Tree exudation is the process by which trees release substances from their roots, bark, or leaves. The substances released are known as exudates and can include resins, rosins, SAP, and GUM. RESIN is a sticky, yellowish-brown substance that is secreted by some trees and plants. ROSIN is a solid form of RESIN that is used in varnishes and adhesives. SAP is a sweet, sticky liquid that is produced by trees and other plants. GUM is a thick, sticky substance that is secreted by certain trees and plants.