QUESTION: Which of the following is not a plant hormone?
A Auxin
B Ascorbic acid
C Cytokinin
D Abscisic acid
ANSWER: Ascorbic acid
| Hormone | Chemical Formula | Origin | Function |
| Auxins | C₁₉H₂₂O₆ | · Apical meristem · Young leaves |
· Promotes cell elongation
· Controls root and shoot growth · Influences tropisms (phototropism, gravitropism) |
| Cytokinins | Various | · Root tips
· Developing fruits |
· Promotes cell division and differentiation
· Delays the process of aging · Influences apical dominance |
| Gibberellins | C₁₉H₂₂O₆ | · Young leaves
· Stems · Roots |
· Stimulates stem elongation
· Seed germination · Fruit growth · Breaks seed dormancy |
| Abscisic Acid | C₁₅H₂₀O₄ | · Leaves
· Stems · Roots |
· Induces dormancy and stress responses
· Inhibits growth · Regulates stomatal closure |
| Ethylene | C₂H₄ | · Various tissues | · Promotes fruit ripening and abscission
· Inhibits stem elongation · Influences senescence |
| Brassinosteroids | Various | · Pollen
· Young leaves · Stems |
· Promote cell elongation and division
· Enhance stress tolerance · Promote vascular differentiation |
| Jasmonates | C₁₂H₁₁NO₂ | · Wounded tissues
· Leaves |
· Mediate defense responses against herbivores and pathogens
· Regulate root growth |
| Salicylic Acid | C₇H₆O₃ | · Various tissues | · Induces systemic acquired resistance against pathogens
· Regulates plant defense |
| Strigolactones | Various | · Roots
· Root exudates |
· Suppress lateral bud growth
· Promote mycorrhizal associations · Inhibit shoot branching |
| Polyamines | Various | · Various tissues | · Involved in cell growth and differentiation
· Influence stress responses and flowering |