Slide 1: Introduction Welcome to our presentation on Gibberellins, a group of plant hormones that play a crucial role in regulating various aspects of plant growth and development. Today, we'll explore the fascinating world of Gibberellins and their impact on plant physiology and agriculture. Slide 2: What are Gibberellins? Gibberellins are a class of plant hormones that regulate several developmental processes, including seed germination, stem elongation, flowering, and fruit development. They were first discovered in the 20th century in studies of a fungal disease called "foolish seedling" in rice plants. Slide 3: Biosynthesis of Gibberellins Gibberellins are synthesized in various plant tissues, including young leaves, shoot tips, and developing seeds. The biosynthetic pathway involves several enzymes and precursor molecules, with different Gibberellin forms produced depending on the specific pathway and plant species. Slide 4: Physiological Effects of Gibberellins Gibberellins have diverse effects on plant growth and development, including promoting stem elongation, inducing flowering, breaking seed dormancy, and stimulating fruit development. They also influence cell division and expansion, leaf expansion, and responses to environmental stimuli such as light and temperature. Slide 5: Gibberellins in Seed Germination Gibberellins play a crucial role in breaking seed dormancy and promoting seed germination. They stimulate the production of enzymes that degrade seed coat tissues and mobilize stored nutrients, allowing the embryo to emerge and initiate growth. Slide 6: Gibberellins in Stem Elongation Gibberellins are key regulators of stem elongation, particularly in dicotyledonous plants. They promote cell division and expansion in the stem, leading to increased internode length and overall plant height. Slide 7: Gibberellins and Flowering Gibberellins influence the transition from vegetative to reproductive growth and regulate the timing of flowering in many plant species. They interact with other hormonal pathways and environmental signals to coordinate flowering initiation and development. Slide 8: Applications of Gibberellins in Agriculture Gibberellins have numerous applications in agriculture, including promoting fruit development, improving crop yield, and managing plant growth. They are used in horticulture to induce flowering, enhance fruit size, and increase crop uniformity. Slide 9: Challenges and Limitations Despite their many benefits, Gibberellins also pose challenges, such as potential side effects on plant physiology and the environment. Proper dosage and timing of Gibberellin application are critical to avoid undesirable effects and optimize agricultural outcomes. Slide 10: Future Directions and Research Ongoing research continues to unravel the complexities of Gibberellin signaling and its interactions with other hormonal pathways.

1. Gibberellins
Name : Anjani Kumari
Semester : 2nd Sem , PG
University Roll No. : 2420891010003
Class Roll No. : 06

2. Introduction
Gibberellins, a class of plant hormones, profoundly
influence growth and development processes in
plants. First discovered in the 20th century, these
compounds play pivotal roles in various physiological
responses, including seed germination, stem
elongation, flowering, and fruit development.
Gibberellins interact with specific receptors in plant
cells, triggering cascades of biochemical reactions that
regulate gene expression and cellular functions.
Understanding their mechanisms promises
advancements in both agricultural practices and
fundamental plant biology.

3. Discovery of Gibberellins
Gibberellins, plant hormones crucial for growth and
development, were discovered in the 20th century.
In the 1920s, Japanese scientists noticed an abnormal
elongation in rice plants infected with a fungus,
Gibberella fujikuroi, leading to the term "gibberellin."
In 1935, Yabuta and Sumiki isolated a compound
responsible for this elongation, named gibberellin A1.
Later, additional gibberellins were identified, showing
diverse effects on plant physiology, including stem
elongation, seed germination, and flowering.
Their discovery revolutionized agriculture, enabling
control over plant growth processes, leading to
enhanced crop yields and the development of dwarf
varieties for more efficient farming practices.

4. Plants Harmones

5. Plants Harmones

6. Chemical structure of Gibberellins
Gibberellins are a group of plant hormones
characterized by their tetracyclic diterpenoid
structure, consisting of a gibberellin skeleton
formed by four fused rings (A, B, C, and D).
The basic structure includes three six-
membered rings and one five-membered
ring. The gibberellin molecule typically
contains numerous hydroxyl and carboxyl
functional groups attached to the rings,
which contribute to its biological activity and
chemical diversity.

