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FRSA
SEED ANALYSIS FACT SHEET :   GERMINATION AND DORMANCY

THE GERMINATION TEST

Germination is probably the single most convincing and accepted index of seed quality.  The exact procedures and regimes under which different kinds of seeds are germinated have been developed over 100 years of experience of experience in germination testing and have been augmented during the last 50 years by a systematic program of referee testing involving interchange of samples and results among laboratories.

AOSA  (Association of Official Seed Analysts) Rules for Testing Seed covers the following aspects of germination testing:

   1.    Generally use 400 seeds in four replications of 100 seeds each.  A minimum of 200 seeds can be used when double tests are done and for mixtures.
   2.    The pure seed or pure seed unit is used for the test.  The germination is directly affected by what is defined as pure seed.  AOSA rules define pure seed.
   3.    AOSA rules also provide the following species specific guidelines:
   a.    Substrate: examples are blotters, towels, kimpak, and sand.
   b.    Recommended temperatures in centigrade: frequently used temperatures are 20/30c alternating, 20c, 15c, constant.
   c.    Number of days in the test for maximum germination.
   d.    Additional instructions: KNO3, light (8 hours minimum), prechilling for certain number of days at 5c or 10c.
   4.    The interpretation of a normal seedling is based on written definitions and drawings of normal and abnormal seedlings for most kinds of seeds tested.


Reasons why seeds do not germinate:

DORMANCY

  causes:  physical, chemical, environmental, insufficient maturation
 
     1.  physical restraints
                  a.  seed coat, fruit coat
                  b. endosperm layer over radicle
     2.  chemical restraints
                  a.  hormones   examples:  GA, ethylene
                  b.  nutrients  example:  KNO3
     3.  environmental
                  a.  water and oxygen: too much or too little of either
                  b.    light:
   ·    some species light inhibited
         examples: Nemophila, Phacelia  (flower species
   ·    some species light promoted
         example: red light is needed for germination of grand rapids lettuce
                   c.    temperature/time:
   ·    prechill
   ·    alternating temperatures
   ·    constant temperatures too high or too low
     4.  maturity
       Some seeds have rudimentary,  basal or axile embryos: 
       In families: apiaceae, papaveraceae, ranunculaceae, liliaceae.  (onions, asparagus, carrots, buttercups, poppies, columbine).  Embryos need to grow and develop within the seed before they will germinate.


SEED DETERIORATION, DEATH, OR SEVERE IMMATURITY

      1.  Seed deterioration or death:
         
    a. pathogens: fungi, bacteria, virus, insects
    b. mechanical injury: improper handling, conditioning
    c. temperature (improper storage): heat or cold damage
    d. age: seed constituents break down, cells stop respiration

      2.  Severe immaturity: seed harvested too early, or essential tissues aborted (nutritive tissues or embryo). Insufficient nutrients or embryo development to support germination.

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