The Indole acetic acid in bacteria, fungi and plants

OPEN ACCESS Indole acetic acid (AIA) is the most important plant growth hormone since it intervenes in the mechanisms of cell growth and differentiation and is produced mostly in the meristematic zones of the plant for apical dominance or root growth. AIA is also produced in root nodules and plant galls. In the latter cases, its presence is associated with endophytic bacteria. Although it is a plant growth hormone, it is also produced by bacteria such as Azospirillum brasilense and Bradyrhizobium japonicum. These species live in the soil (rhizosphere) or can colonize the roots (endophytic) of their hosts. From these bacteria, there are also isolates that are nitrogen ixers, which in addition to providing growth factors to plants, contribute by releasing nitrogenous molecules that improve plant nutrition.