This procedure quantifies endomycorrhizal spores and vesicles within the biostimulant by means of microscopy, after sieving, extraction, and staining of its organic components.

The methodology used follows the 2022 UNE-CEN/TS 17722 and 17725 technical specifications for the analysis of plant biostimulants. These standards are applied alongside the corresponding protocols for biostimulant sampling and sample preparation.

The analysis requires five replicates per biostimulant sample, both for root staining and counting, as well as for assessing viable vesicles.