Plants are considered as source of commercially important phytochemicals that include metabolites of primary and secondary metabolism wherein primary metabolites are present throughout the plant kingdom and secondary metabolites have a more limited distribution and specialized function. The secondary metabolites are of major interest because of their different functions and their impressive biological activities ranging from antimicrobial, antibiotic, insecticidal, and hormonal properties to highly important pharmacological and pharmaceutical activities. The plant secondary metabolites, therefore, are widely used in aromatic, therapeutic, or chemical industries. This chapter surveys the reports of recent investigations involving rhizospheric microorganisms especially plant growth-promoting rhizobacteria and arbuscular mycorrhizal fungi that could change the production and accumulation of plant pharmacologically active compounds.
