the role of light and growth regulators in seed germination
DESCRIPTION
This is about the role of phytohormones and light in the germination of seeds.TRANSCRIPT
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EXERCISE 17:
The Role of Light and Growth Regulators in Seed
Germination
GONZALES-MANOLONG-SOLIJON
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INTRODUCTION
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DORMANCY
• A temporary suspension of visible growth of any plant structure containing a meristem (Lang 1987).
• After embryo and endosperm development
• To initiate germination, three conditions must be met;
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1. Must be viable2. Must be subjected to appropriate environmental conditions3. Any primary dormancy must be removed
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• Light has been recognized around the mid-nineteenth century as a critical factor controlling germination (Crocker, 1930).
• The photochemically reactive pigment Phytochrome has been shown to be involved in the mechanism of light sensitivity in seeds (Bewley and Black, 1985).
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• When an imbibed seed is exposed to red light (600-760 nm) phytochrome (P) changes to Pfr
which promotes germination.
• When exposed to far-red light (760-800 nm), inhibits germination
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• Specific endogenous plant growth substances have important roles in the control of dormancy.
• Most of these are;– Abscisic Acid (ABA)– Gibberellinc Acid (GA)– Cytokinins– Others (Indoleacetic Acid, Kinetin, Auxin)
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OBJECTIVE
In this experiment the effect of light and certain growth regulators on seed germination will be investigated.
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MATERIALS AND
METHODS
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RESULTSAND
DISCUSSION
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TREATMENTS REPLICATE 1 REPLICATE 2
Germinatedseeds
Percent germination
Germinatedseeds
Percent germination
1.Dark (Control) 5 10% 4 8%2. White Light 4 8% 4 8%3. W/ GA3 + Dark 10 20% 10 20%4. w/ IAA + Dark 4 8% 1 2%5. w/ ABA + White 4 8% 1 2%6. Blue Light 0 0 0 07. Green Light 0 0 0 08. Red Light 8 16% 6 12%9. Infrared 1 2% 0 0
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Red light promotes germination
Phytochrome 660 Phytochrome 730(red absorbing) (far-red absorbing)
Far-red light inhibitsgermination
Figure 1. Effects of red and far-red light on the photochemically reactive pigment phytochrome and lettuce seed germinatio
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• The membranes of the seed coats and/or the endosperm act as light sensors; once removed light control disappears.
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4004104204304404504604704804905005105205305405505605705805906006106206306406506606706806907007107207307407500
10
20
30
40
50
60
Red Light
Wavelengths (nm)
Perc
ent t
rans
mitt
ance
(%)
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Red Light
4004104204304404504604704804905005105205305405505605705805906006106206306406506606706806907007107207307407500
5
10
15
20
25
30
35
40
45
50
Blue Light
Wavelengths (nm)
Perc
ent T
rans
mitt
ance
(%)
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4004104204304404504604704804905005105205305405505605705805906006106206306406506606706806907007107207307407500
10
20
30
40
50
60
Green Light
Wavelengths (nm)
Perc
ent T
rans
mitt
ance
(%)
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4004104204304404504604704804905005105205305405505605705805906006106206306406506606706806907007107207307407500
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Far-red Light
Wavelength (nm)
Perc
ent T
rans
mitt
ance
(%)
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