• Definitions:
  1. Physiologist
  2. Seed analyst
  3. Agronomist

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• Morphlogical Types
  • Epigeal
    • Hypocotyl elongates and raises cotyledons above the ground
    • Typical of bean and pine seeds
  • Hypogeal
    • Storage organs remain below the ground
    • Typical of the monocots, peas and several other species

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• Requirements for Germination
  • Maturity
  • Proper balance between inhibitors and promotors
  • Environmental factors
    • Water
    • Air
    • Temperature
      • Minimum min_temp.gif
        • Applies to all crops
      • Alternating
        • Commonly undomesticated species
        • Typical of shallow emerging crops
      • Stratification
      • Chilling injury
    • Light
      • Intensity
      • Quality
      • Day length
  • Influences on Light Sensitivity
    • Age of seed
    • Period of imbibition
    • Imbibition temperature
    • Stratification
    • Germination temperature

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• Pattern of Seed Germination
  • Imbibition
    • Controlled by:
      • Chemical composition of the seed
      • Seed coat permeability
      • Water availability
  • Enzyme activation
    • Hydrolytic enzymes
    • Synthesis of new materials
  • Breakdown of storage tissues
    • Carbohydrates
      • Hydrolysis of amylopectin & amylose
      • Glycolysis
      • Krebs cycle
    • Lipids
      • Oxidation processes
    • Proteins
      • Proteolytic enzymes
    • Phospholipids
  • Initiation of Embryo Growth
  • Protrusion of the Radicle

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• Seedling Establishment
  • Geotropism
  • Location of elongation among species

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• Overall Changes During Germination
  • Dry weight changes dw_germ.gif
  • Transfer of carbohydrates, lipids and proteins
  • Increases in nucleic acids

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• Chemical Promotion
  • Gibberellins
    • Interaction with light and temperature
  • Cytokinins
    • Dormancy
    • Transcription and translation
    • Membrane permeability
  • Ethylene
    • Dormancy (auxin & gibberellin)
  • Hydrogen Peroxide
    • Respiration
    • Diseases
  • Auxins
    • Light
  • Potassium Nitrate
    • Light kno_lgt.gif
  • Thiourea
    • Light
    • Temperature
  • Other Chemicals

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• Additional Factors
  • Osmotic Pressure
  • pH
  • Osmoconditioning osmo_ger.gif
  • Pre-harvest seed injury
    • Temperature ger_temp.gif
    • Moisture
    • Mechanical injury md_germ.gif
    • Genotype
  • Radiation micr_ger.gif
• Seed Quality
  • Freedom from disease
  • Size
  • Density bd_germ.gif
  • 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