Plants produce a huge array of natural products (secondary metabolites). These compounds have important ecological functions, providing protection against attack by herbivores and microbes and serving as attractants for pollinators and seed-dispersing agents. They may also contribute to competition and invasiveness by suppressing the growth of neighboring plant species (a phenomenon known as allelopathy). Humans exploit natural products as sources of drugs, flavoring agents, fragrances and for a wide range of other applications. Rapid progress has been made in recent years in understanding...