As sessile organisms, plants have evolved an amazing array of metabolic pathways leading
to molecules capable of responding promptly and effectively to stress situations imposed
by biotic and abiotic factors. These pathways, often recruited during biological evolution
from essential primary metabolism pathways upon initial gene duplication, combine
carbon, hydrogen, oxygen, nitrogen, and sulfur into molecules that are capable of herbivore
deterrence, tri-trophic signaling (i.e., attracting herbivore predators and parasites),
pathogen inhibition, integrating defense responses, UV absorption, quenching of reactive
oxygen species, allelopathic activity, attracting pollinators, or seed dispersing animals,
heat dissipation, among other activities. Throughout the kingdom Plantae, there are tens
of thousands of molecules, frequently restricted to specific taxonomic groups, which play
this major role of plant interaction with the environment and are extremely important
for plant fitness; these are historically referred to as secondary metabolites, also known as
natural products.