1、Nitrogen assimilation in plants: current status and future prospects

To increase grain yields, large amounts of fertilizers, especially nitrogen (N) fertilizers, are applied during agricultural production; however, only 30%–50% of the applied N fertilizers could be absorbed and incorporated into crops (Raun and Johnson, 1999).

2、Nitrogen Journey in Plants: From Uptake to Metabolism, Stress Response

Plants uptake and assimilate nitrogen from the soil in the form of nitrate, ammonium ions, and available amino acids from organic sources. Plant nitrate and ammonium transporters are responsible for nitrate and ammonium translocation from the soil into the roots.

3、Understanding Nitrogen Assimilation in Plants

Nitrogen assimilation is a critical process in plants, allowing them to convert absorbed nitrogen compounds into usable forms that support growth and metabolism.

4、Understanding Nitrogen Fixation in Plants

Since plants cannot absorb atmospheric nitrogen directly, they rely on fixed nitrogen from the soil. This dependence makes understanding nitrogen fixation critical for agriculture and ecosystem management. What Is Nitrogen Fixation?

microbial

The availability of N is a major growth-limiting factor for plants and it is significantly affected by the plant microbiome. Plants and microorganisms form complex interaction networks resulting in molecular signaling, nutrient exchange, and other distinct metabolic responses.

Nitrogen Journey in Plants: From Uptake to Metabolism, Stress

Plants uptake and assimilate nitrogen from the soil in the form of nitrate, ammonium ions, and available amino acids from organic sources. Plant nitrate and ammonium transporters are responsible for nitrate and ammonium translocation from the soil into the roots.

Nitrogen Fertilization I: The Nitrogen Balance

Fixation is mainly a biological process, and the most relevant organisms involved are Rhizobium bacteria that infect the roots of legumes. Organic N becomes inorganic through mineralization, and then inorganic N is absorbed by plants.

Nitrogen fertilization and soil nitrogen cycling: Unraveling the links

Here, we conducted a five-year field experiment and collected 54 soil samples from three 0–4 m boreholes across different treatments: control, N-addition (nitrogen fertilizer) and NPK-addition (combined application of nitrogen, phosphorus and potassium fertilizers) treatments.

Nitrogen uptake, assimilation and remobilization in plants: challenges

The use of nitrogen by plants involves several steps, including uptake, assimilation, translocation and, when the plant is ageing, recycling and remobilization. For crops, NUE has been defined as the grain yield per unit of nitrogen available from the soil, including nitrogen fertilizer.

(PDF) The Utilization and Roles of Nitrogen in Plants

After N is absorbed and utilized by plants, it plays important regulatory roles in phytohormones, microRNA (miRNA), root development and mycorrhizal symbiosis to cope with environmental...

The absorption of nitrogen fertilizer by plants does not qualify as nitrogen fixation; rather, it represents the bio-immobilization of nitrogen. Nitrogen fertilizers, which contain nitrogen compounds, are primarily used in agriculture to enhance crop yields and improve quality. Plants absorb nitrogen from the soil through their roots and convert it into usable forms, such as proteins, nucleic acids, and other organic compounds. This process involves the transformation and transport of nitrogen within the plant but does not alter its chemical properties.

Nitrogen Bio-Immobilization refers to the cyclical movement of nitrogen within ecosystems. When plants absorb nitrogen fertilizers, the nitrogen integrates into organic matter (e.g., proteins, fats, carbohydrates) via metabolic processes. These organic compounds accumulate in plants and are converted into energy through photosynthesis, fueling growth and development. After plant death, organic matter decomposes into inorganic nitrogen (e.g., ammonium, nitrate), which returns to the soil and can be reabsorbed by plants, completing the nitrogen cycle.

Within ecosystems, nitrogen bio-immobilization is a complex process:

1. Uptake and Assimilation: Plants absorb nitrogen from the soil and convert it into amino acids, nucleotides, and other biomolecules to support growth.
2. Decomposition and Recycling: Post-mortem, plant organic matter breaks down into inorganic nitrogen, which reenters the soil for reuse by plants.
3. Microbial Role: Organisms like bacteria and fungi facilitate nitrogen cycling by converting inorganic nitrogen into organic forms or vice versa.

Ecological Significance of Nitrogen Bio-Immobilization:

• Ecosystem Stability: Nitrogen is essential for life processes (e.g., protein synthesis, enzyme function). Its cycling maintains biodiversity and ecological balance.
• Material Cycling: Nitrogen interacts with carbon, phosphorus, and other elements to form organic and inorganic compounds, enabling nutrient transfer across organisms.
• Productivity: Adequate nitrogen supply boosts plant growth rates and biomass, enhancing ecosystem productivity.

Agricultural Practices for Efficient Nitrogen Use:

1. Rational Fertilization: Avoid overapplication of nitrogen fertilizers to prevent soil degradation and environmental pollution. Tailor dosage and timing to crop needs and soil conditions.
2. Organic Fertilizers: Replace synthetic fertilizers with organic matter (e.g., compost) to improve soil structure, micronutrient content, and long-term fertility.
3. Straw Incorporation: Return crop residues to fields to increase soil organic matter and reduce reliance on chemical inputs.
4. Soil Management: Monitor soil pH, nutrients, and erosion risks. Use practices like deep tillage or residue mulching to minimize nitrogen loss via runoff or wind erosion.

plant absorption of nitrogen fertilizers reflects nitrogen bio-immobilization, not fixation. This process is critical for ecological balance, material cycling, and agricultural productivity. Sustainable nitrogen management—through optimized fertilization, organic amendments, and soil conservation—ensures the long-term availability and efficiency of this vital resource.