Biology · Plant Growth and Development · NEET
| Role in growth | ABA: inhibits growth | GA: promotes growth |
| Seed dormancy | ABA: induces dormancy | GA: breaks dormancy |
| Germination | ABA: inhibits germination | GA: promotes germination |
| Stomata | ABA: closes stomata | GA: no such closing role |
ABA is called the stress hormone because it helps a plant survive bad conditions like drought, cold, and injury. During water shortage, ABA closes the stomata so the plant loses less water. It also increases the plant's tolerance to many kinds of stress. So ABA is the hormone that switches the plant into 'survival mode' when the environment is harsh. This exact NCERT line is a favourite for NEET.
ABA closes stomata. When the plant is short of water, ABA stimulates the closure (shutting) of stomata so that water is not lost through them. Students often confuse this and think ABA opens stomata, but that is wrong. Remember: stress hormone = shut the doors = close stomata to save water.
ABA is a growth inhibitor. NCERT says it acts as a general plant growth inhibitor and an inhibitor of plant metabolism. It also inhibits seed germination. So it belongs to the inhibitor group of PGRs, along with dormancy and abscission activities. A NEET 2025 statement question tested exactly this: 'Abscisic acid is a plant growth promoter' is FALSE.
ABA causes seed dormancy, not germination. It induces dormancy, which helps seeds withstand desiccation (drying) and other unfavourable conditions. It also plays a role in seed development and maturation. In contrast, gibberellin (GA) breaks dormancy and promotes germination. So ABA and GA act as antagonists here.
ABA and gibberellins are antagonists, meaning they have opposite effects. GA promotes growth, breaks seed dormancy, and helps germination and stem elongation. ABA inhibits growth, induces seed dormancy, and inhibits germination. In most situations NCERT states ABA acts as an antagonist to GAs. This antagonism is a common NEET matching-question point.
Which of the following is not an inhibitory substance governing seed dormancy?
Read the statements: A. Parthenocarpy can be induced by auxins. B. PGRs can be involved in promotion as well as inhibition of growth. C. Dedifferentiation is a pre-requisite for re-differentiation. D. Abscisic acid is a plant growth promoter. E. Apical dominance promotes the growth of lateral buds. Choose the option with all correct statements.
Match List-I (Growth Regulator) with List-II: A. 2,4-D B. GA3 C. Kinetin D. ABA | I. Brewing industry II. Stimulation of stomatal closure III. Herbicide IV. Nutrient mobilisation
Try the real previous-year questions from this chapter — each with the answer and a full solution.
ABA closes stomata during water stress, induces and maintains seed dormancy, inhibits seed germination, acts as a general growth and metabolism inhibitor, and increases the plant's tolerance to stresses. It also has a role in seed development and maturation.
According to NCERT, abscisic acid is a derivative of carotenoids. Remember the chemical origins: auxin=indole, cytokinin=adenine, ABA=carotenoid, gibberellin=terpene, ethylene=gas.
Three inhibitors discovered separately, named inhibitor-B, abscission II and dormin, were later found to be chemically identical and named abscisic acid (ABA). The name reflects its early discovered roles in abscission and dormancy.
Yes. In most situations ABA acts as an antagonist to gibberellins (GAs). GA promotes growth and germination, while ABA inhibits growth and induces dormancy, so their effects oppose each other.
During water shortage, ABA stimulates stomatal closure so the plant loses less water through the stomata, and it raises the plant's tolerance to stress. This water-saving action is why ABA is called the stress hormone.
