The biostimulant industry has grown rapidly over the past decade. With that growth has come a proliferation of products, claims, and marketing language that can make it genuinely difficult for agronomists and growers to evaluate what they are actually buying.
The concept of mode of action (MOA) is central to this evaluation. A clearly defined, scientifically validated MOA is the difference between a product you can rely on and one you are essentially gambling on. Yet precise MOA claims remain rare across the industry.
This article explains what mode of action means for biostimulants, why it is harder to establish than it sounds, and how the PSI Technology platform at Brandon Bioscience establishes MOA across its product range.
What Mode of Action Means
In simple terms, mode of action describes the specific biological mechanism by which a substance produces its observed effect in a plant. It is not enough to say a product ‘improves stress tolerance.’ A validated MOA tells you which genes are involved, which proteins they encode, which biochemical pathways are activated, and how those changes translate into the agronomic outcome you observe.
This level of mechanistic detail requires multiple layers of investigation: molecular (gene expression), biochemical (enzyme activity, metabolite levels), physiological (water content, ion balance), phenotypic (root and shoot development, fruit set), and field performance (marketable yield, quality markers). Working through all five layers takes years of research. But it is what allows a product to be genuinely next-generation rather than simply next in line.
Why MOA Is Difficult to Establish for Biostimulants
Biostimulants derived from natural materials such as seaweed extracts are chemically complex. They contain a wide variety of bioactive molecules, including complex carbohydrates, polysaccharides, polyphenols, amino acids, and minerals, whose individual and combined effects on plant biology are not fully characterised in the scientific literature.
This complexity is part of what makes them effective. Broad-spectrum bioactivity arising from multiple active compounds is a genuine advantage over single-molecule products. But it also makes it harder to attribute specific effects to specific molecules.
The approach Brandon Bioscience takes is to characterise the extract as a whole, understand its molecular profile in detail, and then link specific compositional features to specific biological outcomes. Research comparing two Ascophyllum nodosum extracts with different manufacturing processes showed that the aqueous extract, with higher concentrations of bioactive carbohydrates including fucoidan and laminarin, activated a different set of gene expression changes than the alkaline extract. The correlation between carbohydrate content and gene activity was measurable and consistent. That is the foundation for MOA attribution.
Case Study: SEALICIT and Pod Shatter
SEALICIT with PSI 759 Precision Technology provides one of the clearest examples of a fully validated MOA in the biostimulant industry.
The challenge: pod shatter in oilseed rape (OSR) and soybean causes average annual seed losses of 15-25% for growers. Pod shattering is controlled by a specific developmental pathway in the pod’s dehiscence zone, the region where the pod splits open at maturity.
The MOA: SEALICIT downregulates INDEHISCENT (IND), the master regulator gene responsible for pod opening. It also dysregulates the FRUITFUL (FUL) and REPLUMLESS (RPL) genes and disrupts local auxin homeostasis in the dehiscence zone. The combined effect is to increase lignin content in the replum, strengthen pod structural integrity, and delay the developmental signal that triggers pod splitting.
The outcome: in independent field trials across five OSR varieties, SEALICIT increased pod shattering resistance across all varieties, measured by a standardised Random Impact Test (RIT). The IND gene downregulation was directly confirmed by PCR analysis, and every batch of SEALICIT is bio-assayed before release to confirm consistent IND downregulation.
This is what a validated MOA looks like in practice: a specific gene, a specific biological pathway, a measurable agronomic outcome, and a quality control system built around the molecular marker itself.
Case Study: BLOCSAL and Salinity Tolerance
BLOCSAL with PSI 475 Precision Technology offers a second example, this time in the context of abiotic stress tolerance.
The mechanism involves three interconnected pathways. First, upregulation of sodium transporter genes (SOS1, HKT1, NHX1) restricts sodium movement from roots to younger shoot tissue, reducing ion toxicity in the most photosynthetically active parts of the plant. Second, potassium uptake is promoted in root tissue, restoring the K+/Na+ ratio that governs osmotic balance and enzyme function. Third, osmolyte production is stimulated, with proline accumulation increasing by 42% in trials, building cellular water retention capacity.
The outcome: 23% average marketable yield increase across tomato, pepper, and table grape in saline irrigation trials, with a 94% win rate. In a separate transcriptome study, yield uplift in stressed tomatoes reached 48%, closing the gap to within 3% of unstressed controls.
Every element of this chain, from gene expression to biochemical change to agronomic outcome, has been independently validated across two peer-reviewed publications.
What This Means for Growers and Agronomists
A validated MOA means a predictable product. When you understand exactly how a product works, you can make informed decisions about when to apply it, at what growth stage, under what conditions, and what to expect. It also means you can integrate it intelligently into a broader crop programme rather than applying it speculatively.
It means the product has been stress-tested through the scientific process. Peer-reviewed publication requires independent expert scrutiny of methodology, data quality, and conclusions. Brandon Bioscience ensures each product is brought to market with credibility through publication of peer- reviewed research and extensive trial data.
And it means the regulatory pathway is clear. MOA validation is the backbone of the technical dossier required for EU FPR claims, CE marking that can demonstrate validated MOA are products that will remain on the market and continue to be improved as the science develops.
Explore the science behind PSI Technology on our Our Science page, or browse the full portfolio of published research on our website.
