An international team of agrichemical researchers have just concluded an in-depth analysis of silicon nanoparticles finding them to be a powerful and versatile tool that is still under-used in the agricultural industry.

While the benefits of silicon as a bulk fertilizer additive have long been known, its properties at the nanoscale are still being discovered. As such, the researchers believed that a comprehensive overview of how silicon nanoparticles are being used and the impact they can have on crop output was warranted.

A: The positive effect of silicon used as a bulk fertilizer. B: Diagram of how a silica layer aids plant defences.

The work, partially funded by the Slovak Research and Development Agency and the National Science Centre Poland, established the properties and uses of silicon at a nanoparticle scale. In particular, the study focused on the following applications;

1. Direct impact of Silicon Nanoparticles on plants

The analysis concluded that, “In most studies, Si-NPs were observed to be beneficial to or ineffective for plants by either supporting plant growth or having no impact.”

While some studies did find that Si-NPs had a negative impact on plant growth this was largely associated with, “… the change in pH in growth media that occurred due to the addition of Si-NPs.”

Such is the wide-range of research that has been conducted on the effect of Si-NPs on plant growth that it is not possible to list all the results here, however the full study can be found at the National Center for Biotechnology Information.

However, the results included, among others, these findings; “… Si-NPs were observed to alleviate the negative impact of UVB radiation… Si-NPs facilitated photosynthetic activity and plant growth… Si-NPs together with Cr(VI) was observed to protect pea seedlings against Cr(VI) phytotoxicity… Si-NPs were observed to slightly improve flowering when compared with Si or the control…Si-NPs alleviated the impact of salinity stress… Si-NP-treated maize was observed to contain higher silica than micro-Si-treated maize or the control. Root elongation was also observed to be significantly increased…SiO2 was observed to significantly enhance seed germination, mean germination time, seed germination index, seed vigor index, seedling fresh weight, and dry weight.”

2. Silicon Nanoparticles as a Delivery System for Herbicides and Fertilizers

Much of the power of nanoparticles is their ability to easily access the inner working of a plant, influencing cell growth and metabolism. This makes the use of nanoparticles of silicon a highly effective way to deliver other chemicals with either herbicidal or fertilizing properties. The research found that Si-NPs have been successfully used as a carrying agent for target-specific delivery systems.

Specifically, the report states that, “Silicon nanocarriers have been observed to carry herbicides (chloroacetanilide, anilide, and benzimidazole) embedded in a diatom fistule and deliver the herbicide to the field in its active form. In the case of fertilizer delivery, studies signified that the application of nano-silicon dioxide with organic fertilizer was used to improve plant productivity.”

3.The Use of Silicon Nanoparticles in Targeted Delivery of Nucleotides, Proteins, and Chemicals in Plants

The report also uncovered a large number of studies that had focused on nanoencapsulation for controlled and regulated release of agrochemicals. While uptake and impact of this approach varied greatly from crop to crop, the method was found to be successful for some plants as a ‘site-targeted delivery means’ for various macromolecules, such as proteins, nucleotides, and other chemicals.

Specifically, the report observes 3 key novel uses for Si-NPs;

1. “Mesoporous silicon nanoparticles (MSNs) have chemically and thermally stable structures with large surface areas, tunable pore sizes, and several well-characterized surface properties, which makes them suitable for hosting guest molecules. In addition, the size-adjustable 3D open pore structure allows the regulation of adsorption rates to create effective delivery carriers.”

2. “Surface-coated MSNs were useful for DNA and SiRNA delivery due to their binding affinity and high cellular uptake. [As well as for] … the transportation of DNA and chemicals (with the gene and its chemical inducer) into isolated plant cells and intact leaves through MSNs.”

3. “The direct delivery of a Cre recombinase protein through gold-plated MSNs was also successfully achieved by a biolistic method in maize.”

This led the researchers to conclude that, “MSNPs have become established as transportation materials and have the potential to be used for the development of genetically modified crops.”

4. Silicon Nanoparticles as a Component of Nanozeolite for Increasing Water Holding Capacity

The report also found a large body of work that had used nanotechnology to improve soil health. As natural zeolites are known to aid soil quality as an important alternative to overcome the effects of drought, a body of work has focused on employing nanosized zeolites to reach the same goal.

As the study states, “Zeolites and nanozeolites facilitate water infiltration and retention in the soil due to their porous and capillary properties. Zeolites are known to act as natural wetting agents and work as water distributors throughout the soil, ultimately affecting water conduction in plants. Thus, the observed results clearly showed the ability of Si-NPs to enhance the water holding capacity and, therefore, improve soil quality.”

Ultimately, the researchers conclude that, “Si-NPs have the potential to revolutionize the existing technology used in various sectors, such as agriculture and plant biotechnology. These nanoparticles can provide green and eco-friendly alternatives to various chemical fertilizers without harming nature. Thus, Si-NPs may have concrete solutions to many agricultural problems regarding weeds, pathogenicity, drought, crop yield, and productivity.”

Photo credit: Nanogloss, NCBI, SciTechDaily, Getnanomaterials, Frontiersin, & SciTechDaily