In modern agricultural production, amino acids are widely used in all stages of crop cultivation as efficient and environmentally friendly plant growth regulators and nutrient supplements. Glutamate, lysine, and proline are three representative agricultural amino acids that play important roles in promoting crop growth, enhancing stress resistance, and improving quality. However, due to differences in molecular structure and physiological function, their specific application scenarios and methods of use differ significantly.
Common Functions of Agricultural Glutamate, Lysine, and Proline
Although the physiological functions of these three amino acids differ, they share the following common functions in agricultural applications:
1. Supplementing Plant Nutrition and Promoting Growth and Development
Glutamate, lysine, and proline are all important raw materials for protein synthesis in plants. They can be directly absorbed and utilized by crops through foliar spraying or root application, participating in cell structure construction and enzyme synthesis, thereby promoting plant growth and increasing biomass. For example, when applied during the seedling stage, all three can accelerate root development and leaf expansion, laying the foundation for subsequent growth.
2. Enhance Crop Stress Resistance
All three types of amino acids can enhance crops' adaptability to adverse conditions such as drought, salinity, and low temperature by regulating osmotic balance and activating antioxidant systems. When crops encounter abiotic stress, the content of free amino acids in the plant increases significantly, and exogenous supplementation can further enhance the water-retention capacity and membrane stability of cells, reducing cell damage caused by stress.
3. Improve Crop Quality and Increase Yield
All three can improve crop yield and quality by participating in nitrogen metabolism and promoting the accumulation of photosynthetic products. For example, application during the fruit enlargement stage can increase the content of soluble sugars and vitamins in the fruit, improving taste and nutritional value; at the same time, it promotes the translocation of nutrients to harvested organs, increasing thousand-grain weight or single fruit weight.
4. Improving Fertilizer Utilization
As organic nitrogen sources, glutamate, lysine, and proline can be used in combination with inorganic fertilizers. By activating soil microorganisms and promoting root absorption of nitrogen, phosphorus, potassium, and other elements, they reduce fertilizer loss, improve fertilizer utilization, and lower the risk of environmental pollution.
Differences in the Functions of Agricultural Glutamate, Lysine, and Proline
1. The Core Function of Glutamate
Glutamate is a key intermediate product of nitrogen metabolism in plants, and its function focuses more on "metabolic regulation" and "nutrient transformation":
(1) Participation in Nitrogen Metabolism and Amino Acid Synthesis
Glutamate is a precursor to the synthesis of various amino acids (such as glutamine, proline, and arginine) in plants. Through transamination, it provides amino groups for other amino acids and is a core hub for nitrogen assimilation and distribution. Therefore, applying glutamate during the growth stages when crops have high nitrogen requirements (such as the vegetative growth stage) can significantly promote nitrogen absorption and utilization.
(2) Promoting Chlorophyll Synthesis and Photosynthesis
Glutamate is a component of the porphyrin ring in chlorophyll. Exogenous supplementation can accelerate chlorophyll synthesis and increase the photosynthetic rate of leaves. When crop leaves turn yellow or photosynthetic efficiency declines (such as during prolonged cloudy days or premature senescence), spraying glutamate can quickly alleviate symptoms and restore leaf function.
(3) Regulating Stomatal Opening and Closure and Water Balance
Glutamate can regulate stomatal opening and closing by affecting the osmotic pressure of guard cells, reducing water transpiration under drought conditions while ensuring CO₂ supply, thus balancing the relationship between water retention and photosynthesis. This effect is particularly important in crop cultivation in arid regions.
2. The Core Role of Lysine
Lysine is an essential amino acid in plants (essential for humans but synthesizable by plants). Its role focuses more on "physiological activity regulation" and "quality improvement":
(1) Activating the plant defense system and enhancing disease resistance
Lysine can be converted into substances with antibacterial activity (such as cadaverine, a product of lysine decarboxylase) within plants, inhibiting the growth and reproduction of pathogens; simultaneously, it can induce crops to produce pathogenesis-related proteins (PR proteins), enhancing resistance to fungal and bacterial diseases. Therefore, applying lysine during periods of high disease incidence (such as the middle and late stages of crop growth) can reduce disease occurrence.
(2) Promoting reproductive growth and improving fruit quality
Lysine has a special regulatory effect on flowering and fruit setting in crops, promoting pollen development, increasing pollination rate, and accelerating the accumulation of protein and essential amino acids in fruits. Applying lysine during the flowering and fruit development stages of fruit trees and vegetables can significantly improve fruit setting rate, increase the content of essential amino acids such as lysine in fruits, and enhance nutritional value.
(3) Alleviating Heavy Metal Stress
Lysine can bind with heavy metal ions (such as lead and cadmium) in the soil through chelation, reducing their bioavailability and decreasing crop absorption of heavy metals; simultaneously, it regulates the activity of heavy metal detoxification enzymes in the plant, mitigating the toxicity of heavy metals to cells. This effect makes it valuable for remedial planting in heavy metal-contaminated soils.
