Gibberellins are important plant hormones that play a crucial role in various growth and developmental processes. These hormones, known for promoting stem elongation, seed germination, and flowering, are essential for optimal plant health. Understanding gibberellins can enhance agricultural practices by improving crop yield and quality. Explore into the functions and significance of gibberellins to uncover their impact on plant biology and agricultural advancements.

What are Gibberellins?

Gibberellin is a phytohormone that is involved in growth promotion. Gibberellins have been found in hundreds of species, including fungi and higher plants. Produced in the chloroplasts via the terpenoid pathway, they are transported to the endoplasmic reticulum and cytoplasm after production, until their biological activation. More then 70 types of giberllins are present. GA3 is a extensively researched plant growth regulator.

Historical Discovery of Gibberellins

Gibberellins were first discovered in the 1920s by Japanese scientist Eiichi Kurosawa while studying “bakanae” or foolish seedling disease in rice, caused by the fungus Gibberella fujikuroi. Subsequent research identified gibberellins as the growth-promoting compounds produced by the fungus, leading to the understanding of their role in plant development.

Structure of Gibberellins

Numerous areas of the plant produce distinct forms of gibberellin molecules. There are currently more than 100 distinct gibberellin molecules. These chemicals are produced by the plant in a variety of cell types, although they tend to accumulate in the roots. As opposed to auxin, which concentrates at the apex, this is different. Gibberellin is a diterpenoid, a well-known and frequently occurring chemical in biochemistry. It serves as the building block for compounds like vitamins A and E. Below is the structure of gibberellin A1, also regarded as the first found gibberellin:

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The side-groups vary in each gibberellin, while the rest of the structure remains the same. The functions are determined by these side groups.

Gibberellins Functions

The plant hormone is responsible for a variety of functions, as mentioned below:

• Seed Germination: Sunlight is a major component for germinating seeds of several species. In its absence, those seeds fail to germinate in time. However, the requirement of sunlight can be replaced by gibberellins, which can facilitate the fast germination of those seeds.
• Dormancy in Buds: Often buds are dormant i.e. they don’t grow due to several reasons (eg. lack of ideal conditions). Gibberellins can trigger the breaking of such dormancy in buds.
• Postponing aging: Gibberellins can postpone the senescence (aging) of leaves and other plant components, keeping them functioning and green for extended periods.
• Elongation of Stem: Gibberellins encourage cell proliferation and elongation in the internodes of the stem, which in turn promotes stem elongation. This has an impact on the plant’s total height and the distance between its branches and leaves.
• Development of Fruits: The phytohormones can heavily influence the size and growth of fruits. They may, in certain instances, cause the fruit to elongate and the reduction of seed production.

Mechanism of Action

Gibberellins (GAs) act through a complex signaling pathway to regulate plant growth and development. When gibberellins bind to their receptor, GID1, this complex interacts with DELLA proteins, which are growth repressors. The binding triggers the degradation of DELLA proteins via the ubiquitin-proteasome pathway, relieving their inhibition on growth-promoting genes. This degradation allows for the transcription of GA-responsive genes, promoting processes such as stem elongation, seed germination, and flowering. The precise regulation of this pathway ensures that plants can adapt their growth in response to internal signals and environmental cues, optimizing their development and reproductive success.

Uses of Gibberellin

Considered to have a main role in driving the green revolution, gibberellin finds its use in a wide range of applications as listed below:

• Gibberellins are employed in the brewery sector to encourage uniform growth of barley throughout the malting process, leading to grains with consistent enzyme activity and starch content.
• Gibberellins are compounds that are utilized in tissue culture procedures to promote the growth of plantlets from explants and the lengthening of shoots. This is critical for the quick multiplication of plant propagation material.
• Gibberellins can lengthen stems and enhance cut flower quality, making them more desirable to the florist business. The making of cut roses and bouquets is a frequent example of this.

Agricultural Applications of Gibberellins

• Gibberellins promote stem elongation, leading to taller and more robust plants.
• They break seed dormancy, hastening germination and ensuring uniform crop establishment.
• Gibberellins enhance fruit size and quality in crops like grapes, apples, and citrus.
• They regulate flowering time, ensuring synchronized blooming and fruit set in crops such as rice and wheat.
• Gibberellins induce parthenocarpic fruit development, leading to seedless varieties.
• In horticulture, gibberellins are used to produce ornamental plants with desired traits like elongated stems or enhanced flowering.

Conclusion: Gibberellins

In conclusion, gibberellins are essential plant hormones with diverse roles in growth and development. From promoting stem elongation to enhancing fruit quality, their agricultural applications are profound. Understanding gibberellin mechanisms offers promising avenues for optimizing crop yield, quality, and overall agricultural productivity.

Also Read:

• Difference Between Auxin and Gibberellin
• Physiological Effects Of Plant Growth Regulators
• Auxin
• Coordination in Plants

FAQs on Gibberellins

Who made the Initial Discovery of Gibberellins?

Elichi Kurosawa, a Japanese scientist, discovered gibberellin in 1926 while researching bakane, often known as the “foolish seedling disease” of rice.

How to Describe the Chemical Nature of Gibberellins?

Gibberellins are acidic. It aids in the cell’s expansion and lengthening because of its acidic composition.

How is Gibberellin Transported in Plants?

Generally, they are transported via phloem (though xylem transport is also possible), similar to other organic compounds.

How are Gibberellins Activated?

Water intake stimulates gibberellins, which subsequently signal the transcription of the gene-producing amylase, a metabolic enzyme that converts starches stored inside the seed into simple sugars.

Which is the Antagonist of Gibberellin?

Abscisic acid is a well-known antagonist, promoting seed dormancy, unlike gibberellins which promote germination.

What are the Effects of Gibberellins on Plants?

The primary effects of gibberellins on plants includes breaking seed dormancy, making the plants to grow and contribute to its overall development.

What are the Uses of Gibberellins?

Gibberellins play major role in agriculture due to its property of accelerating seed germination and ensuring that fruit yield is uniform. Besides that, it is also used for plant breeding and tissue culture.

What is the Role of Gibberellins in Flowering?

Gibberellins helps plants to jump from the vegetative to the reproductive phase. Also it is helpful for daylength flowers, where sunlight is necessary for flowering.