Plants use complex metabolic pathways to fend off pathogens, to coordinate reproduction with changes in day length, to accommodate environmental changes, and to select developmental pathways most suited to a given place and time. ~ American biologist Pamela Hines & American botanist Laura Zahn
Plants are unsurpassed chemists. DNA, sugars, starches, proteins, and oils are all constructed on carbon backbones, bonded to form complex compounds. Unlike animals, which produce these substances autonomically, plants are consciously involved.
Metabolites are the products of plant metabolism. Metabolites are classified by perceived essentiality: primary and secondary.
Primary metabolites are the necessary chemical products for energy, construction, and reproduction. Without the requisite materials to produce primary metabolites, a plant quickly dies.
Secondary metabolites are specialty compounds, commonly concocted to defend against herbivory, from creatures large and small. Certain secondary metabolites are somewhat more constructive: carving exclusive territories under competitive conditions, by inhibiting germination and growth of other species, and creating conducive conditions for favored allies, notably microbes and pollinators.
Unlike primary metabolites, secondary metabolites are not essential to a plant’s immediate health.
Plants do not produce all their metabolites in every cell. Tissue-specific factories synthesize many metabolites, especially secondary metabolites, as these are typically hazardous materials.