3. The Core Role of Proline
Proline is one of the most important osmotic regulators in plants, with its role focusing on "stress protection" and "cell repair":
(1) Osmotic Protection under Strong Stress
In extreme stresses such as drought and salinity, proline is the most abundant free amino acid in plants. Its molecular structure has strong hydrophilicity, which can reduce osmotic potential by increasing cell sap concentration, reducing water loss, and maintaining cell turgor pressure. Therefore, applying proline before or during stress has a much better stress-resistance effect than the other two types of amino acids.
(2) Stabilizing the Structure of Biological Macromolecules
Proline can bind to biological macromolecules such as proteins and nucleic acids, maintaining the stability of their spatial structure and preventing protein denaturation and enzyme activity loss under stress conditions. For example, under low-temperature stress, proline can protect cell membranes and enzyme systems, maintaining normal metabolic activity.
(3) Antioxidant and Free Radical Scavenging
Proline can directly scavenge reactive oxygen species (such as hydroxyl radicals and hydrogen peroxide) generated under stress, or reduce oxidative damage by enhancing the activity of antioxidant enzymes such as superoxide dismutase (SOD) and peroxidase (POD). This effect is particularly prominent when crops are subjected to drought and high-temperature stress.
Usage Methods of Agricultural Glutamate, Lysine, and Proline
1. Applicable Crops and Growth Stages
(1) Glutamate
Applicable Crops: All kinds of crops (especially leafy vegetables and cereals).
Optimal Time: Seedling stage (promotes vegetative growth), leaf yellowing stage (restores photosynthetic function), peak nitrogen demand stage (such as wheat jointing stage, rice tillering stage).
(2) Lysine
Applicable crops: Fruit trees, vegetables, legumes (crops requiring improved quality and disease resistance).
Optimal time: Flowering period (improves fruit set rate), fruit enlargement period (improves quality), high disease incidence period (enhances disease resistance).
(3) Proline
Applicable crops: Drought-resistant crops (such as corn and cotton), saline-alkali soil crops, and open-field crops susceptible to adverse conditions.
Optimal time: 1-3 days before adverse stress (such as before drought or cold wave), during stress (alleviates damage), and during post-stress recovery period (promotes repair).
2. Application methods and concentrations
(1) Foliar spraying
Glutamate: Concentration is usually 0.2%-0.5%, dosage is 50-100 grams per acre, diluted in 30-50 kg of water, sprayed evenly on both sides of the leaves, once every 7-10 days, for 2-3 consecutive times.
Lysine: Concentration 0.1%-0.3%, dosage 30-50 grams per mu (667 square meters), diluted in 30 kg of water. Focus on spraying the flowers and fruits, applying 2-3 times from flowering to fruit ripening.
Proline: Concentration 0.1%-0.2%, dosage 20-40 grams per mu (667 square meters), diluted in 30 kg of water. Spray before or during abiotic stress. In severe stress, the interval can be shortened to 5 days, applied twice consecutively.
(2) Root Application
Glutamate: Can be mixed with organic or chemical fertilizers, dosage 100-200 grams per mu (667 square meters), applied with irrigation water or furrow application. Suitable for crop seedlings or when soil nitrogen is insufficient.
Lysine: Often used in combination with compound fertilizers, dosage 50-100 grams per mu (667 square meters). Apply during fruit enlargement along with irrigation to promote nutrient transport to the fruit.
Proline: Apply to roots at a concentration of 0.3%-0.5%, using 50-100 grams per mu (approximately 0.067 hectares). Suitable for improving saline-alkali land or for root irrigation before sowing crops in arid regions, enhancing root resistance.
(3) Seed Treatment
Lysine and proline can be used for seed soaking at a concentration of 0.1%-0.2%. Soaking time should be adjusted according to crop type (e.g., 6-8 hours for wheat, 8-12 hours for corn). This can improve seed germination rate and seedling resistance. Glutamate has a weaker effect and is rarely used alone.
Precautions
1. Combined Use
The three amino acids can be mixed according to crop needs. For example, during the seedling stage, glutamate should be the main component, combined with proline to enhance resistance; during the fruiting stage, lysine should be the main component, combined with glutamate to promote nutrient conversion. However, concentration control is necessary to avoid excessive total amino acid concentration leading to fertilizer damage.
2. Avoid Mixing with Incompatible Substances
Do not mix directly with strongly alkaline pesticides (such as Bordeaux mixture or lime sulfur) or high-concentration fertilizers, as this may damage the amino acid structure. It is recommended to use alone or in combination with neutral or weakly acidic substances.
3. Spraying Time
Follicular spraying should be done on sunny mornings or evenings, avoiding periods of high temperature and strong sunlight to reduce evaporation loss and leaf burn. Do not spray on rainy days; if rain occurs within 6 hours of spraying, re-spray.
4. Storage Conditions
Amino acid products are hygroscopic and should be sealed and stored in a cool, dry place, avoiding direct sunlight and high temperatures to prevent degradation of the active ingredients.
