What is a Seed? We will learn more details later to answer this question. For now: Seed Coat: a surface tissue to keep seed dry inside Storage Tissue: could be a separate tissue (endosperm = inside seed) or part of the embryo (often cotyledons) Dormant Embryo: a small diploid plant with minimal metabolism (“suspended animation”)

Capsella Seed: Embryo Seed Coat Shoot Apex Endosperm Cotyledons - dicot Hypocotyl Radicle Root Apex Micropyle

Seed Germination: Water Warm Temperature Emergence of Radicle through Seed Coat Seeds lacking dormancy need: Water Warm Temperature So if you want to store seeds what are the conditions? Dry Cold Dormant seeds need more than moisture and warmth: Dormancy is caused by: Is overcome by: Example: nick digest scrub fire freeze-thaw cycles Thick Seed Coat Scarification Kentucky Coffee Tree or Thin Seed Coat Light Dark Lettuce Pea Insufficient Development Soil Fungus Association Orchids Inhibitor: Abscisic Acid Stratification > Vernalization Most CT feral plants 6 weeks at 4° C 20° C Inhibitor: Phenolics Leaching by Repeated Rain Cacti

Barley Seed Germination hydrolysis starch Fruit + Seed Coat maltose Endosperm sugar exocytosis Aleurone Layer cotyledon monocot -amylase Storage Protein translation hydrolysis shoot apex RNA Amino Acids growth Embryo DNA transcription GA radicle apex water imbibition

Lettuce Seed Germination Embryo phytochrome hydrolysis starch Seed Coat shoot apex sugar cotyledons -amylase dicot translation RNA growth transcription Embryo DNA radicle apex phytochrome photoreversibility red and white light stimulate germination 660 nm Pfr Pr water photoactivation 730 nm imbibition dark