Great Oaks from Little Acorns GrowIt all starts with a seed
I Can… Explain the process of seed germination.
I Will… • Describe conditions for
maintaining dormancy and promoting germination
• List the steps of seed germination
Seed Dormancy• Stasis prior to germination
• Metabolism falls
• Number of organelles per cell falls
• Dehydration – water content falls
• Vacuoles in cells deflate
• Food reserves become dense and
crystalline
Maintaining Dormancy• Physical barriers• Seed coat / Testa is waxy• Waterproof• Impermeable to oxygen
• Physical state – dehydrated• Chemical inhibitors present• Salts, mustard oils, organic acids,
alkaloids• Growth promoters absent
Seed Viability• Viability: When a seed is capable of
germinating after all necessary environmental conditions are met.
• Average life span of a seed is 10 – 15 years• Some very short-lived • e.g. willow (< 1 week)
• Some very long-lived• e.g. mimosa 221years
• Conditions important for longevity:• Cold, Dry, Anaerobic
• Conditions maintained in seed banks
Svalbard International Seed Vault• AKA – Doomsday Vault• 2008• Deep in the side of a frozen artic
mountain in Longyearbyen, Norway
Seed Germination – The breaking of dormancy; growth of embryo and its penetration of the seed coat.
Breakdown BarriersAbrasion of seed coat (soil particles)
Decomposition of seed coat (soil microbes, gut enzymes)Cracking of seed coat (fire)
Change in Physical StateRehydration
Destruction and Dilution of InhibitorsLight, temperature, water
Production of Growth Promoters
jump
Kopi Luwak ~Catgut coffee• Refers to the beans of coffee berries
once they have been eaten and excreted by the Asian Palm Civet
• Can sell for between $100 - $600 per pound
Back
Germination Steps:
1. Seed coat breaks down
2. Radicle becomes root3. Hypocotyl and
epicotyl become stem and growth tip
4. Plumule become first photosynthesis leaves
Great Oaks from Little Acorns GrowIt all starts with a seed
Learning Check:
Why does seed viability vary from just a week to hundreds of years in different plant species? Consider environmental factors in your answer.