How Biostimulants Improve Plant Stress Tolerance

Biostimulants are gaining popularity as effective and sustainable agronomic tools to boost yields. But biostimulants go far beyond just being a fertilizer alternative or complement: these products and substances can also play a critical role in improving plant stress tolerance.
Stress is imposed on plants from multiple sources. This includes abiotic stresses—things like drought, extreme heat, and salinity—as well as biotic stress from other organisms like pathogenic bacteria, viruses, fungi, parasites, and insects.
By stimulating desirable biological processes, biostimulants can help plants withstand and adapt to these stresses. This blog will explore how different biostimulants improve plant stress tolerance and how you can put them into action effectively.  


Biostimulants are natural or synthetic substances that, when applied to plants or soil, stimulate biological processes to enhance plant growth, yield, and quality. They are not fertilizers, which provide the essential nutrients for plant growth, but they do improve a plant’s ability to access and use those nutrients by stimulating beneficial various physiological and metabolic processes. Biostimulants also activate processes that better enable plants to withstand environmental stresses.
Biostimulants can be made from various sources, such as plant extracts, seaweed, humic and fulvic acids, amino acids, enzymes, or beneficial microbes. Our blog on plant biostimulants takes a deeper dive into what they are, how they work, and how to incorporate them into your farm, hydroponic system, greenhouse, or garden.


So, why prioritize building plant stress tolerance with biostimulants? The many potential benefits of using biostimulants include:
  • Increased yield and quality: Stress-resistant plants are more productive. Rather than directing precious energy towards fending off pests or withstanding a prolonged heatwave, stress-tolerant plants are naturally higher-yielding plants. Some biostimulants, like silicic acid, can also increase quality traits such as flavor and aroma.
  • Improved climate resilience: Plant stressors like heat, drought, and infestation are increasing in frequency and intensity as global temperatures rise. Biostimulants equip plants with the ability to thrive in more hostile growing conditions.
  • Reduced input costs: By optimizing nutrient availability and plant resistance responses, biostimulants can help plants thrive while reducing reliance on expensive—and environmentally damaging—synthetic fertilizers and pesticides.
  • Sustainable growing practices: Biostimulants are compatible with organic and conventional farming practices, and many are produced sustainably with a relatively low impact. Microbial inoculants are, theoretically, in infinite supply. Others, like protein hydrolysates, are agricultural by-products that previously went to waste. And unlike chemical pesticides, using biostimulants to improve plant stress tolerance helps build soil diversity rather than destroy it.


There is still so much we don’t understand about the mechanisms through which biostimulants affect plant stress tolerance. Although the exact modes of action are unclear, biostimulants have repeatedly demonstrated an ability to activate certain plant responses to improve stress tolerance from both abiotic and biotic factors.


Water stress is a leading challenge for growers around the world. When water availability is reduced, plant photosynthetic activities are negatively impacted, which often degrades crop quality and overall yields.
There is excellent research demonstrating that certain biostimulants can aid in the accumulation of osmotically active compounds to help plants manage water status in periods of drought. Biostimulants also improve overall water efficiency by reducing transpiration rates and by building healthy, diverse soils—which are better at retaining water.


Most plants are quite sensitive to saline stress: any overabundance of water-soluble salts in soil and irrigation water reduces plant growth and overall vitality. High salt concentrations reduce water absorption through plant roots. By improving water use efficiency to offset the effects of drought, biostimulants can similarly increase plant tolerance to saline stress. Protein hydrolysates and microbial biostimulants have been shown to improve the yields of crops grown in high-salinity environments.


Temperature stress can profoundly affect crop production, whether through early or late-season frosts or prolonged summer heat waves.  
Low temperatures are particularly concerning for early transplants or any crop with early flowering. Amending crops with biostimulants like silicon, amino acids, and microbial inoculants can improve plant cold tolerance by encouraging the accumulation of cryoprotectants—compounds that prevent cell or tissue damage from freezing—and by activating membrane repair systems. 
High temperatures also damage plant cells and increase transpiration rates, which exacerbates water stress. Biostimulants can improve water absorption capacity, water use efficiency, and cell membrane protection. Additionally, recent trials of Impello’s Continuμm™ microbial inoculant demonstrated a 10% reduction in sunburn on desert-grown bell pepper crops, increasing marketable yields. These critical adaptations are becoming ever more important as many of the world’s growing regions face the dual threat of hotter and drier growing seasons.


Biostimulants can enhance the absorption and translocation of nutrients from the rhizosphere to plants, as well as improve the efficiency of nutrient use within the plant. Optimizing nutrient availability and efficiency preserves energy, and plants to initiate stress responses more effectively.


