Gums and resins Gums form when the cellulose in plant cell walls breaks down. Originally used as adhesives, today they have many other uses. For example, gum Arabic harvested from Acacia trees is used as an adhesive on postage stamps, and to thicken medicines and inks. Certain plants secrete resins from specialised cells. Aromatic and flammable, they have long been used in medicines, embalming, incense and torches.