The beneficial effects of silicon and its role for plants are well established; however, the advantages of silicon nanoparticles over its bulk material are an area that is less explored. Silicon nanoparticles have distinctive physiological characteristics that allow them to enter plants and influence plant metabolic activities. The mesoporous nature of silicon nanoparticles also makes them good candidates as suitable nanocarriers for different molecules that may help in agriculture. Several studies have shown the importance of silicon nanoparticles in agriculture, but an overview of the related aspects was missing. Therefore, this review brings together the literature on silicon nanoparticles and discusses the impact of silicon nanoparticles on several aspects of agricultural sciences. The review also discusses the future application of silicon nanoparticles in plant growth, plant development, and improvement of plant productivity.

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Application of silicon nanoparticles in agriculture

Silicon (Si): Review and future prospects on the action mechanisms in alleviating biotic and abiotic stresses in plants.

Microplastics in the environment: Interactions with microbes and chemical contaminants

In the current scenario, it is an urgent requirement to satisfy the nutritional demands of the rapidly growing global population. Using conventional farming, nearly one-third of the crops get damaged mainly due to pest infestation, microbial attacks, natural disasters, poor soil quality, and lesser nutrient availability. More innovative technologies are immediately required to overcome these issues. In this regard, nanotechnology has contributed to the agrotechnological revolution that has imminent potential to reform the resilient agricultural system, while promising food security. Therefore, nanoparticles are becoming a new-age material to transform modern agricultural practices. The variety of nanoparticles-based formulations, including, nano-sized pesticides, herbicides, fungicides, fertilizers, and sensors, have been widely investigated for plant health management and soil improvement. In-depth understanding of plant and nanomaterial interactions opens new avenues towards improving crop practices through increased properties like disease resistance, crop yield, and nutrient utilization. In this review, we highlight the critical points to address the current nanotechnology-based agricultural research that could benefit productivity and food security in future.

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Nanoparticle-Based Sustainable Agriculture and Food Science: Recent Advances and Future Outlook

Plants are sessile organisms and, in order to defend themselves against exogenous (a)biotic constraints, they synthesize an array of secondary metabolites which have important physiological and ecological effects. Plant secondary metabolites can be classified into four major classes: terpenoids, phenolic compounds, alkaloids and sulphur-containing compounds. These phytochemicals can be antimicrobial, act as attractants/repellents, or as deterrents against herbivores. The synthesis of such a rich variety of phytochemicals is also observed in undifferentiated plant cells under laboratory conditions and can be further induced with elicitors or by feeding precursors. In this review, we discuss the recent literature on the production of representatives of three plant secondary metabolite classes: artemisinin (a sesquiterpene), lignans (phenolic compounds) and caffeine (an alkaloid). Their respective production in well-known plants, i.e., Artemisia, Coffea arabica L., as well as neglected species, like the fibre-producing plant Urtica dioica L., will be surveyed. The production of artemisinin and caffeine in heterologous hosts will also be discussed. Additionally, metabolic engineering strategies to increase the bioactivity and stability of plant secondary metabolites will be surveyed, by focusing on glycosyltransferases (GTs). We end our review by proposing strategies to enhance the production of plant secondary metabolites in cell cultures by inducing cell wall modifications with chemicals/drugs, or with altered concentrations of the micronutrient boron and the quasi-essential element silicon.

https://www.mdpi.com/2073-4425/9/6/309/pdf/1

Production of Plant Secondary Metabolites: Examples, Tips and Suggestions for Biotechnologists.

