Plant Growth Regulators (NEET aspect)

Описание: Plant Growth Regulators (PGRs) are organic substances (natural or synthetic) that control plant growth and development at very low concentrations. They are chemical substances that promote or inhibit plant growth.
Control processes like germination, flowering, fruiting, and dormancy.

There are five major plant growth regulators:
1. Auxins
First discovered PGR
Mainly produced in shoot tips
Functions:
Cell elongation
Apical dominance
Root initiation
Prevent premature fruit drop
Phototropism and geotropism
Example: IAA (Indole-3-acetic acid)

2. Gibberellins
First discovered from fungus Gibberella fujikuroi
Functions:
Stem elongation
Bolting (sudden elongation before flowering)
Increase fruit size
Promote malting in brewing industry
Example: GA₃ (Gibberellic acid)

3. Cytokinins
Promote cell division
Functions:
Cell division
Overcome apical dominance
Promote shoot formation
Example: Kinetin, Zeatin

4. Ethylene
Only gaseous plant hormone
Functions:
Fruit ripening
Leaf and fruit fall
Promote senescence
Break seed and bud dormancy

5. Abscisic Acid (ABA)
Growth inhibitor hormone
Also called stress hormone
Functions:
Induces dormancy in seeds and buds
Stomatal closure during water stress
Promotes leaf fall

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