# Abscisic acid

> A plant hormone (ABA) that signals water stress, closes stomata and maintains seed dormancy.

- Canonical: https://genetixbay.com/knowledge/glossary/abscisic-acid.html
- Also written: ABA, abscisin, dormin, stress hormone
- Glossary category: Plant biology · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Abscisic acid (ABA) is the plant's main drought and stress hormone. When roots dry out or leaves lose water, ABA levels rise within minutes and [guard cells](https://genetixbay.com/knowledge/glossary/stomata.md) close stomata to cut water loss. ABA also keeps seeds dormant, slows growth under stress and helps leaves cope with cold and salinity. Despite the name, its role in abscission (leaf drop) is minor; [ethylene](https://genetixbay.com/knowledge/glossary/ethylene.md) does most of that.

## In practice

ABA is why plants stop drinking and growing when the medium gets [too dry](https://genetixbay.com/knowledge/glossary/over-drying.md) or the air too harsh. With stomata shut, CO₂ uptake falls and growth stalls, even with perfect light.

It's also part of the story behind controlled late drought. Caplan et al. (2019) reported that a moderate drought stress in late flower raised [cannabinoid](https://genetixbay.com/knowledge/glossary/cannabinoid.md) concentration and yield per area in their trial. GenetixBay endorses mild late [dry-backs](https://genetixbay.com/knowledge/glossary/dryback.md) where a cultivar tolerates it (Supported, house-endorsed), and notes every cultivar responds differently. Push too hard and you lose yield.

## Don't confuse with

- **Ethylene**: the ripening and [senescence](https://genetixbay.com/knowledge/glossary/senescence.md) gas.
- **Cytokinin**: a growth hormone that ABA broadly opposes.
- **Wilting**: the visible result of water loss, which ABA tries to prevent.

## Related terms

[Stomata](https://genetixbay.com/knowledge/glossary/stomata.md), [Transpiration](https://genetixbay.com/knowledge/glossary/transpiration.md), [Ethylene](https://genetixbay.com/knowledge/glossary/ethylene.md), [Senescence](https://genetixbay.com/knowledge/glossary/senescence.md)

## Read more

- [VPD explained: vapour pressure deficit for cannabis growers](https://genetixbay.com/knowledge/environment/vpd-explained.md)
- [Drooping cannabis: overwatering vs underwatering](https://genetixbay.com/knowledge/diagnosis/drooping-overwatering-vs-underwatering.md)

## Sources

1. Taiz L, Zeiger E, Møller IM, Murphy A. 2015. Plant Physiology and Development, 6th edition. Sinauer Associates.
2. Caplan D, Dixon M, Zheng Y. 2019. Increasing inflorescence dry weight and cannabinoid content in medical cannabis using controlled drought stress. HortScience 54(5):964-969. https://doi.org/10.21273/HORTSCI13510-18