Phosphites play a fundamental role in the physiological activity of plants; they are phosphate fertilisers in which phosphorus is present in the form of ions (PO₃^3-).  The slightly unstable phosphite molecules tend to react and have relatively immediate effects. The great mobility of the phosphite ion, due to its peculiar ascending and descending system, together with its ease of absorption, determine a homogeneous availability of elements on all active sites of the plant with undeniable advantages on the balance of leaf and root activity. The consequent enhancement of the absorption activity from the soil has a positive effect on plant productivity and on the qualitative and organoleptic characteristics of the product.

Phosphites, in addition to their nutritional action, stimulate the plant’s self-defences (Systemic Induced Resistance). They act as elicitors that signal the attack of phytopathogenic microorganisms on the plant by inducing biosynthesis and translocation of phytoalexins.

Phytoalexins are polyaromatic compounds with antimicrobial properties, they increase resistance to attacks of phytopathogens and act directly in the phenomena of breakdown of the cell membranes of pathogenic bacteria, causing their destruction.