Plant Growth Regulation

Exercise 9

UY, MASA, JOSUE, DE LAYOLA, CORTEZ 10/10/12

INTRODUCTION

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

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

OBJECTIVES

• To be able to determine the effect of various hormones in plant growth

• To be able to monitor differences in plant responses

EFFECT OF AUXINON PLANTS

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.

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.

Results: Root Formation

VS

Results: Bud Formation in Stems

VS

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

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

Transport of auxin is polar.Sites of polar transport:

In coleoptiles: nonvascular tissuesIn shoots: vasular parenchymaIn the roots: xylem parenchyma (acropetal) or epidermal and cortical cells (basipetal)

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.

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.

EFFECT OF GIBBERELLIN

ON STEMS

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.

Results: Internodes Growth

VS

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 plantsStimulate stem growth in rosette plantsPromote seed germinationInvolvement in carbohydrate mobilizationPromote internodes elongation

Site of synthesis: developing seeds, developing fruits, young leaves, apical region

of rootsSynthesized via the mevalonic acid

pathwayNonpolar transport; moves in all direction

in the xylem and phloem

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.

EFFECT OF CYTOKININAND COCONUT ENDOSPERM

ON LEAF SENESCENCE

Methodology

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

Results: Root Formation

Petri dish treatment

Absorbance @645 (%)

Absorbance @663 (%)

Conc. 645

Conc. 663

Distilled water 2.322 2.336 0.042 0.027

Cytokinin

Coconut water 2.192 2.312 0.040 0.026

Cytokinin

First described by Johannes van OverbeekIt plays important roles in a number of plant activities, including:

Delaying leaf senescence Cell differentiationCell divisionPromotes lateral bud growth

Cytokinin works in tandem with auxin to cause cell morphogenesis and divisionIt is found in differentiating and meristematic parts of the plantTransport is non-polarSite of synthesis: root tipSynthesized by condensation of isopentenyl group group of DMPP with 6 nitrogen of ADP and ATP

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

ETHYLENEfrom apples

Methodology•Ge

t two healthy potted Coleus plants

•Place a cut apple in one pot

•Water plants and cover both in black plastic bags

•Leave for around 3 days

•Observe coloration differences and general appearances

•Using spectrophotometer obtain the chlorophyll content of leaves

ResultsChlorophyll content of leaves

Sample Chlorophyll concentration (umol/ml)

645 nm (Chl B) 663 nm (Chl A)

A (without ethylene)

2.83 2.94

B (with ethylene) 2.3 2.9

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 phenolicslike tannin

Ethylene

• Stimulates female flowering expression• Induces lateral cell expansion

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.

• Chlorophyllase breaks down chlorophyll• Can also control abscission depending on the

balance with auxin

EFFECT OF VARIOUS

GROWTH REGULATOR ON

SEED GERMINATION

METHODOLOGY

ABA

WATER

ABA

WATER

GA

ABA, CK, GACK GA,

CK

results

Treatment % germinationGA, dark 26.6CK, dark 95ABA, dark 0ABA, light 1.3GA, CK, dark 26.6GA, CK, ABA, dark 0H20, dark 95H20, light 98

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

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

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

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

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

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

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.

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

THE CONCLUSION

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

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