• Grasses accumulate high amounts of silica deposits in tissues of all their organs, especiallyat mature stage. However, when and under which conditions do grass seedlings begin to produce these silica deposits and their relation with anatomy and developmentis little known. Here we investigated the silicification process in the first leavesand roots of seedlings of Bothriochloa laguroides grown in different substrate and Sitreatments. • The distribution and content of silica deposits in the organs of the seedlings grownunder different conditions were analyzed through staining techniques and SEM-EDAXanalyses. • Leaf silica deposits were accumulated 3–4 days after the first leaf emergence, alsounder low silica solution (0.17–0.2 mM). Their location was mainly restricted to shortcostal cells from basal sectors, and scarcely in trichomes and xylem at tips. Silica contentin leaves increased with the age of the seedlings. Roots presented dome-shaped silica aggregates, between 4–12 lm of diameter, located in the inner tangential wall ofendodermal cells and similar to those produced at maturity. • Silicification begins early in the first photosynthetic leaf, and silica distribution isopposite to that found in mature plants, mainly restricted to basal sectors, probablyacting as a reinforcing element. The fast incorporation of solid amorphous silica inleaves and roots, may be useful for farm applications in species that are Si-fertilized