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IAA vs IBA: What's the Difference Between Indole-3-Acetic Acid and Indole-3-Butyric Acid?
Jul 08,2026
Indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) are both auxin-type plant growth regulators. Although they have similar physiological functions, they differ significantly in stability, transport characteristics, and practical applications. Understanding these differences helps growers select the most suitable auxin for rooting, seed germination, transplanting, and crop production.
I. Indole-3-Acetic Acid (IAA)
What is IAA?
Indole-3-acetic acid (IAA) is a plant growth promoter that exerts a wide range of physiological effects. It maintains apical dominance, induces the translocation of assimilates toward harvestable products, promotes fruit setting, rooting of plant cuttings, seed germination, fruit ripening, formation of parthenocarpic (seedless) fruits, graft union healing, cell elongation, and differentiation of female flowers.
Once absorbed by plants, IAA is transported exclusively in a polar manner, moving unidirectionally from the shoot apex toward the base.
Auxins exhibit concentration-dependent effects. Low concentrations stimulate growth, whereas high concentrations inhibit growth. Therefore, the physiological response to IAA depends on the endogenous auxin level within the plant.
Applications of IAA
IAA is commonly used to:
- Improve seed germination in rice, peanuts, cotton, and tung trees.
- Promote rooting of cuttings from plum, apple, pine, grapevine, mulberry, poplar, dawn redwood, spirea, potato, sweet potato, and kiwifruit.
- Stimulate vegetative growth in potato, maize, highland barley, broad bean, sugar beet, radish, and other legumes to improve yield.
Stability of IAA
IAA is readily degraded within plants, reducing its effectiveness.
To reduce degradation, polyphenolic compounds such as:
- Catechol
- Pyrocatechol
- Caffeic acid
- Quercetin
May be added to IAA solutions because they inhibit indole-3-acetic acid oxidase, the enzyme responsible for IAA degradation.
II. Indole-3-Butyric Acid (IBA)
What is IBA?
Indole-3-butyric acid (IBA) is stable under acidic conditions but forms salts under alkaline conditions. It gradually decomposes under light and degrades rapidly in soil.
Its physiological activity is similar to IAA, but after absorption, it is not readily transported within plants and generally remains at the application site.
Because of this characteristic, IBA is mainly used for promoting root formation.
Rooting Effects of IBA
IBA induces root primordia formation, stimulates cell division, promotes new root growth, and facilitates vascular differentiation.
Compared with IAA, IBA is more effective at promoting adventitious root formation.
IBA produces:
- Fine roots
- Dense roots
- Highly branched root systems
In contrast, NAA generally produces:
- Thick roots
- Fleshy roots
- Multi-branched root systems
Therefore, combining IBA with NAA often yields superior rooting results. For commercial propagation, a pre-formulated IBA + NAA rooting product can provide convenient application and consistent performance. Learn more about our IBA + NAA 2% SP rooting formulation.
Applications of IBA
IBA is commonly used for:
- Root dipping during transplanting of woody and herbaceous plants
- Rooting of hardwood cuttings
- Seed soaking
- Seed dressing
Recommended concentrations are:
| Application | Recommended concentration |
|---|---|
| Herbaceous plant transplanting | 10–20 mg/kg |
| Woody plant transplanting | 50 mg/kg |
| Cutting treatment | 50–100 mg/kg |
| Woody seed soaking | 100 mg/kg |
| Herbaceous seed soaking | 10–20 mg/kg |
Precautions for IBA
When using IBA:
- Avoid contact with leaves and terminal buds during cutting treatment.
- Apply concentrations according to crop requirements.
- A 0.06% IBA solution may cause phytotoxicity in fig plants.
- Since IBA is insoluble in water, dissolve it in ethanol before diluting with water.
Stability of IBA
Compared with IAA, IBA is less susceptible to degradation by indole-3-acetic acid oxidase.
Unlike NAA, which may damage shoots when applied at excessive concentrations, IBA is not readily transported after absorption and remains localized at the application site, making it relatively safer to use.
III. IAA vs IBA: Key Differences
| Feature | IAA | IBA |
|---|---|---|
| Stability in plants | Easily degraded | More stable |
| Transport | Polar transport throughout the plant | Mainly remains at application site |
| Main application | General plant growth regulation | Root induction |
| Rooting ability | Good | Stronger than IAA |
| Enzymatic degradation | Easily degraded by IAA oxidase | More resistant |
| Root characteristics | — | Produces fine, dense, highly branched roots |
| Solubility | — | Insoluble in water; dissolve in ethanol first |
| Safety | Depends on endogenous auxin level | Generally safer because of limited translocation |
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