Certain biostimulants initiate a plant defense response to pests and pathogens in a process known as induced resistance. For example, exposure to beneficial microbes found in high-quality microbial inoculants can mimic the molecular pathways that react to infestation or infection. Intentionally triggering a plant’s resistance response mechanisms arm it with the ability to respond to future threats. 


If you’re looking to arm your crops with some added resilience, these are the best-understood and most effective biostimulants for enhancing plant stress tolerance.


Used by farmers for hundreds of years, seaweed extracts can improve plant tolerance to salinity, heat, and drought. They contain alginates and other polysaccharides that enhance soil structure and water-holding capacity.  
Seaweed extracts are also an excellent source of plant hormones that stimulate root growth and increase nutrient uptake. Most seaweed extract products are agal based and applied as a foliar treatment.


Humic substances, particularly humic acid and fulvic acid, are potent biostimulants. They are created naturally through the decomposition of organic matter. Humic acid and fulvic acid can be amended to growing mediums to stimulate the growth and development of plant roots. They can add plant stress tolerance by improving the absorption of nutrients and water.


Protein hydrolysates consist of various substances, including amino acids, peptides, and polypeptides, which are obtained by breaking down proteins from complex biological sources. Animal sources of protein hydrolysate include bone meal, feather meal, fish meal, and other agricultural by-products. Other sources include legumes, soybeans, corn, and wheat.  

Protein hydrolysates can enhance crop growth and their ability to withstand environmental stressors. Lumina™ is Impello’s proprietary, certified-organic protein hydrolysate biostimulant. Sourced from molasses and shrimp protein hydrolysate, Lumina™ contains bioavailable nitrogen, polypeptides, and amino acids, which all serve to improve crop tolerance to abiotic stress and address nutrient deficiencies. Protein hydrolysate solutions like Lumina™ can also have a synergistic effect with beneficial microbes.


Inoculating your soil and plants with microbial microbes is an effective way to improve the stress tolerance of your plants. 
Certain bacteria have evolved to thrive in adverse environmental conditions. They can engage in symbiotic relationships with plants to help them do the same. Microbial inoculants, like Impello’s Continuμm™, will help produce growth-promoting compounds, optimize nutrient availability, improve water absorption, and can induce systemic resistance responses to help plants cope with extreme temperatures, drought, salinity, and disease.


Although almost all soils are rich in silicon, very little is available to plants. And, without sufficient bioavailable silicon, plants become structurally weaker and more susceptible to biotic and abiotic stresses.  

Monosilicic acid—the only plant-available form of silicon—can be used as a biostimulant to promote resilience to heat, cold, and drought. It also acts as a pesticide, deterring the growth of detrimental insect populations and pathogenic bacteria.  

Stabilized monosilicic acid products, like Impello’s Dune™, are easily applied as a foliar spray, through hydroponic fertigation systems, or as a soil amendment. 

Impello Dune Biostimulant

Click here to experience the benefits of natural and sustainable plant growth!


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De Saeger, J., Van Praet, S., Vereecke, D., Park, J., Jacques, S., Han, T., & Depuydt, S. (2020). Toward the molecular understanding of the action mechanism of Ascophyllum nodosum extracts on plants. Journal of Applied Phycology, 32(1), 573–597. 

Franzoni, G., Cocetta, G., Prinsi, B., Ferrante, A., & Espen, L. (2022b). Biostimulants on Crops: Their Impact under Abiotic Stress Conditions. Horticulturae, 8(3), 189.

Halpern, M., Bar-Tal, A., Ofek, M., Minz, D., Müller, T., & Yermiyahu, U. (2015). The Use of Biostimulants for Enhancing Nutrient Uptake. Elsevier EBooks, 141–174.

Khan, W., Rayirath, U. P., Subramanian, S., Jithesh, M. N., Rayorath, P., Hodges, Æ. D. M., Critchley, A. T., Craigie, J. S., Norrie, J., & Prithiviraj, B. (2009). Seaweed Extracts as Biostimulants of Plant Growth and Development. Journal of Plant Growth Regulation, 28(4), 386–399. 

Miceli, A., Moncada, A., & Vetrano, F. (2021). Use of Microbial Biostimulants to Increase the Salinity Tolerance of Vegetable Transplants. Agronomy, 11(6), 1143.

Van Oosten, M. J., Pepe, O., De Pascale, S., Silletti, S., & Maggio, A. (2017). The role of biostimulants and bioeffectors as alleviators of abiotic stress in crop plants. Chemical and Biological Technologies in Agriculture, 4(1).

Yu, Y., Gui, Y., Li, Z., Jiang, C., Guo, J., & Niu, D. (2022). Induced Systemic Resistance for Improving Plant Immunity by Beneficial Microbes. Plants, 11(3), 386.

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