Which of these is not a function of auxin?

The correct option is inducing dormancy.

Auxins are a class of plant hormones (or phytohormones) that play an essential role in coordinating many growth and behavioral processes in plant life cycles. Let us analyze each option to understand why inducing dormancy is not a function of auxin:

1. Inducing callus formation: In plant tissue culture, auxin, typically in combination with cytokinin, is used to stimulate cell division and induce the formation of a callus (an unorganized mass of cells). Therefore, this is a function of auxin.
2. Enhancing cell division: Auxins promote cell elongation and, particularly in the presence of cytokinins, stimulate cell division in the cambium and other meristematic tissues. Thus, this is a function of auxin.
3. Maintaining apical dominance: Apical dominance is the phenomenon where the main central stem of the plant grows more vigorously than the lateral stems. Auxin is produced in the apical bud and flows downwards, suppressing the growth of lateral buds. Hence, maintaining apical dominance is a classic function of auxin.
4. Inducing dormancy: Dormancy, especially in seeds and buds, is primarily regulated and induced by another plant hormone called Abscisic Acid (ABA). Auxins, on the contrary, are generally associated with promoting growth, breaking dormancy in certain contexts (like initiating rooting), or preventing premature abscission. Therefore, inducing dormancy is not a function of auxin.

Consequently, inducing dormancy is the correct answer as it is regulated by abscisic acid rather than auxin.