Enhanced Efficiency of Medicinal and Aromatic Plants by PGPRs

Plant growth-promoting rhizobacteria (PGPRs) are a specific group of soil microorganisms that aggressively colonize the rhizosphere and rhizoplane, and substantially improve plant growth and efficiency via direct or indirect mechanisms. Moreover, infection by microorganisms as well as physiological and genetic factors and environmental conditions are the main agents affecting the accumulation and composition of secondary metabolites. As an environmentally friendly strategy, PGPRs should be considered to achieve sustainable high yields of industrially important secondary metabolites in plants using minimum chemical inputs. This chapter aims to introduce proven or putative mechanisms by which PGPRs promote seed germination, growth, nutrient acquisition, and production of primary and secondary metabolites in aromatic and medicinal plants.