All plant growth hormone like auxins cytokinin IBA ethylene and all hormone that are used in agriculture and horticulture purpose and useful for agriculture students for presentation purpose

1. Chapter 5
BOT3015L
Regulation of Plant Growth by
Plant Hormones
Presentation created by Danielle Sherdan
All photos from Raven et al. Biology of Plants except when otherwise noted

2. • The 5 main groups of plant hormones
• Auxin
• Cytokinins
• Ethylene
• Abscisic Acid
• Gibberellins
• Brassica rapa, a model plant species for experimentation
• Design and begin group GA experiments
Today
• The 5 main groups of plant hormones
• Auxin
• Cytokinins
• Ethylene
• Abscisic Acid
• Gibberellins
• Brassica rapa, a model plant species for experimentation
• Design and begin group GA experiments

3. Hormones
Greek horman = to stimulate
Substance or chemical that is transported
and causes specific physiological effects
Although a topic throughout biology, in this course, we
will use plants as examples

4. Hormones in plants
• Hormones can have effects on the cells that produce
them and, after transport, at the target cells or tissues
• Hormones can have inhibitory rather than stimulatory
effects
• 5 main groups based on chemical structure

5. Auxin
Production
• Shoot tips
• Developing seeds
Some known actions
• Establishment of polarity of root-shoot axis during
embryogenesis
• Cell elongation
• Cell differentiation
• Apical dominance
• Lateral root formation and adventitious root formation
• Fruit formation

6. Under normal
conditions, shoot tips
bend towards the light
Without light on the
tip, no bending
When not at tip,
collar doesn’t
prevent bending
Conclusion: Light is sensed at the tip, but response not at tip
New hypothesis: A substance or chemical is transported
Auxin later isolated from shoot tips and
established to be involved in cell elongation
Drawings depicting seedlings of Zea (Gramineae family)
Darwins’ (Charles and son) experiment

7. High auxin
concentration
Low auxin
concentration
Drawings depicting Coleus (Lamiaceae family)
Evidence for the role of
auxin in apical dominance

8. Evidence for the role of auxin
in adventitious root formation
With synthetic auxin Without synthetic auxin
Saintpaulia (Gesneriaceae family)
Another example of misleading common name
The African violet is not in the violet family
Adventitious
roots growing
from stem
tissue

9. Evidence for the role of auxin in formation of fruit
and structures of similar function
(e.g. receptacle in strawberry)
Fragaria (Rosaceae family)
Band of achenes
removed
What do you expect?
Not shown: Auxin replacement restores normal fruit formation and can be
used commercially to produce seedless fruits
All achenes
removed
Normal
conditions
Without seed formation, fruits do not develop. Developing seeds are a
source of auxin.
However, too much auxin can kill the plant and thus synthetic auxins used
commercially as herbicides

10. Cytokinins
Production
• Primarily root tips
Some known actions
• Cell division (cytokinesis)
• Tissue culture
• Delay leaf senescence

11. Increasing auxin concentration
Increasing
Cytokinin
concentration
Auxin
promotes root
formation
Cytokinin promotes
shoot formation
Lack of
differentiation
when both are
present
Cytokinin and auxin
complexity of plant-hormone effects and interactions
Callus of Nicotiana
(Solanaceae family)

12. Cytokinin delays leaf senescence (ageing
and reabsorption of aged organs)
Transgenic Untreated
Genetic
modification to
increase
cytokinin
biosynthesis
Nicotiana (Solanaceae family)

13. Ethylene
Production
• In most tissues under stress, senescence, or ripening
Some known actions
• Fruit ripening
• Leaf and flower senescence
• Leaf and fruit abscission (controlled separation of
plant part from the main body)
• Floral sex determination in monoecious species,
promote female

14. Experimenting with plant response to ethylene
commercial uses
Mutated ethylene
receptor
Normal ethylene
receptor levels
Both are 100 days after picking
Lycopersicon (Solanaceae family)

