For a long time, it was a widely accepted notion that plants could not directly absorb organic forms of nitrogen, such as amino acids, and required mineralization to convert them into simpler inorganic forms. However, recent studies have challenged this belief, showing that in many soil systems, plants absorb a significant proportion of their nitrogen from amino acids, especially in nitrogen-deficient soils where their role becomes indispensable.
The Multifunctional Benefits of Amino Acids
Amino acids are not just a source of organic nitrogen for plants; they also play a variety of roles, including protein synthesis and regulation of plant growth. Here's a look at how different types of amino acids contribute to plant physiology:
L-Alanine: Enhances chlorophyll synthesis, regulates stomatal opening, and combats pathogens.
L-Arginine: Boosts root development and acts as a precursor for polyamine synthesis, improving salt stress tolerance.
L-Aspartic Acid: Promotes seed germination and provides a nitrogen source during stressful periods.
L-Cysteine: Maintains cellular functions and serves as an antioxidant for sulfur.
L-Glutamic Acid: Reduces nitrate levels and promotes photosynthesis in leaves.
L-Glycine: Uniquely affects photosynthesis and increases sugar content.
L-Histidine: Regulates stomatal opening and provides a precursor for carbon skeleton hormones.
L-Isoleucine and Leucine: Improve resistance to salt stress and increase pollen viability.
L-Lysine: Enhances chlorophyll synthesis and improves drought resistance.
L-Methionine: A precursor for polyamine synthesis.
L-Phenylalanine: Promotes lignin synthesis and is a precursor for anthocyanins.
L-Proline: Increases tolerance to osmotic stress, enhances stress resistance, and boosts pollen viability.
L-Serine: Participates in cell differentiation and promotes germination.
L-Threonine: Improves tolerance and defends against pests and diseases.
L-Tryptophan: A precursor for the synthesis of auxin indole acetic acid, enhancing the synthesis of aromatic compounds.
L-Tyrosine: Increases drought resistance and improves pollen germination.
L-Valine: Improves seed germination rates and enhances crop flavor.
These amino acids also exhibit synergistic effects, such as promoting chlorophyll production, plant hormone formation, root development, seed germination, flowering and fruiting, and improving fruit flavor.
Amino Acids, Peptides, and Proteins
Amino acids are the building blocks of proteins and are easily absorbed by plants. Oligopeptides, composed of 2 to 10 amino acids, are also known as small peptides. Polypeptides consist of 11 to 50 amino acids and have relatively larger molecular weights. Proteins, made up of more than 50 amino acids, cannot be directly absorbed by plants.
Application Methods for Amino Acid Fertilizers
The application methods for amino acid fertilizers include drip irrigation, flushing, and foliar spraying. They are best used as top dressing rather than as a base fertilizer. When choosing fertilizers, small peptides can be selected for resistance to adverse environments and to enhance the stress resistance of crops, while regular amino acid fertilizers are more suitable for improving fertilizer efficiency. When using amino acid fertilizers, it is important to apply them promptly, as they are prone to microbial decomposition once exposed.
The Importance of Amino Acid Fertilizers in Agriculture
The exogenous application of amino acid-based fertilizers is essential for leveraging the physiological regulatory functions of plants, increasing yield, and enhancing stress resistance. These fertilizers are a vital component in modern agricultural practices, ensuring that plants receive the necessary nutrients in a form that is readily available and beneficial for their growth and development.
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