7. Gibberellin Biosynthesis : Three
Stages

8. Gibberellin Biosynthesis : Three
Stages
• Gibberellins are diterpenoid acids that
are synthesized in plastids through the
terpenoid pathway. The biosynthesis of
gibberellins (GAs) in higher plants can
be divided into three stages:
• Biosynthesis of ent-kaurene in
proplastids.
• Conversion of ent-kaurene to GA12 via
microsomal cytochrome P450
monooxygenases
• Formation of C20- and C19-GAs in the
cytoplasm

9. Role and impact of gibberellins
Gibberellins play a pivotal role in various aspects of plant growth
and development, exerting a profound impact on plant
physiology.
1. Stem Elongation
2. Seed Germination
3. Flowering
4. Fruit Development:
5. Leaf Expansion:
6. Bolting
7. Tuber Formation
However, excessive gibberellin application can lead to
undesirable effects such as lodging in cereal crops or excessive
vegetative growth. Thus, understanding the precise roles and
dosages of gibberellins is crucial for optimizing their use in
agriculture while minimizing negative consequences.

10. • Produce commercially from Fungal Culture
• Promote Cell Enlargement in the presence of
Auxin.
• Promote Cell Division in Apical Meristem of
Cambium.
• Promote bud Initiation in shoot of
Chrysanthemum Callus.
• Promote leaf growth & Fruit growth
• Induce Parthenocarpy
Role and impact of gibberellins

11. Role and impact of gibberellins
• In apical dominance, Enhance action
of auxins.
• Break bud and seed dormancy
• Sometimes substitute for red light
• Promote Flowering in long day plants
• Inhibits in short day Plants
• Cause delay in leaf senescence in a
few species

12. Use of Gibberellins in Agriculture
• The use of gibberellins (GAs) in agriculture has
significantly influenced crop production and
management practices. Here are some key applications
of gibberellins in agriculture:
• Seed Germination:
• Fruit Set and Development
• Stem Elongation and Lodging Prevention
• Fruit Ripening and Shelf Life Extension
• Seedless Fruit Production
• Promotion of Flowering

13. Environmental factors affecting
Gibberellins Activity
Gibberellin activity in plants is influenced by
various environmental factors, which can
modulate gibberellin biosynthesis, metabolism,
and signaling pathways. Here are some key
environmental factors that affect gibberellin
activity:
Light
Temperature
Water Availability
Nutrient Availability
Oxygen Levels
Biotic Stress

14. Future Directions in Gibberellin
Research
Future research in gibberellin biology is likely to explore
several key areas to deepen our understanding of these plant
hormones and their applications. Here are some potential
directions for future gibberellin research:
• Molecular Mechanisms
• Genetic Regulation
• Environmental Responses
• Crop Improvement
• Biotechnological Applications
• Ecological Impacts
• Drug Discovery

15. Challenges and Limitations
Despite the significant progress made in
understanding gibberellin biology, several challenges
and limitations remain in this field of research. Here
are some key challenges and limitations:
• Gibberellin signaling pathways are highly complex
• Environmental Factors Influence gibberellin activity.
• Environmental factors such as light, temperature,
water availability, and nutrient status influence
gibberellin activity and plant growth responses
• Manipulating gibberellin signaling in agricultural
systems may have unintended ecological
consequences
• Limitation of Technology to completely harness it.

16. Conclusion
Understanding the complex interactions between
gibberellins, other hormones, and environmental factors is
crucial for harnessing their potential to enhance crop
productivity sustainably. Addressing these challenges
requires interdisciplinary collaboration, innovative
technologies, and ethical considerations to ensure the
responsible use of gibberellins in agriculture.
By overcoming these hurdles, we can unlock new
opportunities to improve food security, mitigate
environmental impacts, and promote the well-being of
both ecosystems and society.

17. Thank You