The chemical role of plant roots in the mechanisms of stone deterioration is discussed. A review of experimental studies shows that this chemical action is exercised by the acidity of the rootlets and by excretion of inorganic and organic compounds, with aggressive or chelating capabilities. The mineral etching is due to contact-exchange mechanisms of ions in solution. Modifications in the mineral composition of stone are often induced. A deposit of some mineral elements in vegetative structures is also observed, confirming the chemical action. Preliminary findings on the acidity of roots of some ruderal species are given. A more detailed study of chemical and mechanical actions of specific ruderal plants present on stone monuments is necessary. -- AATA