Plant exudation is the process by which plants release substances from their roots, stems, and leaves. Two common examples of plant exudation are RESIN and GUM. RESIN is a sticky, yellowish-brown substance that is secreted by certain trees and plants. It is often used in varnishes, lacquers, and other products. GUM is a thick, sticky substance that is secreted by certain plants. It is often used as an adhesive or to make chewing GUM.