Elemental silicon (Si), after oxygen, is the second most abundant element in the earth’s crust, which is mainly composed of silicates. Si is not considered essential for plant growth and development, however increasing evidence in the literature shows that this metalloid is beneficial to plants, especially under stress conditions. Indeed Si alleviates the toxic effects caused by abiotic stresses, e.g. salt stress, drought, heavy metals, to name a few. Biogenic silica is also a deterrent against herbivores. Additionally, Si ameliorates the vigour of plants and improves their resistance to exogenous stresses. The protective role of Si was initially attributed to a physical barrier fortifying the cell wall (e.g. against fungal hyphae penetration), however several studies have shown that the action of this element on plants is far more complex, as it involves a cross-talk with the cell interior and an effect on plant metabolism. In this study the beneficial role of Si on plants will be discussed, by reviewing the available data in the literature. Emphasis will be given to the protective role of Si during (a)biotic stresses and in this context both priming and the effects of Si on endogenous phytohormones will be discussed. A whole section will be devoted to the use of silica (SiO2) nanoparticles, in the light of the interest that nanotechnology has for agriculture. The paper also discusses the potential technological aspects linked to the use of Si in agriculture and to modify/improve the physical parameters of plant fibers. The study indeed provides perspectives on

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Silicon and Plants: Current Knowledge and Technological Perspectives.

Reactive oxygen species and heavy metal stress in plants: Impact on the cell wall and secondary metabolism

Silicon (Si) is an abundant element which, when supplied to plants, confers increased vigor and resistance to exogenous stresses, as well as enhanced stem mechanical strength. Plant species vary in their ability to take Si up and to accumulate it under the form of silicon dioxide (SiO2) in their tissues: emblematic of this is the example of Poales, among which there is rice, a high Si accumulator. Monocots usually accumulate more Si than dicots; however, the impact that Si has on dicots, notably on economically important dicots, is a subject requiring further study and scientific efforts. In this review, we discuss the impact that Si has on bast fibre-producing plants, because of the potential importance that this element has in sustainable agriculture practices and in light of the great economic value of fibre crops in fostering a bio-economy. We discuss the data already available in the literature, as well as our own research on textile hemp. In particular, we demonstrate the beneficial effect of Si under heavy metal stress, by showing an increase in the leaf fresh weight under growth on Cd 20 µM. Additionally, we propose an effect of Si on bast fibre growth, by suggesting an action on the endogenous phytohormone levels and a mechanical role involved in the resistance to the turgor pressure during elongation. We conclude our survey with a description of the industrial and agricultural uses of Si-enriched plant biomass, where woody fibres are included in the survey.

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Impact of Silicon in Plant Biomass Production: Focus on Bast Fibres, Hypotheses, and Perspectives

Impact of cadmium and zinc on proteins and cell wall-related gene expression in young stems of hemp (Cannabis sativa L.) and influence of exogenous silicon

Textile hemp (Cannabis sativa L.) is a non-edible multipurpose crop suitable for fiber production and/or phytoremediation on moderately heavy metal-contaminated soils. Experiments were conducted in nutrient solution to assess the short-term impact of silicon (Si), a well-known beneficial element, on plants exposed to 20 μM cadmium (Cd) in nutrient solution. Cd decreased plant growth and affected photosynthesis through non-stomatal effects. Cd translocation factor was higher than 1, confirming the interest of hemp for phytoextraction purposes. Additional Si did not improve plant growth after 1 week of treatment but decreased Cd accumulation in all organs and improved water use efficiency through a decrease in transpiration rate. Si had only marginal impact on Cd distribution among organs. It increased glutathione and phytochelatin synthesis allowing the plants to efficiently cope with oxidative stress through the improvement of Cd sequestration on thiol groups in the roots. Si may thus have a fast impact on the plant behavior before the occurrence of plant growth stimulation.

Silicon reduces cadmium absorption and increases root-to-shoot translocation without impacting growth in young plants of hemp (Cannabis sativa L.) on a short-term basis

Marie Luyckx

Papers

Silicon and Plants: Current Knowledge and Technological Perspectives.

Reactive oxygen species and heavy metal stress in plants: Impact on the cell wall and secondary metabolism

Impact of Silicon in Plant Biomass Production: Focus on Bast Fibres, Hypotheses, and Perspectives

Impact of cadmium and zinc on proteins and cell wall-related gene expression in young stems of hemp (Cannabis sativa L.) and influence of exogenous silicon

Silicon reduces cadmium absorption and increases root-to-shoot translocation without impacting growth in young plants of hemp (Cannabis sativa L.) on a short-term basis