15. Experimenting with plant response to ethylene
commercial uses
Mutated ethylene
receptor
Normal ethylene
receptor levels
8 days after pollination
Petunia (Solanaceae family)

16. Abscisic Acid (ABA)
Production
• Mature leaves, especially under stress
• Roots, then transported to shoots
Some known actions
• Stress response
• Stimulate stomatal closure
• Inhibit premature germination of seeds
• Embryogenesis
• Seed dormancy maintenance

17. ABA induces stomatal closure
a simplified diagram
Solutes (e.g. potassium and chloride
ions) accumulate in guard cells
causing water to accumulate in
guard cells, making them turgid
ABA is one signal that causes guard
cells to release solutes and thus
release water, making them flaccid and
closing the stoma (pore) between them
Guard cell response to ABA is one topic of research in the Outlaw lab at FSU
More about guard cells and experiments with guard cells
coming up in a couple of weeks

18. Gibberellins
Gibberellic acid (GA)
Production
• In young, developing shoots and seeds
Some known actions
• Cell division
• Cell elongation
• Stimulate seed germination
• Stimulate flowering
• Stimulate fruit development

19. Commercial use of GA
Thompson seedless grapes (Vitis (Vitaceae family)
Without GA With GA
Larger fruits that are easier to clean are
attractive in markets

20. What are the effects of GA on the
growth of Brassica rapa?
Why Brassica rapa?
Image from wikipedia.org

21. • The 5 main groups of plant hormones
• Auxin
• Cytokinins
• Ethylene
• Abscisic Acid
• Gibberellins
• Brassica rapa, a model plant species for experimentation
• Design and begin group GA experiments
Today

22. What are the effects of GA on the
growth of Brassica rapa?
Why Brassica rapa?
1. Many economically valuable plants in the (Brassicaceae family)
Broccoli, cabbage, cauliflower, kale, radish, mustard, Canola oil
2. Members of the Brassicaceae family have become
model plant species. Some characteristics that are
important for model species include:
• Relatively small genome
• Easy to grow
• Rapid life cycle
• Broadly and thoroughly studied
• Not atypical
• Genetic tools available
See also Outlaw lecture notes
and footnotes for more about
Brassicas and model species

23. What are the effects of GA on the
growth of Brassica rapa?
Production
• In young, developing shoots and seeds
Some known actions
• Cell division
• Cell elongation
• Stimulate seed germination
• Stimulate flowering
• Stimulate fruit development
What do you expect?
What are your hypotheses?

24. How would you design an
experiment?
Question: What are the effects of GA on the growth
of Brassica rapa?
Some of the materials available:
• Seeds of normal (wild-type, WT) Brassica rapa
• Seeds of Brassica rapa that produce less GA than normal (rosette, (ROS))
• Materials for planting and growing plants in the greenhouse at Conradi
• The following GA solutions:
• 0 M
• 3 M
• 30 M
For the other materials that your design requires, please discuss with TA

25. Aspects of good experimental design
Detailed step-by-step plan
How much?
How many?
What kind?
How long?
When?
Where?
Read about guidelines in lab manual
Repetition - general or exception
Control conditions in which the outcome is predictable

26. Data collection and presentation
The following must be on your group data sheet along with
all of the group members’ names
“Official Group Datum Sheet for GA Experiment”
This datum record will remain by the experimental plants and all
measurements will be recorded on this sheet and in individual’s
lab notebook when the measurements are taken. These
measurements will be provided to group members for the
preparation of each’s individual GA report
Be sure to read the class policy, Academic Honor Policy,
and lab manual (chpt 5) for information regarding group
experiments and data collection
The experimental design, execution, and the report are
worth 15% of your grade

27. Turn in…
• Experimental design
• Datum sheet
• Schedule for experiment
• Contact info for each group member
distributed to all group members
Then: To Conradi for planting