The Role of Nano-Particles in Nitrogen Uptake or Utilization in Plants: A Review of Recent Advances and Challenges

Nitrogen is an essential nutrient for plant growth and development, but it is often limiting in the soil due to various factors such as low availability, high leaching, and denitrification. Therefore, improving the efficiency of nitrogen uptake and utilization by plants is a major goal for agricultural and environmental sustainability. Nano-particles, which are materials with at least one dimension between 1 and 100 nanometers, have emerged as a promising tool to enhance the delivery and assimilation of nitrogen in plants. Nano-particles can interact with plant roots, leaves, and cells, and modulate the physiological and biochemical processes related to nitrogen metabolism. Nano-particles can also affect the soil microbial community and the nitrogen cycle, thereby influencing the availability and fate of nitrogen in the soil-plant system. However, the use of nano-particles for nitrogen management also poses some challenges and risks, such as the potential toxicity, accumulation, and translocation of nano-particles in plants and the environment. Therefore, a comprehensive understanding of the mechanisms, benefits, and drawbacks of nano-particles in nitrogen uptake or utilization in plants is needed to optimize their application and minimize their adverse impacts.?

Nano-Particles and Nitrogen Uptake by Plants:

Nano-particles can enhance the uptake of nitrogen by plants through different mechanisms, such as increasing the solubility, mobility, and availability of nitrogen sources, facilitating the transport and absorption of nitrogen across the root membrane, and stimulating the root growth and development. Some examples of nano-particles that have been shown to improve the uptake of nitrogen by plants are:?

• Nano-hydroxyapatite (nHAP), which is a biocompatible and biodegradable nano-particle that can adsorb ammonium and nitrate ions and release them slowly in the soil solution, thus reducing the leaching and volatilization losses of nitrogen and increasing its availability for plants. nHAP can also enhance the root surface area, length, and volume, and promote the expression of nitrate and ammonium transporters in the root cells, thereby improving the absorption and assimilation of nitrogen by plants.?

• Nano-zeolite, which is a porous and crystalline nano-particle that can exchange cations with the soil solution and act as a carrier and slow-release agent of nitrogen. Nano-zeolite can also increase the water-holding capacity and porosity of the soil, and improve the soil structure and fertility, thus creating a favorable environment for the root growth and nitrogen uptake by plants.?

• Nano-iron oxide (nFe2O3), which is a magnetic and reactive nano-particle that can oxidize ammonium to nitrate and reduce nitrate to ammonium, depending on the soil redox conditions and pH, thus regulating the nitrogen forms and availability for plants. nFe2O3 can also enhance the root biomass, length, and surface area, and increase the expression of nitrate reductase and glutamine synthetase in the root cells, thereby facilitating the reduction and assimilation of nitrogen by plants.?

Nano-Particles and Nitrogen Utilization by Plants:

Nano-particles can also enhance the utilization of nitrogen by plants through different mechanisms, such as improving the photosynthesis, transpiration, and respiration rates, modulating the signaling and gene expression related to nitrogen metabolism, and increasing the synthesis and accumulation of nitrogen-containing compounds. Some examples of nano-particles that have been shown to improve the utilization of nitrogen by plants are:?

• Nano-titanium dioxide (nTiO2), which is a photocatalytic and biocompatible nano-particle that can absorb and scatter light and generate reactive oxygen species, thus enhancing the photosynthesis, transpiration, and respiration rates of plants. nTiO2 can also increase the activity and expression of enzymes and genes involved in the nitrogen metabolism, such as nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase, thereby increasing the reduction, assimilation, and translocation of nitrogen by plants.?

• Nano-silver (nAg), which is a biocidal and antimicrobial nano-particle that can inhibit the growth and activity of pathogenic and non-beneficial microorganisms in the soil and on the plant surface, thus reducing the competition and interference for nitrogen and other nutrients. nAg can also stimulate the production and accumulation of phytohormones, such as auxin, cytokinin, and gibberellin, and modulate the signaling and gene expression related to the nitrogen metabolism, such as nitric oxide, nitrate, and ammonium, thereby enhancing the growth, development, and yield of plants.?

• Nano-carbon (nC), which is a versatile and multifunctional nano-particle that can act as a carrier, adsorbent, and catalyst of nitrogen and other nutrients. nC can also improve the electrical conductivity, water retention, and gas exchange of the soil and the plant, and increase the activity and expression of enzymes and genes involved in the nitrogen metabolism, such as nitrate reductase, glutamine synthetase, glutamate synthase, and glutamate dehydrogenase, thereby enhancing the assimilation, translocation, and storage of nitrogen by plants.?

Challenges and Risks of Nano-Particles in Nitrogen Uptake or Utilization in Plants:

Despite the potential benefits of nano-particles in nitrogen uptake or utilization by plants, there are also some challenges and risks that need to be addressed and overcome, such as the uncertainty, variability, and complexity of the interactions and effects of nano-particles in the soil-plant system, the lack of standardized and reliable methods and protocols for the synthesis, characterization, and application of nano-particles, the possible toxicity, accumulation, and translocation of nano-particles in plants and the environment, and the ethical, social, and regulatory implications of the use of nano-particles for nitrogen management. Therefore, more research and development are needed to understand the mechanisms, optimize the conditions, evaluate the impacts, and ensure the safety and sustainability of nano-particles in nitrogen uptake or utilization by plants.?

Nano-particles are emerging as a promising tool to enhance the uptake and utilization of nitrogen by plants, which can improve the plant growth and productivity, and reduce the environmental pollution and greenhouse gas emissions. Nano-particles can interact with plant roots, leaves, and cells, and modulate the physiological and biochemical processes related to nitrogen metabolism. Nano-particles can also affect the soil microbial community and the nitrogen cycle, thereby influencing the availability and fate of nitrogen in the soil-plant system. However, the use of nano-particles for nitrogen management also poses some challenges and risks, such as the potential toxicity, accumulation, and translocation of nano-particles in plants and the environment. Therefore, a comprehensive understanding of the mechanisms, benefits, and drawbacks of nano-particles in nitrogen uptake or utilization by plants is needed to optimize their application and minimize their adverse impacts.?