Understanding biostimulation

Biostimulation

In its etymological sense, a biostimulant is a product that “stimulates living organisms”.

Biostimulants represent a new category of products that has been developed for several decades. Based on its expertise in  its plant research programmes since the 1990s, Frayssinet was one of the first companies to market a biostimulant.

Today, among the great variety of claims put forward (growth stimulators, soil activators, biofertilisers or phytostimulants…) and the origins (plant extracts, biomolecules, silica, humic acids…), the range of solutions is varied.

The mechanism by which plants adapt to stress

Understanding plant biostimulation means first and foremost understanding how a plant functions and how it perceives and interacts with its environment.

The function of biostimulants is to support the physiological processes of plants by acting on well-known metabolic pathways during their growing cycle, protecting them from the impact of abiotic stresses.

The 3 key stages in the plant’s reaction “when faced with danger” are :

> Perception: recognition by specific membrane receptors of the “non-self” (DAMP/MAMP1), which leads to the identification of the stress, of the “abnormal” condition or danger.
> Signal transduction: i.e. the dissemination of the information within the plant. This takes place from cell to cell via a flow of calcium.
> The cellular response through the expression of resistance genes, signals and regulation of hormonal status, enabling induced local resistance. Basic resistance metabolic processes and/or an adaptive responses are then activated via an integrative system (reactive oxygen species (ROS) / phytohormones).

Activation of the cellular response is counterbalanced by enzymatic detoxification systems or antioxidant compounds. In the event of excessive stress or danger, the defence systems can go as far as the destruction of the cell.

1 Damage Associated Molecular Patterns/Microbe-associated Molecula Patterns

Biostimulants help to maximise genetic potential and maintain activity during periods of stress, thereby securing yields. If climatic conditions are favourable, biostimulants will have a minor effect. Since periods of stress are unpredictable, biostimulants should be seen as insurance against climatic ups and downs.

Soil biostimulation

In the definition of biostimulants in the latest EU regulation, the notion of “availability of nutrients confined in the soil or rhizosphere” appears. Some products can be classified as biostimulants by acting indirectly on one of the components of the soil to release or help fetch nutrients. In this way, by optimising the resource available, this type of biostimulant also improves plant function. Soil biostimulants only work if the soil contains organic matter and nutrients.

Two main modes of action are expected: activation of telluric or rhizospheric flora and release and provision of nutrients.

Getting to market

Definition

The European Commission defines biostimulants as a product that stimulates the plant nutrition process independently of the nutrients it contains, with the sole aim of improving one or more of the following characteristics of plants or their rhizosphere:

> the efficiency with which nutritional elements (N, P, K, Mg, Ca, etc.) are used;
> the availability of nutrients confined in the soil or rhizosphere;
> resistance to abiotic stresses (low temperatures, water stress, salinity, etc.);
> crop and harvest quality.

Biostimulants can be natural substances (biomolecules, plant and algae extracts, micro-organisms), mineral substances or even synthetic, non-nutritive molecules acting to improve the physiological metabolism of crops, by application to plants or the soil.

More than their constituents or their nature, it is their mechanisms of action and their claims that will define them.

Regulatory context for biostimulants

In France, biostimulants are part of the MFSC (Matières Fertilisantes et Supports de Culture) family. Biostimulants do not have the same application standards as soil improvers, fertilisers or growing media. In order to be placed on the market, all biostimulant products be approved beforehand and obtain a Marketing Authorisation (MA).

The E-phy website, managed by ANSES, can be used to check whether a biostimulant has a marketing authorisation, its claims and its uses.

There are three ways of obtaining a marketing authorisation in France:

> a national approval process under the supervision of ANSES, which checks the efficacy of the solution (significant trials on each authorised use), the mode of action and a toxicological assessment.
> a national mutual recognition process in compliance with European rules. The applicant must demonstrate to the national authorities that the product is marketed as a biostimulant in another EU country. The assessment is purely documentary, with no verification of efficacy or toxicity.
> A European assessment and registration process under regulation 2019/1009 with an efficacy dossier and proof of absence of contaminants (TMEs, contaminants, pathogens).

Once approval has been obtained, and provided the marketing authorisation expressly states “authorised as an agronomic additive”, biostimulants may be marketed mixed with crop supports or fertilising materials in accordance with authorised French standards (NF U 44-551/A4 and NF U44-204).

Biostimulants and organic fertilisation: the winning synergy