1. Plant Growth
Regulation
Exercise 9
UY, MASA, JOSUE, DE LAYOLA, CORTEZ 10/10/12

2. INTRODUCTION
• HORMONES - naturally occurring, organic
substances that at low concentrations exert a
profound influence in the physiological
processes.

3. INTRODUCTION
• Plant Hormones
– Site of synthesis is diffused
– Action at a distance is not an essential property
– Response can be dependent on the sensitivity of
the target cell
– Multiplicity effects
– Several hormones  one effect

4. OBJECTIVES
• To be able to determine the effect of various
hormones in plant growth
• To be able to monitor differences in plant
responses

5. EFFECT OF AUXIN
ON PLANTS

6. Methodology:Root Formation
Suspend short stem of Coleus and place in a
beaker with a part IAA and 10000 part water.
Label beaker then cover.
Place beaker in a sunny portion and observe
results after two weeks.

7. Methodology:Bud Formation
Remove leaf blades of one pair of leaves at a
node. Keep petiole intact.
Remove the shoot tip.
On one petiole apply lanolin paste on the
other apply lanolin with IAA.
Observe results after two weeks.

8. Results: Root Formation

9. Results: Bud Formation in Stems
VS

10. Indole-3-acetic Acid (a.k.a. Auxin)

11. Auxin
First described by Frits Went and first isolated by Kenneth
Thimann.
It plays important roles in a number of plant
activities, including:
leaf formation
phototropism
gravitropism
apical dominance
fruit development
abscission
root initiation and development
Development of the embryo

12. Transport of auxin is polar.
Sites of polar transport:
In coleoptiles: nonvascular tissues
In shoots: vasular parenchyma
In the roots: xylem parenchyma (acropetal) or
epidermal and cortical cells (basipetal)

13. Auxin stimulates adventitious root growth in
existing vascular tissues so that when they form they
can connect easily to the xylem and phloem.
Adventitious roots sometimes also originate in the
callus cells that form at the cut surface this is why it
possible to grow plants from stem cuttings.
Moreover, in high concentration of auxin enhances
adventitious root while inhibiting root elongation.

14. In shoots, auxin serves as lateral bud inhibitor meaning
presence of auxin in the stem would result to inhibition of
lateral bud formation instead of stimulating growth and
development.
Terminal shoots inhibits later bud growth which is termed
Apical dominance. Apical dominance is caused by the
downward transport of auxin produced in the apical
meristem.
Presence of auxin in cuts would result to inhibition of
lateral bud formation.

15. EFFECT OF
GIBBERELLIN
ON STEMS

16. Methodology:Stem Growth
Measure the internodes of one stem from the
tip to the fifth leaf downward using a potted
Coleus plant.
Add one drop of GA to the apical meristem
and place the plant in a sunlit area and water
regularly.
Measure the internodes of the plant after two
weeks.

17. Results: Internodes Growth

18. Gibberrellic Acid
Discovered by E. Kurosawa in 1926 through a
fungus in the genus Gibberrella.
Some of its physiological roles in a plant are:
Stimulate stem growth in dwarf plants
Stimulate stem growth in rosette plants
Promote seed germination
Involvement in carbohydrate mobilization
Promote internodes elongation

19. Site of synthesis: developing seeds,
developing fruits, young leaves, apical
region of roots
Synthesized via the mevalonic acid
pathway
Nonpolar transport; moves in all direction
in the xylem and phloem

20. Induce early production of seeds by some
biennials after only one season instead of two.
GA does not stimulate flowering in most
plants.
Addition of GA to embryoless seeds result in
the production of amylase and hydrolysis of
endosperm starch to sugar.

21. EFFECT OF CYTOKININ
AND COCONUT ENDOSPERM
ON LEAF SENESCENCE

22. Methodology
Make 9 leaf disks from mango leaves
Place 3 leaf disks in each of three petri dishes
On the first petri dish, add distilled water. Add
10% fresh coconut water on the second, and
cytokinin solution on the third
Change the solutions daily for 5 days
On the sixth day, add 4 ml acetone and extract
pigment. Check absorbance values for 663 and
664nm

23. Results: Root Formation
Petri dish Absorbance Absorbance Conc. Conc.
treatment @645 (%) @663 (%) 645 663
Distilled water 2.322 2.336 0.042 0.027
Cytokinin
Coconut water 2.192 2.312 0.040 0.026

24. Cytokinin
First described by Johannes van Overbeek
It plays important roles in a number of plant
activities, including:
Delaying leaf senescence
Cell differentiation
Cell division
Promotes lateral bud growth

25. Cytokinin works in tandem with auxin to cause cell
morphogenesis and division
It is found in differentiating and meristematic parts of
the plant
Transport is non-polar
Site of synthesis: root tip
Synthesized by condensation of isopentenyl group
group of DMPP with 6 nitrogen of ADP and ATP

