Plant Growth Regulators: Types, Functions, and NEET Insights

Introduction

Plant Growth Regulators (PGRs) are organic compounds that influence physiological processes in plants. These are also called phytohormones and are essential for growth, development, dormancy, flowering, fruiting, and stress responses. For NEET aspirants, understanding PGRs is crucial as they frequently appear in exams.

---

Types of Plant Growth Regulators

1. Auxins

Discovered by F.W. Went.

Promote cell elongation, apical dominance, root initiation, and prevent premature fruit drop.

Example: Indole-3-acetic acid (IAA), NAA.

2. Gibberellins

Discovered from the fungus Gibberella fujikuroi.

Promote stem elongation, seed germination, and break dormancy.

Example: GA₃ (Gibberellic acid).

3. Cytokinins

Promote cell division, delay senescence, and stimulate lateral shoot growth.

Example: Kinetin, Zeatin.

4. Abscisic Acid (ABA)

Known as a stress hormone.

Induces seed dormancy, stomatal closure, and inhibits growth.

5. Ethylene

A gaseous hormone.

Promotes fruit ripening, leaf abscission, and flower senescence.

---

Functions in Plant Development

Apical Dominance – Controlled by auxins; removal of apical bud results in lateral growth.

Bolting – Elongation of internodes in plants like cabbage; promoted by gibberellins.

Parthenocarpy – Fruit development without fertilization; induced by auxins.

Senescence Delay – Cytokinins delay aging in leaves and fruits.

Dormancy Break – Gibberellins and cytokinins break seed and bud dormancy.

---

NEET Highlights

Match the following questions on PGRs are common.

MCQs on function-location-hormone associations are frequent.

Know scientists associated with the discovery of each hormone.

---

Conclusion

Plant Growth Regulators are vital for understanding plant physiology and have significant roles in agriculture and biotechnology. NEET students should focus on their types, functions, and associated experiments to score well in this unit.