Seed Dormancy

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Seed Dormancy

• By Drew Mutlick, Erin Milligan, Mark Mullin

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What is seed dormancy?

• Seed dormancy means to delay germination until
  favorable environmental conditions are present
  for seed germination and sprout growth.

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What is seed germination?

• The growth and development from seed to a plant.

http//www.pssc.ttu.edu/plantprop/lecnotes/section
2/topic7.htm
http//sps.k12.ar.us/massengale/images/dicotseedli
ng.jpg
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Types of Dormancy

• Primary dormancy delays initial seed germination.
• There are six kinds of primary dormancy.

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Primary Dormancy

• Seed coat physical dormancy is when the seed
  coat prevents the seed from absorbing water
• Seed coat mechanical dormancy is when the seed
  coat prevents the embryo from breaking through.
• Chemical dormancy is when chemicals within the
  seed coat prevent the seed from germinating.

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Primary Dormancy

• Morphological dormancy is when the seed has not
  completed at the time the seed leaves the plant
• Physiological or Intermediate dormancy occurs
  because a physiological condition is not being
  met.
• Deep dormancy is when plants stay dormant until
  favorable conditions are met, usually involving a
  period of cooling.

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Primary Dormancy

• Double dormancy is the combination of any of the
  previously mentioned factors.

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Secondary Dormancy

• Secondary dormancy prevents the seed from
  germinating after it absorbs water.
• Is caused by temperature extremes, prolonged
  darkness, prolonged light, water stress, or
  oxygen extremes.

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Example of Seed Coat Dormancy - Physical

• Rhus aromatica Fragrant Sumac
• The seed coat becomes impermeable to water after
  maturation to survive the winter.
• Broken when the seed coat is disrupted or
  dislodged by environmental factors

http//www.nps.gov/.../Shrubs/Rhus-aromatica-1-RHW
.jpg
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Example of Seed Coat Dormancy - Mechanical

• Pistacia vera L., Anacardiaceae Pistachio Nut
• The hard lignified shell is too thick for the
  radical to break through.

http//www.batcon.org/batsmag/images/v19n4c.jpg
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Example of Chemical Dormancy

• Grevillea eriostachya Grevillea
• Smoke from woody vegetative materials activates
  germination.

http//florabase.calm.wa.gov.au/.../timage/2001ic1
.jpg
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Example of Morphological Dormancy

• Ranunculaceae The Buttercup Family
• The seeds complete their maturation after leaving
  the plant

www.digitalnaturalhistory.com/ranunculus.jpg
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Example of Physiological or Intermediate Dormancy

• Echinacea purpurea Purple Coneflower
• Purple Coneflower requires a specific temperature
  range to germinate.

http//www.cambridge2000.com/gallery/html/P7051461
2e.html
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Example of Deep Dormancy

• Rubus spp. Raspberry
• Raspberries can last in the seed bank until the
  soil is exposed to open sky or is disturbed.

http//www.colorado.edu/.../foods/raspberry.gif
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Example of Double Dormancy

• Grevillea eriostachya Grevillea
• Grevillea is also physiologically dormant due its
  dependence on the chemical properties of soil
  after a fire.

http//users.bigpond.net.au/macarthuraps/Grevillea
20eriostachya2.jpg
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Example of Secondary Dormancy

• Chenopodium bonus-henricus - Good King Henry
• Chenopodium requires a slight chill or direct
  exposure to light to germinate after absorption
  of water.

http//pharm1.pharmazie.uni-greifswald.de/systemat
ik/7_bilder/pios/pio00252.jpg
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Sources

• http//www.pssc.ttu.edu/plantprop/lecnotes/section
  2/topic7.htm
• http//www.ces.ncsu.edu/depts/hort/hil/hil-8704.ht
  ml
• http//4e.plantphys.net/article.php?chtid8
• http//trc.ucdavis.edu/egsutter/plb171/lecturespdf
  4/5-Seed20dormancy02.pdf
• http//www.csrees.usda.gov/funding/nri/highlights/
  2002_no7.pdfSeedDormancyhlenctclnkcd13gl
  us
• http//www.uky.edu/Projects/SeedBiology/DORMANCY.H
  TM
• http//www.passionflow.co.uk/downloads/seed2520do
  rmancy25201997.pdfSeedDormancyhlenctclnkcd
  17glus
• http//www.batcon.org/batsmag/images/v19n4c.jpg
• http//www.nps.gov/.../Shrubs/Rhus-aromatica-1-RHW
  .jpg
• http//www.florabase.calm.wa.gov.au/.../timage/200
  1ic1.jpg
• http//www.cambridge2000.com/gallery/html/P7051461
  2e.html
• http//www.digitalnaturalhistory.com/ranunculus.jp
  g
• http//www.colorado.edu/.../foods/raspberry.gif
• http//users.bigpond.net.au/macarthuraps/Grevillea
  20eriostachya2.jpg
• http//sps.k12.ar.us/massengale/images/dicotseedli
  ng.jpg