Abscisic Acid (ABA): Overview, Discovery, Types, Bioassay, Functions

Contents Show Table of Contents

Abscisic Acid is well known for Abscision of leaves. Abscisic Acid is mildly acidic growth hormone. function as a General growth inhibitor bye counteracting other hormones. As we know that auxins gibberellins cytokinins are a growth-promoting hormone. Abscisic Acid is just the opposite of these hormones.

IUPAC name of Abscisic Acid (ABA)

International Union of Pure and Applied Chemistry (IUPAC) name of Abscisic Acid (ABA) is (2Z,4E)-5-[(1S)-1-hydroxy-2,6,6-trimethyl-4-oxocyclohex-2-en-1-yl]-3-methylpenta-2,4-dienoic acid.

Other Names of Abscisic Acid (ABA)

These are some other Names used for

(2Z,4E)-(S)-5-(1-Hydroxy-2, 6,6-trimethyl-4-oxo-2-cyclohexen-1-yl)-3-methyl-2,4-pentanedienoic acid
Dormic acid
Dormin

Properties

The chemical formula of Abscisic Acid (ABA) is C₁₅H₂₀O₄ . has 264.321 g·mol⁻¹ Molar mass and 1.193 g/mL density. The melting point of is 163 °C (325 °F; 436 K). has 4.868 pKa Acidity and 9.129 pK_b Basicity.

Discovery

Addicott et al first isolated Abscisic Acid in 1963 from cotton balls. They used term Abscisin II for that isolated substance. Simultaneously Wareing and Cornforth also isolated a substance that can induce bud dormancy. They used term Dormin. Later both these substances we are same and were named abscisic Acid.

Abscisic Acid produced more abundantly inside the chloroplasts of green cells. Abscisic Acid formation stimulated by drought, waterlogging and other adverse environmental conditions. Therefore it is popular as a stress hormone.

formed from Malonic acid xanthophyll. dextrorotatory cis sesquiterpene. Abscisic Acid is transported to all parts of the plants through the diffusion process as well as through conductive channels.

Bioassay of Abscisic Acid

Testing of biological activity of a substance by employing living material is known as Bio essay. With the help of bioassay, we can test the effect of any substance on any living thing.

Seedling growth inhibition test- Mohanty, Anjaneyulu, and Shridhar performed a test in 1979 to check the the the growth inhibition effect of abscisic acid on rice plants. They measured the length of second leaf teeth after 6 days of growth and noticed the inhibition.
Inhibition of Alpha-amylase synthesis in Barley endosperm test-
abscisic acid inhibits the synthesis of Alpha-amylase in the aleurone layers. These are that aleurone layer which is triggered by gibberellins. Goldschmidt and Monselise developed the bioassay method in 1968. They developed the bio as a method to estimate abscisic acid activity by determining the extent of inhibition of Alpha-amylase synthesis induced by treating Barley seed endosperm with gibberellins.

Biosynthesis of abscisic acid

Zeaxanthin is the first committed ABA precursor for Biosynthesis of abscisic acid. Abscisic acid (ABA) is synthesized in the plastidal2-C-methyl-D-erythritol-4-phosphate (MEP) pathway.
Abscisic acid released during desiccation of the vegetative tissues of plants and when roots encounter soil compaction.
Abscisic acid released at the beginning of the winter period in green fruits. Abscisic acid can be rapidly translocated from the roots to the leaves.
Abscisic acid Produced in response to environmental stress, these adverse conditions may be overheating, water stress, salt stress etc, that’s why Abscisic acid is also known as the stress hormone.

Functions of Abscisic Acid

Growth control- abscisic acid counteract the effect of growth-promoting hormones. Growth promoting hormones are auxins gibberellins and cytokinins.abscisic acid reduces the effect of hormones during the plant growth.
As we already know that growth is primarily controlled by gibberellins. abscisic acid reduces the effect of gibberellins so that abscisic acid known as an anti gibberellic hormone.
Dormancy- abscisic acid induces dormancy of a bus towards the approach of winter because of abscisic acid act as a growth inhibitor. Dormancy of seeds is mainly caused by abscisic acid. abscisic acid induces dormancy so it is also known as dormin. when abscisic acid is overcome by gibberellin birds and seeds sprout out.
Abscission- abscisic acid promotes the association of leaves flowers and fruits in plants. Because of this nature, this hormone is called abscisic acid.
Senescence- abscisic acid causes destruction of chlorophyll in leaves. This stimulates Senescence in leaves. Destruction of chlorophyll affects the growth of the plant. abscisic acid also inhibits the synthesis of protein and RNA. This effect of abscisic acid can be reversed by using cytokinin in lemna.
Antitranspirant- abscisic acid can be used as anti transpirant by using in minute quantity. Leaves reduce transpiration rate true partial closure of stomata.
Hardiness- abscisic acid inhibits the growth of pathogens by promoting cold hardiness.
Flowering- abscisic acid flowering in long-day plants whereas in some short day plants abscisic acid promotes flowering.
Rooting- abscisic acid can be used to promote routes in stem cuttings.

FAQs related to Abscisic Acid

What are the functions of abscisic acid in plants?

1. Promotes abscisic acid is to promote abscission in leaves and fruits.
2. Abscisic acid Act as Antitranspirant by Inducing stomatal closure
3. Decreases the rate of transpiration to prevent water loss
4. Inhibits fruit ripening in plants
5. Induces seed dormancy and inhibits seed germination in plants
6. Delays cell division during growth and inhibits cell growth
8. synthesis of Kinetin nucleotide get inhibited by abscisic acid

What is the chemical formula of abscisic acid?

The chemical formula of abscisic acid is C₁₅H₂₀O₄

Which is the Melting point of abscisic acid?

The Melting point of abscisic acid is 163 °C (325 °F; 436 K)

What is the main function of abscisic acid in plants?

The main function of abscisic acid is to promote abscission in leaves and fruits.

Why is abscisic acid known as a stress hormone in plants?

Abscisic acid is also known as the plant stress hormone because it is synthesized during adverse conditions when the environment is not in favour of plants such as cold, salt, water deficiency, excessive water, high temperature etc. Abscisic acid saves plant life by promoting abscission of fruits and leaves, dormancy of buds etc. Abscisic acid is capable to reverse the actions of other growth-promoting hormones such as auxins, gibberellins, cytokinins etc. Hence Abscisic acid plays a very important role in conditions of stress thats why Abscisic acid is called Stress hormone.

How does abscisic acid inhibit growth?

By delaying cell division and reducing the effect of growth-promoting hormones such as auxins, gibberellins, cytokinins abscisic acid inhibits growth.

Why abscisic acid is known as dormin?

Abscisic acid induces seed dormancy, Bud Dormancy and inhibits seed germination in plants so that abscisic acid is known as Dormin. Wareing and Cornforth used the term “Dormin”

Why is abscisic acid important?

Abscisic acid synthesized during adverse conditions to save plant life from environment adverse conditions such as cold, salt, water deficiency, excessive water, high temperature etc. In adverse conditions, it induces Leaf fall, fruits fall, seed dormancy, Bud Dormancy and inhibits seed germination.

Here we have discussed “Abscisic Acid (ABA): Overview, Discovery, Types, Bioassay, Functions” we hope you like this article. if you have any query or suggestion, please leave a comment on the email. or contact us from contact us page.

Follow our official groups on Telegram, Whatsapp and Facebook