Essential Oils and Resins

Abstract

Essential oils/volatile oils are odoriferous complex mixtures of hydrocarbons and their oxygenated derivatives produced by specialized cells present in different parts of plants. In general, essential oil constituents are terpenes (monoterpenes and sesquiterpenes), phenylpropenes and in some plants dominated by allylpolysulfides or allylisothiocyanates. The essential oils play important roles against abiotic factors and biotic factors. They also attract animals for pollination and seed dispersal. Herbivore induced plant volatiles communicate between infested plants and natural insect enemies and warn neighbouring plants against forthcoming attacks. 1,8-Cineole and camphor have an allelopathic effect and inhibit germination and growth of seedlings of annual herbs. Essential oils are also used in the cosmetics industries, aromatherapy, and as flavouring agents in food and medicines. Resins are chemically complex amorphous products of plant tissues. Resins have deterrent effects to herbivores or inhibitory effects to pathogens. The terpenes and phenolic compounds may attract beneficiary parasitoids or predators of herbivores attacking the plants. Many resinous products are also used in medicine, toothpastes, mouthwash etc.