Abstract: Auxin plays an important role in regulating the growth and heavy metal resistance of plants. The healthy growth of plants is a result of the homeostasis of auxin and the balanced plant metabolism under heavy metal stress. The homeostasis of auxin is strictly regulated by its biosynthesis, conjugation, hydrolysis and catabolism. Some enzymes and genes involved in auxin biosynthesis and degradation have been identified or cloned. However, little information is available regarding the enzymes and genes concerning auxin biosynthesis and degradation under heavy metal stress. Understanding the mechanisms related to auxin biosynthesis and degradation under heavy metal stress will be helpful to properly regulate plant growth during phytoremediation. Taking indoleacetic acid (IAA, a main representative substance of auxin) as an example, this review focused on the recent advances in the mechanisms of IAA biosynthesis and degradation, and its existing forms in plants under heavy metal stress. Prospects in this field have been proposed from the viewpoints of the relative importance of IAA biosynthesis routes, the variation of IAA forms and their functions, and the interactions among different plant hormones.

Key words: Microcystis aeruginosa, terrestrial plant, allelopathy, algistat