Gibberellins: Definition, Structure, Function, Applications, Uses

What Are Gibberellins?

Gibberellins are members of the phytohormone group, which enables various plant growth and development processes. They are the hormones regulating the critical physiological activities of plants, including seed germination, stem elongation, flowering, and fruit development.

Chemical Properties Of Gibberellins

The chemical properties of Gibberellins are defined below:

Molecular Structure

The molecular structure of Gibberellins is very complex because it mediates a wide variety of biological effects. Hence it is imperative to be familiar with the structure to understand how it interacts with the plant cell to produce such an effect on growth.

Structure And Explanation Of Functional Groups

• Nature: Diterpenoid acid skeleton

• Core structure: Complex structure of four fused rings (gibbane skeleton)

• Functional Groups: Hydroxyl (-OH), ketones in the form of C=O, and carboxyl (-COOH) groups, which are very vital for their activity.

Physical Properties

The physical properties are remarkable concerning its application and stability in various environments.

State And Solubility

• State: Occur as solid crystals or powders.

• Solubility: Soluble in organic solvents such as ethanol and methanol but have poor solubility in water.

Stability And Degradation

• Stability: Light and temperature-sensitive, thus they lose their stability and action depending upon the conditions they are exposed to.

• Degradation: Degrade either with time or in an extreme condition thus reducing their biological function.

Regulation of Gibberellin Production

In such a process, both intrinsic and extrinsic factors act and are followed to achieve control over plant growth effectively. The regulation mechanism is given below:

Internal Factors

• Controlled by gene expression and enzyme activity in metabolic pathways.

• Different plant organs produce varying amounts depending on developmental stage.

External Factors

• Light: The light environment, photoperiod, and quality alter levels of gibberellin involved in controlling such developmental events as flowering.

• Temperature: Fluctuations in temperature may alter the amount and activity, thus affecting growth rates.

• Water Availability: The biosynthesis and action of gibberellins occur optimally only when adequate water is available for plant growth.

Roles of Gibberellins In Plants

The function of gibberellin in plants is explained below:

Seed Germination

Gibberellins are plant hormones that are essential for the proper germination of seeds and play a very significant role in the initial phase of growth of a plant.

Mechanism

• Dormancy Break: Gibberellins stimulate the production of enzymes responsible for breaking seed reserves.

• Seedling Growth: They promote the growth of the embryo and initial seedling development.

Stem Elongation

Gibberellins play an important role in stem elongation and, hence, contribute to the height and general architecture of a plant.

• Cell Elongation and Division: They increase cell growth and cell division in stems, which leads to an increase in the height of the plant.

• Examples: Gibberellins are used to achieve optimum heights of crop plants, and the response is observed in both dwarf and tall cultivars.

Flowering And Fruiting

Gibberellins regulate reproductive growth, like induction of flowering and fruit development.

Effect

• Induction of Flowering: They induce flowering in plants under favourable conditions.

• Fruit Development: Gibberellins promote fruit size and uniformity.

Leaf And Root Growth

Gibberellins also influence the leaf and root growth, thus altering the overall growth patterns of the plants.

• Leaf Size: They may have an effect on leaf size and, thereby enhance the aesthetic value of the plants.

• Root Growth Patterns: They affect the pattern of root elongation and root branching.

Agricultural and Horticultural Applications

The details are given below:

Commercial Applications

Gibberellins have several commercial applications in agriculture and horticulture, all of which are oriented toward enhancing plant growth and productivity.

Crop Management

Gibberellins are used to control plant height, fruit size, and crop yields.

• Used to regulate plant height to prevent the lodging of cereal crops.

• Gibberellins help increase the size of fruits and thus improve the overall crop yield.

• Examples: Applied on crops like grapes and rice for better management of growth.

Gibberellin Inhibitors And Enhancers

Inhibitors and enhancers of gibberellins control the growth process and enhance the performance of the plants themselves.

Importance of Gibberellins in Plant Growth and Development

The importance of gibberellins in plant growth and development is:

• Regulate stage from embryo to adult stage.

• Coordinate reproductive organ development.

• Interact with auxins and cytokinins for balanced growth.

• Influence enzyme activity during germination and nutrient mobilization.

Gibberellin NEET MCQs (With Answers & Explanations)

Important topics for NEET are:

• Chemical and physical properties of gibberellins

• Regulation of Gibberellin production

Practice Questions for NEET

Q1. Bakanae disease is caused by

1. Fungus

2. Alga

3. Bacterium

4. Virus

Correct answer: 1) Fungus

Explanation:

Gibberella fujikuroi is the fungus that causes Bakanae sickness. Gibberellin, a substance produced by this fungus, causes rice plants to grow excessively tall. Lodging occurs when the plants wane and have the potential to topple down. In warm, humid weather, this disease primarily damages rice crops. It spreads via water, soil, and seeds. Infected plants develop poorly and have fading leaves. This illness may result in poorer yields for rice farmers. Bakanae disease can be avoided with proper maintenance and fungus control.

Hence, the correct answer is option 1) Fungus.

Q2. Foolish seedling disease of rice led to the discovery of

1. GA

2. ABA

3. 2, 4-D

4. IAA

Correct answer: 1) GA

Explanation:

Gibberellins (GA) were first observed from the fungus Gibberella fujikuroi, the causal organism of foolish seedling disease of rice plants in Japan by Kurosawa in 1926. Gibberellins are plant hormones that play a crucial role in growth and development, including seed germination, stem elongation, and flowering. They are now widely used in agriculture to promote growth and increase yields in various crops. The discovery of gibberellins has significantly advanced our understanding of plant physiology and hormonal regulation.

Hence, the correct answer is option 1) GA.

Q3. Select the incorrect match.

1. Indole compounds - Auxin

2. Terpenes - Ethylene

3. Adenine derivatives - Kinetin

4. Derivatives of carotenoids - ABA

Correct answer: 2) Terpenes - Ethylene

Explanation:

• Terpenes are a broad class of chemical molecules that are found in plants. They are made from isoprene units and have various uses like defence and scent.

• Ethylene is a gas hormone found in plants. It controls ripening, growth, and other functions. However, it is not a terpene.

Therefore, the match is inaccurate because terpenes and ethylene are two distinct plant chemicals.

Hence, the correct answer is option 2) Terpens - Ethylene.

Also Read:

• MCQs on Gibberellins

• Phases of Growth in Plants

• Auxin Biosynthesis

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