Britannica
Sources used in this answer
How is indole-3-acetic acid involved in plant growth?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
heterocyclic compound
There are many different sulfur-containing heterocycles. One of the best known is thiophene, C4H4S, derivatives of which occur as plant pigments and as other natural products such as biotin.
Indole-3-acetic acid (IAA), also known as -indolylacetic acid, is the most significant naturally occurring auxin, a class of hormones that regulate plant growth. It is synthesized within the plant from the amino acid tryptophan or through the breakdown of glycosides.12
IAA influences plant development through several key mechanisms:
- Cell Elongation: It stimulates growth by acting on the chemical bonds of cell wall carbohydrates, allowing cells to expand irreversibly as they take in water and synthesize new wall material.1
- Tropisms: IAA facilitates directional growth. In phototropism, it accumulates on the shaded side of a stem, causing that side to elongate more and curve the plant toward the light. Similarly, in geotropism, its accumulation on the lower side of a stem generates upward curvature.1
- Developmental Regulation: Beyond elongation, IAA plays a role in cell division, fruit development, root formation, and the inhibition of lateral branching, known as apical dominance.1