The core dilemma facing modern agriculture lies in a tripartite challenge: achieving high crop yields and superior quality (which demands ample nutrition); contending with frequent abiotic stresses—such as drought, soil salinity, and extreme temperatures (which necessitates robust stress tolerance); and avoiding phytotoxicity resulting from the improper use of pesticides (which requires safety assurance). Traditional agrochemicals typically address only a single issue; biostimulants, however—leveraging their unique biological mechanisms and operating from the fundamental logic of plant metabolism—achieve an organic integration of nutritional support, stress tolerance, and safety-enhancing functions.
Biostimulants-Nutritional efficacy: the leap from“passive supply”to“active absorption”
Traditional fertilizers provide “raw materials”, while biostimulants provide “absorption capacity and transportation efficiency”.
1.The “architect” of root engineering: humic acid, seaweed extract and specific amino acids can stimulate root meristems and significantly increase root hair density and length. This is equivalent to expanding the “port” for nutrient absorption. Experiments show that after using mineral fulvic acid, the surface area of wheat roots can be increased by more than 30%, and the absorption rate of difficult-to-mobile nutrients such as phosphorus and zinc is greatly improved.
2.”Activation and chelator” of nutrients: Active groups such as carboxyl and phenolic hydroxyl groups in biostimulants can form soluble chelates with fixed trace elements such as calcium, iron, and zinc in the soil to prevent their precipitation and failure. At the same time, microbial biostimulants (such as Bacillus) can secrete organic acids and enzymes to convert ineffective phosphorus and potassium in the soil into available forms.
3.Metabolic “acceleration engine”: absorbed amino acids and small molecule peptides can directly participate in plant protein synthesis, saving energy. Research shows that foliar spraying of amino acid biostimulants can increase nitrate reductase activity by more than 50%, significantly accelerate nitrogen assimilation, and achieve “use less fertilizer and produce more grain.”
Biostimulants-Anti-stress effect: building a “physiological vaccine” for systemic defense
Biostimulants do not directly kill pathogenic bacteria or eliminate stress, but make the plants themselves stronger by “inducing resistance.”
1.Osmotic “reservoirs”: Under drought or salt stress, plants can become dehydrated. Biostimulants can induce plants to synthesize large amounts of compatible solutes such as proline, betaine, and trehalose. These substances can maintain cell turgor without interfering with normal metabolism. They are like storing “backup drinking water” for cells, helping plants to continue to survive in water-deficient environments.
2.The “fire brigade” of the antioxidant system: Adversity produces large amounts of reactive oxygen species (ROS) that attack cell membranes. Biostimulants (especially mannitol and fucoidan in seaweed extracts) can directly scavenge free radicals and activate the gene expression of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Experimental data show that when biostimulants are applied before low temperature stress, the malondialdehyde (membrane damage marker) content in pepper leaves can be reduced by more than 40%.
3.The “commander” of the signaling pathway: Specific oligosaccharides and microbial metabolites can simulate endogenous signals in plants (such as salicylic acid, jasmonic acid), activate system acquired resistance (SAR) or induce systemic resistance (ISR) in advance, so that plants are already in an “alert state” before heat waves and frosts come.
Biostimulants–The effect of“safety agent”: the“detoxification engineer”that resolves the risk of chemical hazards
The essence of pesticide damage (especially herbicide drift or residue) is that exogenous chemicals disrupt the normal hormone balance or metabolic pathways of plants. Biostimulants play a triple role here.
1.“Catalyst” of metabolic detoxification: Some biostimulants (such as glutathione, certain plant extracts) can induce the activity of cytochrome P450 monooxygenase and glutathione-S-transferase (GST) in plants. These are the core enzyme systems used by plants to degrade pesticides. Studies have shown that the application of specific amino acid combinations can accelerate the degradation of acetochlor residues in corn by 2-3 times.
2.“Stabilizer” of hormone balance: Sulfonylurea herbicides often inhibit acetolactate synthase (ALS), leading to stagnant plant growth. Brassinolides or specific small molecule peptides in biostimulants can bypass blocked metabolic nodes and restart cell division and elongation by regulating the synthesis and transport of auxin (IAA) and gibberellins, allowing crops to recover from phytotoxic stagnation.
3.“Protective shield” for isolation and competition: New polymer biostimulants (such as polyglutamic acid, modified chitosan) can form a protective film on the leaf surface to reduce the absorption and penetration of pesticides. At the same time, its active groups can form non-covalent bonds with pesticide molecules (such as hydrogen bonds, hydrophobic interactions), reducing the concentration of free pesticides, thereby reducing direct toxicity to crops.
Biostimulants–Case Studies and Selection Recommendations
| Category | Representative Products | Nutritional Benefits | Stress Resistance Benefits | Safeners / Other Highlights |
| Amino Acids / Peptides | Protein Hydrolysates, Enzymatically Hydrolyzed Feather Meal | ★★★ (Direct nitrogen source; chelates trace elements) | ★★★ (Proline and similar compounds regulate osmotic pressure; repair tissue damage) | ★ (Mitigates mild phytotoxicity; stimulates growth initiation) |
| Humic Acids / Fulvic Acids | Mineral-derived Fulvic Acid, Lignite Extracts | ★★ (Mobilizes soil nutrients; improves fertilizer efficiency) | ★★ (Regulates stomatal function; enhances drought and cold tolerance) | – |
| Microorganisms | Trichoderma spp., Rhizobium spp. | ★★★ (Nitrogen fixation; phosphorus solubilization; hormone production) | ★★ (Induces systemic resistance; enhances disease and salinity tolerance) | – |
| Polysaccharides / Plant-derived | Seaweed Extracts, Pollen Polysaccharides | ★ (Provides bioactive substances) | ★★★ (Activates antioxidant systems; enhances tolerance to high and low temperatures) | – |
| Inorganic / Chemical | Phosphites, Silicates | ★ (Supplements beneficial elements, e.g., silicon) | ★★ (Strengthens cell walls; enhances disease and stress resistance) | – |
| Novel Carriers | Poly-gamma-glutamic Acid (γ-PGA) Nanomicelles | ★ (Promotes growth intrinsically) | – | ★★★ (Encapsulates pesticides; enables pH-responsive release; reduces toxicity) |
The Integrative Effect: A Synergistic Triad
The true brilliance of biostimulants lies in the fact that their three-fold functions are not merely additive; rather, they are mutually causative and synergistically amplified. A robust root system (nutritional efficacy) naturally facilitates superior water uptake and drought resistance (stress-tolerance efficacy); similarly, a plant with vigorous metabolism and active enzymatic systems (combining nutritional and stress-tolerance benefits) naturally possesses a heightened capacity for pesticide degradation (safener efficacy). For instance, following the application of alginate oligosaccharides, plant leaves become greener (nutritional improvement), while proline levels rise (enhanced stress tolerance), and the tolerance threshold against subsequent herbicide applications increases significantly (safener action).
Consequently, the essence of biostimulants is “empowerment,” not “substitution.” By precisely modulating the plant’s endogenous physiological metabolism, they enable crops to absorb nutrients with high efficiency while simultaneously establishing a multi-dimensional defense network against environmental stressors—thereby acquiring the proactive capacity to neutralize exogenous chemical stresses (such as phytotoxicity). This philosophy of “preventing disease before it strikes”—a form of biological wisdom—constitutes an indispensable core technology within the realm of green and sustainable agriculture.