Plant resins—their formation, secretion and possible functions

TLDR: This chapter focuses on the external resins that are secreted onto leaf surfaces, but it also provides information on resins, which remain within the plant, and other related plant products.

Abstract: Plant resins pose interesting ecological, taxonomic, physiological, and biochemical problems. This chapter briefly describes the resins in chemical terms and presents their contrast with certain other plant products. Resins are nonvolatile products of plants, from which they exude naturally (surface resins) or can be obtained by incision or infection (internal resins). They are insoluble in water but soluble in organic solvents. Stable, inert, and amorphous, they become sticky when heated and are fusible with no sharp melting points. They are mixtures of compounds, including flavonoids, terpenoids, and fatty substances. Resins are usually produced in specialized surface glands (glandular hairs) or internal ducts. Such ducts are widespread in certain families and occur in both woody and nonwoody plants. They are more common in gymnosperms and dicotyledons than in monocotyledons. The chapter focuses on the external resins that are secreted onto leaf surfaces, but it also provides information on resins, which remain within the plant, and other related plant products.