secondary metabolites pathway

In natural habitats, plants are surrounded by an enormous number of potential enemies. Nearly all ecosystems contain a wide variety of bacteria, viruses, fungi, nematodes, mites, insects, mammals, and other herbivorous animals. By their nature, plants cannot avoid these herbivores and pathogens simply by moving away; they must protect themselves in other ways. Their first line of defense involves the plant surface. The cuticle (a waxy outer layer) and the periderm (secondary protectiv tissue).
A diverse group of plant compounds, commonly referred to as sec¬ondary metabolites, also defends plants against a variety of herbi¬vores and pathogenic microbes. Some secondary metabolites serve other important functions as well, such as providing structural sup¬port, as in the case of lignin, or acting as pigments, as in the case of the anthocyanins. They serve as attractants (odor, color, taste) for pollinators and seed-dispersing animals. Study of these substances was pioneered by organic chemists of the nineteenth and early twentieth centuries who were interested in them because of their importance as medicinal drugs, poisons, flavors, and industrial materials.