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.