Chitosan, chitosan oligosaccharides, and Alginate oligosaccharide are all biostimulants and plant immune inducers that have attracted much attention in green agriculture in recent years. Below I will provide a detailed comparison of their applications and characteristics in agriculture.
Core Summary
| Characteristics | Chitosan | Chitosan oligosaccharides | Alginate oligosaccharide |
| Sources | Crustacean shells, fungal cell walls | Enzymatic or acid hydrolysis products of chitosan | Extracted degradation products of brown algae (such as kelp and sargassum) |
| Molecular weight | High (100,000-1,000,000 Daltons) | Low (usually <3,000 Daltons) | Low (usually <3,000 Daltons) |
| Water solubility | Poor (soluble in dilute acid solution) | Good (directly soluble in water) | Excellent (directly soluble in water) |
| Core mechanism of action | Physical barrier + slow-release induction | Signaling molecule + direct induction | Nutrient supply + signal regulation |
| Main application features | Excellent film-forming properties, slow-release effect, soil improvement | High activity, fast-acting, broad-spectrum immune activation | Comprehensive nutrition, root growth and seedling growth, strong stress resistance |
| Application cost | Relatively low | High | Usually the highest |
Introduction and Application
1.Chitosan
Chitosan, derived from the shells of crustaceans like shrimp and crab, or from the cell walls of fungi, is a natural cationic alkaline polysaccharide. Due to its biocompatibility, biodegradability, non-toxicity, and unique bioactivity, it plays an increasingly important role in green agriculture and is known as an excellent “plant immune activator” and “soil conditioner.”
Agricultural Applications:
Seed Treatment: Forms a protective film on the seed surface that retains water, allows air to pass through, and stimulates germination, increasing germination rates.
Foliar Spray: Forms a thin film on the leaf surface that can:
Physical Barrier: Impedes pathogen infection to a certain extent.
Induced Resistance: Slowly degrades and continuously stimulates the plant, activating systemic resistance.
Soil Conditioner:
Inhibits harmful fungi (such as Fusarium and Rhizoctonia) in the soil.
Improve soil aggregate structure and promote the growth of beneficial soil microorganisms (such as actinomycetes).
Can be used as a carrier for slow-release fertilizers or pesticides.
Fruit and Vegetable Preservation: Post-harvest film coating reduces water evaporation, inhibits spoilage bacteria, and extends shelf life.
Advantages: Widely available, low cost, and film-forming properties, offering unique advantages in soil conditioning and slow-release applications.
Disadvantages: Poor water solubility, needs to be dissolved in dilute acid (such as acetic acid) before use, relatively low biological activity, and slow plant absorption and response.
2.Chitosan oligosaccharide
Chitosan oligosaccharides are an upgraded version of chitosan, derived from chitosan through enzymatic or chemical degradation. They are typically composed of 2-10 monosaccharides. Their smaller molecular weight, excellent water solubility, and higher biological activity make them more precise and effective as “signaling molecules” and “plant vaccines” in agriculture.
Agricultural Applications:
Highly Effective Plant Immune Activator (Core Application):
Recognized by receptors on plant cell membranes, this “alarm bell” rapidly activates the plant’s defense system, producing disease-fighting substances (such as phytoalexins, phenolics, and reactive oxygen species), effectively combating fungal, bacterial, and viral diseases. This disease-fighting mechanism is known as the “plant vaccine” effect.
Growth Promotion:
Activates the metabolism of growth-related hormones (such as auxin) in plants, promoting root development and strengthening plants.
Quality Improvement: Increases sugar content and vitamin content in crops.
Insecticide Induction: Certain substances produced by this agent have a repellent or toxic effect on pests.
Advantages: High water solubility, high biological activity, low dosage (usually ppm level), rapid onset of action, and a broad-spectrum immune inducer.
Disadvantages: Requires complex production processes, is more expensive than chitosan, and has a shorter duration of effectiveness in soil.
3.Alginate oligosaccharide
Alginate oligosaccharides are small molecular weight fragments of alginate extracted from brown algae (such as kelp and sargassum) through physical, chemical, or enzymatic degradation. They inherit many of the advantages of seaweed fertilizers, while exhibiting more efficient and precise bioactivity than traditional seaweed fertilizers due to their small size and specific signaling properties
Agricultural Applications:
Excellent Growth Promoter:
Rich in fucoidan, alginic acid, mannitol, iodine, potassium, and various trace elements, it provides abundant nutrients for plants.
Strongly promotes root development, manifesting as a “root burst” effect, enhancing crop absorption capacity.
Enhanced Stress Resistance:
Significantly improves plant resistance to abiotic stresses such as drought, salinity, low temperature, and high temperature. It induces the production of osmotic regulators such as proline and soluble sugars, maintaining normal cellular function.
Induces Disease Resistance:
Similar to chitosan oligosaccharides, it can act as a signaling molecule to induce systemic resistance in plants, but its signaling pathways and the anti-disease substances it produces may differ from those of chitosan oligosaccharides.
Improves Soil Microbiome: Promotes the proliferation of beneficial bacteria in the soil.
Advantages: Comprehensive nutrition, extremely significant growth-promoting effects, outstanding performance in stress resistance (especially drought and salt tolerance), and high safety.
Disadvantages: Raw material and production costs are usually the highest, and research on the specificity and strength of inducing disease resistance may be slightly less than that of chitosan oligosaccharides.
Comprehensive comparison and how to choose
| Application Objectives | Recommendation Priority | Reasoning |
| Disease Prevention (as a plant vaccine) | Chitosan oligosaccharide > Alginate oligosaccharide ≈ Chitosan | Chitosan oligosaccharides are the most intensively studied signaling molecules, possessing the strongest and most specific immune-activating abilities and the fastest effectiveness. |
| Growth Promotion and Root Strengthening | Alginate oligosaccharide > Chitosan oligosaccharide > Chitosan | Alginate oligosaccharides contain inherent nutrients, and their root-promoting and seedling-strengthening effects are often the most immediate and powerful. Chitosan oligosaccharides can also effectively promote growth by regulating endogenous hormones. |
| Drought and Salt-Alkali Resistance | Alginate oligosaccharide > Chitosan oligosaccharide > Chitosan | Alginate oligosaccharides have demonstrated remarkable research and practical results in enhancing crop stress resistance, which is related to the habitat of their source plants (seaweed). |
| Soil Improvement and Disinfection | Chitosan > Alginate oligosaccharide | Chitosan has a large molecular weight and a long persistence in soil, effectively inhibiting soil-borne pathogens and improving soil structure. |
| Seed Treatment/Fruit and Vegetable Preservation | Chitosan > Chitosan oligosaccharide | Chitosan’s film-forming properties are a unique advantage, making it ideal for coatings and film-coatings. |
| Cost Considerations | Chitosan > Chitosan oligosaccharide > Alginate oligosaccharide | Chitosan has the most mature raw materials and processing technology, resulting in the lowest cost, making it suitable for large-scale, basic applications. |
Actual use
Combination: Combining any of the three or any two of them can create synergistic effects. For example, chitosan oligosaccharides quickly boost immunity, Alginate oligosaccharides provide nutrition and stress resistance, and chitosan provides long-term root protection in the soil.
Combination with beneficial microorganisms: They can act as prebiotics, promoting the colonization and function of beneficial bacteria such as arbuscular mycorrhizal fungi and Bacillus subtilis.
Reducing and increasing synergy with chemical pesticides and fertilizers: As green inputs, reducing the use of chemical pesticides and fertilizers is a key approach to achieving sustainable agricultural development.
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