Although the plants are immobile, they have a series of characteristics which allows them to interact with the environment, such as autotrophy (they are able to manufacture their own food through photosynthesis), the presence of a cell wall and lignin that confers them rigidity to be able to expand in the third dimension and in this way reach sources of nutrients (light, CO2, water and mineral salts). As in all interactions, it is essential to transmit information from one part of the body to another, as well as between different individuals. The transmission of information in plants is carried out by chemical substances called plant hormones.

As mentioned before, there are microorganisms capable of synthesizing auxins. In many cases they are microorganisms strongly linked to the plant kingdom, such as the bacteria found in the rhizosphere (Pseudomonas, Azospirillum, etc) and are the product of the coevolution of plants with microorganisms.

To carry out their action, auxins are recognized in the plant by a series of receptors. In order to be recognized, they must meet a series of structural requirements. The AIA molecule was studied as a model and it was stipulated that the distribution and distance between the positive and negative charge is important in the determination of the auxinic function, making the presence of the indole ring not an essential condition, as was thought at first. Thus, there are molecules with auxin functionality lacking the indole ring.

Auxins intervene in cell growth, controlling cell division and thus influencing the formation of secondary roots. For this reason, they are widely used in agriculture for the rooting of cuttings. They also intervene in the apical dominance, stem elongation, vascular differentiation (mainly in the cambium), leaf ordering in the stem (phyllotaxis) or in abscission processes of leaves and fruits.