiNPs in agriculture.

Significance of silicon uptake, transport, and deposition in plants.

Numerous studies have shown the beneficial effects of silicon (Si) for plant growth, particularly under stress conditions, and hence a detailed understanding of the mechanisms of its uptake, subsequent transport, and accumulation in different tissues is important. Here, we provide a thorough review of our current knowledge of how plants benefit from Si supplementation. The molecular mechanisms involved in Si transport are discussed and we highlight gaps in our knowledge, particularly with regards to xylem unloading and transport into heavily silicified cells. Silicification of tissues such as sclerenchyma, fibers, storage tissues, the epidermis, and vascular tissues are described. Silicon deposition in different cell types, tissues, and intercellular spaces that affect morphological and physiological properties associated with enhanced plant resilience under various biotic and abiotic stresses are addressed in detail. Most Si-derived benefits are the result of interference in physiological processes, modulation of stress responses, and biochemical interactions. A better understanding of the versatile roles of Si in plants requires more detailed knowledge of the specific mechanisms involved in its deposition in different tissues, at different developmental stages, and under different environmental conditions.