Secondary plant constituents

Secondary plant constituents (or substances or chemicals) are plant products which are not of obvious nutritional value to plant development or herbivore nutrition, and are often specific to distinct plant groups. They are usually produced in small quantities and confer special attributes to the plants that produce them (e.g. color, taste). They may serve as feeding deterrents, repellents or conversely attractants, or as pheromones and kairomones.