It is not considered an essential element in the plants, but its beneficial effect on them is recognized.

Si is the second most abundant element on the earth’s crust, being in its vast majority in the form of polysilicic acid, not assimilable by the plant. Silicon is taken up by the roots in their soluble form as silicic acid Si(OH)4, accumulating in plants in the form of silica SiO2.

Silification varies between organs, phenological and spatial stages, according to their abundance in the soil. In recent years, the interest on silica has gained great relevance since it has been found:

• Its protective function against insects and pathogenic fungi,
• Its contribution in the morpho-structure of different plant tissues,
• Its stimulus in mechanisms of resistance against diseases and detoxification of metals,
• And an increase in tolerance to biotic and abiotic stresses (tolerance to drought, delay in the defoliation of some crops due to lack of irrigation).

The efficacy of the hydrophobic oxide (SiO2, nH2O) in the cell wall near the cuticle of the leaf surface is demonstrated, increasing the impermeability and resistance to the entry of a fungal attack.

These processes, related to mineral nutrition, constitute the main structural resistance of plants against pests and diseases in grasses and in the endodermis of the root.