Plant
Sciences
330
Spring 2000
Dr.
LeRoy Spilde
Lecture Notes:
Seed
Germination
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Definitions:
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Physiologist
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Seed analyst
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Agronomist
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Morphlogical Types
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Epigeal
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Hypocotyl elongates and raises cotyledons above the ground
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Typical of bean and pine seeds
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Hypogeal
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Storage organs remain below the ground
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Typical of the monocots, peas and several other species
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Requirements for Germination
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Maturity
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Proper balance between inhibitors and promotors
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Environmental factors
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Water
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Air
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Temperature
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Minimum min_temp.gif
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Alternating
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Commonly undomesticated species
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Typical of shallow emerging crops
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Stratification
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Chilling injury
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Light
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Intensity
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Quality
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Day length
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Influences on Light Sensitivity
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Age of seed
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Period of imbibition
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Imbibition temperature
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Stratification
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Germination temperature
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Pattern of Seed Germination
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Imbibition
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Controlled by:
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Chemical composition of the seed
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Seed coat permeability
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Water availability
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Enzyme activation
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Hydrolytic enzymes
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Synthesis of new materials
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Breakdown of storage tissues
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Carbohydrates
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Hydrolysis of amylopectin & amylose
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Glycolysis
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Krebs cycle
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Lipids
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Proteins
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Phospholipids
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Initiation of Embryo Growth
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Protrusion of the Radicle
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Seedling Establishment
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Geotropism
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Location of elongation among species
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Overall Changes During Germination
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Dry weight changes dw_germ.gif
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Transfer of carbohydrates, lipids and proteins
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Increases in nucleic acids
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Chemical Promotion
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Gibberellins
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Interaction with light and temperature
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Cytokinins
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Dormancy
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Transcription and translation
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Membrane permeability
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Ethylene
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Dormancy (auxin & gibberellin)
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Hydrogen Peroxide
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Auxins
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Potassium Nitrate
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Thiourea
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Other Chemicals
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Additional Factors
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Seed Quality
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Freedom from disease
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Size
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Density bd_germ.gif
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Color Color.gif
References:
Principles of Seed Science and Technology. 3rd Ed. L.O. Copeland and M.B.
McDonald. Chapman and Hill, New York, 1995