Gibberellins In Plants- Structure, Functions and Applications

In the human body, different types of hormones help perform various metabolic activities. The hormones are chemical messengers produced by the specific glands in our body. Similarly, there are several hormones that help in the development of plants. Gibberellins are plant hormones that help stimulate several functions of plants, such as growth, flowering and germination.

Table of Contents:

What are Gibberellins In Plants?
Structure of Gibberellin
Function of Gibberellins
Applications of Gibberellins
Practice Problems
Frequently Asked Questions

What are Gibberellins In Plants?

Plants have plant hormones that are called plant growth regulators or promoters. Gibberellins are one of the plant hormones that help in developmental processes such as stimulating the growth of the stem, flowering, enzyme induction, germination, etc.

Gibberellin plays an important role in the elongation of the stem. The stem initiates its growth only when it is applied in low concentration to a bush. The internodes of the plants grow dramatically, and they become so long to climb. Gibberellins can overcome the genetic limitation of dwarf varieties of plants. There are over 70+ gibberellins isolated, such as GA1, GA2, GA3, etc. Out of them, GA3 Gibberellic acid is the most important plant growth regulator that is widely studied.

Structure of Gibberellin

Gibberellin is a form of diterpenoid. It is considered the basis of molecules like vitamins A and E. However, the structure of all gibberellins is the same, with the attachment of several side groups. Thus, these groups determine the several functions of gibberellins which are unique in different tissues.

Chemical formula	C₁₉H₂₂O₆
Molar mass	346.37 g/mol
Solubility in water	5 g/l (20 °C)
Melting point	233 to 235 °C

Function of Gibberellins

Some of the important functions of gibberellins are given below:

Seed Germination:

Seeds such as tobacco and lettuce are very light-sensitive, and in the absence of sunlight, they exhibit poor germination. If the seeds are exposed to sunlight, the germination process of seeds begins rapidly. By treating the seeds with gibberellic acid, the requirement of light can be prevented.

Dormancy of Buds

During autumn, the buds formed at this time stay dormant until next spring. By treating the buds with gibberellin, the dormancy can be overcome.

Growth of Roots

Gibberellins don't play any significant role in the growth of the roots. However, growth inhibition can take place in a few plants with higher concentrations.

Internode Elongation

The elongation of internodes is the most profound effect of gibberellins on the growth of plants. The genetic dwarfism of plants such as peas and maize can be overcome by gibberellins. The internodes of pea plants are short with expanded leaves. By treating the plants with gibberellin, the internodes can be expanded, resulting in tall plants. Gibberellins show their impact by altering gene transcription.

Applications of Gibberellins

Gibberellins are used to boost the growth of plants. They are obtained from fungi for commercial purposes.

It is used to facilitate the process of germination of seeds and elongation of genetically dwarf plants.
Gibberellin is sprayed on grapevines to enlarge them.
It helps in breaking the dormancy.
Gibberellin is sprayed on biennial plants that grow only in low temperatures. This helps the plants to flower irrespective of temperature.
It is also sprayed on sugarcane plants to increase the length of the stem.
It helps in parthenocarpy.

Practice Problems

Q1. Which of the following is the incorrect function of Gibberellins?

a. Germination of seed
b. Elongation of stem
c. Reproduction in plants
d. Flowering in plants

Answer: c. Reproduction in plants

Q2. Which of the following is the chemical formula of Gibberellins?

a. C₁₉H₂₂O₆
b. C₁₇H₂₁O₆
c. C₁₉H₂₀O₉
d. C₁₉H₂₂O₉

Answer: a. C₁₉H₂₂O₆

Q3. Which of the following shows poor germination in the absence of light?

a. Mango
b. Beans
c. Tobacco
d. None of the above

Answer: c. Tobacco

Explanation: Seeds such as tobacco and lettuce are very light sensitive and in the absence of sunlight, they exhibit poor germination. If the seeds are exposed to sunlight, the germination process of seeds begins rapidly.

Frequently Asked Questions

Q1. Where are gibberellins formed?
Answer: Gibberellins are produced by the terpenoid pathway in the plastids. Later, it is transformed in the endoplasmic reticulum and cytoplasm to reach their biologically active stage.

Q2. Who discovered gibberellic acid?
Answer: Kurosawa, a Japanese Botanist, discovered gibberellic acid while determining the rice foolish seedling disease.

Q3.How are cells elongated by gibberellins?
Answer: The rheological properties of the cell wall are altered, which results in a lowering of the water potential of the cell. This allows the release of water and increases the volume of the cell.