Seed Characteristics Plant Propagation

3 Basic Parts Embryo Food Storage Tissues Coverings

Embryo Living part of the seed. Produced by the fusion of male and female gametes.

Young Seedling Epicotyl: means “above the cotyledons”. It becomes the above-ground shoot. Hypocotyl: means “below the cotyledons”. It becomes the below-ground root system.

Epigeous vs. Hypogeous Germination Epigeous Germination Hypogeous Germination Cotyledons First true leaves

Food Storage Tissues Endosperm in monocots. Cotyledons in dicots.

Coverings Seed coat ( formed from integuments). In some cases the Pericarp (ovary wall).

Sunflower Seed

Germination Requirements of Seed Moisture Favorable temperatures Oxygen

Light and Seed Germination May be required for germination in some species: Small-seeded annual plants Photo-dormant weed seeds

Seed Dormancy A seed is said to be dormant when it is unable to germinate even though the proper conditions for germination are all present.

Viable vs. Non-viable Seed Viable: the embryo is alive and capable of germinating. Non-viable: the embryo is dead and cannot germinate.

Viability Tests #1 Place the seed in a bucket of water. #2 Tetrazolium test. #3 Cut test. #4 Germination test.

Seeds Treated with Tetrazolium

Stages of Seed Germination #1 Activation #2 Nutrient digestion and translocation #3 Seedling growth

Activation Imbibition of water – physical process Increased enzyme activity Cell elongation/enlargement Radicle emergence

Radicle Emergence in Corn Corn Seed Radicle

Nutrient Digestion and Translocation Stored food converted from starches to simpler forms (sugars). Sugars absorbed by cotyledons and translocated to the embryo.

Seedling Growth Epicotyl emergence. Continued development of the radicle.

Seed Provenance Refers to the geographical region from which the seed is collected. Cold hardiness Growth rate Drought tolerance, etc… USDA Forest Service “Super Trees”.

The End