1. Controls of growth, development and movement
Plant Hormones
Controls of growth, development and movement

2. Processes in growth Cell division. Cell enlargment.
Cell differentiation.

3. Movement in Plants
Turgor movements (changes in turgor pressure in selected cells)
Growth movements (elongation of selected cells in response to stimulus)
phototropism
geotropism
thigmotropism

4. Turgor movement Mimosa pudica L. (sensitive plant)

5. Thigmotropism

6. Directional movements in response to a directional stimulus
Tropic responses
Directional movements in response to a directional stimulus

7. Growth movement

8. Phototropism

9. Geotropism

10. Hormones Signal molecules produced at specific locations.
Occur in low concentrations.
Cause altered processes in target cells at other locations.

11. Plant growth substances
Artificially synthesized substances which produce hormone like responses

12. General plant hormones
Auxins
Gibberellins
Cytokinins
Abscisic acid
Ethylene

13. Auxin

14. Auxin associated with phototropism - early experiments
demonstrate tip as receptor.

15. Demonstration of transported chemical

16. Auxin Discovered as substance associated with phototropic response.
Occurs in very low concentrations.
Differential response depending on dose.

17. Loosening of cell wall

18. Additional responses to auxin
abscission - loss of leaves
flower initiation
sex determination
fruit development

19. Gibberellin

20. Discovered in association with Foolish disease of rice (Gibberella fujikuroi)
uninfected
infected

21. Effects of Gibberellins
General cell elongation.
Breaking of dormancy.
Promotion of flowering.
Transport is non-polar, bidirectional producing general responses.

22. Cytokinins

23. Function of cytokinins
Promotes cell division.
Morphogenesis.
Lateral bud development.
Delay of senescence.
Stomatal opening.
Rapid transport in xylem stream.

24. Abscisic acid

25. Functions of abscisic acid
General growth inhibitor.
Causes stomatal closure.
Readily translocated.
Produced in response to stress.

26. Ethylene
H H
\ /
C = C
/ \

27. Functions of ethylene Gaseous in form. Rapid diffusion.
Affects adjacent individuals.
Fruit ripening.
Senescence and abscission.
Interference with auxin transport.
Initiation of stem elongation and bud development.