1. Regulating Growth Plant Hormones
Plant Growth, Structure & Function
Regulating Growth Plant Hormones

2. Hormones
Hormones are organic substances produced in small amounts that regulate and coordinate metabolism, growth, and morphogenesis.

4. Plant Hormones: 5 Classes
Auxins
Young leaves, developing seeds.
Polar (unidirectionally) and nonpolarly.
Cytokinins
Root tips.
From roots to shoots via xylem.
Ethene
Most tissues in response to stress.
Diffusion from site of synthesis.
Abscisic acid
Mature leaves and roots, seeds.
From leaves in phloem and from the roots in the xylem.
Gibberellins
Young tissues of the shoot and developing seeds.
Xylem and phloem.

5. Auxin is the only plant hormone known to be transported polarly.
Polar transport is toward the base
Promotes cell elongation

6. Auxins Produces in the apical meristems at the tips of shoots
Auxin builds up on shaded sided of seedling and stimulates growth beneath the tip

7. Auxin Plays a Role in the Differentiation and Regeneration of Vascular Tissue

8. Auxin Promotes Fruit Development

9. Auxin Promotes the Formation of Lateral and Adventitious Roots

10. Synthetic Auxins - Herbicides

11. Ethene Plays a Role in Fruit Ripening

12. Ethene Promotes Leaf Drop
Ethene concentration increases and auxin concentration decreases in response to autumn’s shorter days and cooler temperatures

13. Cytokinins Promote Cell Division

14. Cytokinins Promote the Growth of Lateral Buds

15. Abscisic Acid (ABA)
ABA promotes seed dormancy and prevents early germination
ABA halts primary and secondary growth in plants
ABA acts as a stress hormone
ABA easily washes out during rainfall

16. Abscisic Acid is Responsible for Stomata Closure

17. Gibberellin (GA) Gibberellin (GA) causes dwarf mutants to grow tall.
Gibberellin causes hyperelongation of shoots by stimulating cell division and elongation.

18. Gibberellin Plays Multiple Roles 1) Breaking seed dormancy
2) In germination

19. Gibberellin Affects Fruit Development