26. Desiccation of the cells of the first set up was
uninhibited
For the other two set ups which have exogenous
supply of cytokinin, senescence was delayed
Coconut water has cytokinin which the seed uses
when it germinates

27. ETHYLENE
from apples

28. Methodology
• Get two healthy potted Coleus plants
• Place a cut apple in one pot
• Water plants and cover both in black
plastic bags

29. • Leave for around 3 days
• Observe coloration differences and
general appearances
• Using spectrophotometer obtain the
chlorophyll content of leaves

30. Results
Chlorophyll content of leaves
Sample Chlorophyll concentration (umol/ml)
645 nm (Chl B) 663 nm (Chl A)
A (without 2.83 2.94
ethylene)
B (with ethylene) 2.3 2.9

31. Ethylene
• Ripening fruit is a source of of ethylene
• Causes changes in fruit as it ripens
• Breakdown of chlorophyll, synthesis of other
pigments
• Softening due to cellulase and
pectinase
• Converts starch and acids to sugars
• Disappearance of phenolics
like tannin

32. Ethylene
• Stimulates female flowering expression
• Induces lateral cell expansion

33. Enhances rate of senescence
• Senescence is the programmed aging process
leading to death
• From genetic programming or hormonally
induced
• Aging is associated with the loss of chlorophyll
as leaves fade or turn brown.

34. • Chlorophyllase breaks down chlorophyll
• Can also control abscission depending on the
balance with auxin

35. EFFECT OF VARIOUS
GROWTH REGULATOR
ON
SEED GERMINATION

36. METHODOLOGY
WATER
WATER
ABA GA ABA
ABA, GA,
CK CK, GA CK

37. results
Treatment % germination
GA, dark 26.6
CK, dark 95
ABA, dark 0
ABA, light 1.3
GA, CK, dark 26.6
GA, CK, ABA, dark 0
H20, dark 95
H20, light 98

38. DISCUSSION
• Actions of GA, CK, and ABA are mediated
directly or indirectly via protein synthesis
(Fountain and Bewly, 1976)
• Gibberellic acid - the hormone that
promotes seed germination by initiating the
synthesis of amylase which the seeds require
to break down and hydrolyze endosperm to
sugar – their source of nutrition

39. DISCUSSION
• Cytokinin - promotes cell division and
morphogenesis of the seeds
• Abscisic Acid - the hormone t hat
regulates the germination of the
seed, signaling its maturity; ceases the growth
of the seeds, but serves as the sink for
nutrients

40. DISCUSSION
• Water: Light or Dark – requirement for
germination of lettuce seeds
– Control
• Lettuce seeds – require light and cool places
for its germination
– Therefore, light wins!
• Why dark?
– To isolate the sole reaction of seed germination
due to GA, CK and ABA without the aid of light
that might trigger other hormones

41. DISCUSSION
• ABA in Dark
– ABA: inhibitory hormone for seed germination
– Dark: not suitable location for lettuce seed
germination
– Therefore: least germination
• ABA in Light
– ABA: inhibitory hormone for seed germination
– Light: promotes germination of lettuce seed
– Therefore: relatively more % germination than
ABA in Dark

42. DISCUSSION
• GA in Dark
– GA: promotes seed germination by break down of
starch to glucose via generation of amylase
– Dark: not suitable location for lettuce seed
germination
• CK in Dark
– CK: promotes seed germination by cell division
and morphogenesis
– Dark: not suitable location for lettuce seed
germination
* Therefore: germination will still occur in both

43. DISCUSSION
• GA and CK in Dark
– GA: promotes seed germination by break down of
starch to glucose via generation of amylase
– CK: promotes seed germination by cell division
and morphogenesis
– Dark: not suitable location for lettuce seed
germination
– Both GA and CK promote seed germination
– Therefore: more % germination than in GA or CK
alone

44. DISCUSSION
• GA, CK and ABA in Dark
– GA: promotes seed germination by break down of
starch to glucose via generation of amylase
– CK: promotes seed germination by cell division and
morphogenesis
– ABA: inhibitory hormone for seed germination;
antagonistic to GA
– Dark: not suitable location for lettuce seed
germination
– GA and ABA cancel out, CK remains
– Therefore: there will still be % germination but less
than the GA and CK combined, and approximately
same as CK alone.

45. conclusion
• % germination:
Water in light > GA and CK in dark > GA in dark
= CK in dark = GA, CK, ABA in dark > ABA in
light > water in dark > ABA in dark

46. THE CONCLUSION

47. CONCLUSION
• To be able to determine the effect of various
hormones in plant growth
• IAA – promote adventitious root formation;
inhibits bud formation
• GA – promote elongation of stem internode
• CK – delay leaf senescence
• Ethylene – promote leaf abscission

48. CONCLUSION
• To be able to monitor differences in plant
responses
• As seen in the experiment, plant respond
differently to different hormones
– Formation of adventitious roots
– Inhibition of bud formation
– Elongation of internodes
– Leaf senescence and abscission
– Seed germination