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15 Cards in this Set

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How do seeds form in Angiosperms?
After fertilization, the plant embryo grows & develops

Once meristems and cotyledons (seed leaves) differentiate, development stops (or, the embryo becomes dormant)

Outer layers of the ovule develop into a relatively impermeable seed coat, enclosing the dormant embryo and endosperm (stored food)

Mature seeds contain between 5% - 20% water
Adaptive Importance of Seeds
Postpone development until favorable conditions are present

Afford maximum protection to the young plant at its most vulnerable stage of development

Contain stored food permitting development before photosynthesis starts (Endosperm)

Have specific dispersal mechanisms, facilitating migration of alleles into new gene pools
Cotyledons
seed leaves
Male reprodutive site
stamen
sperm are made in anther
Female reproductive site
pistel which contains ovary
How do fruits form?
Fruits are mature ovaries
Dry fruits
follicles, legumes, samaras, nuts, grains
Fleshy fruits
drupes, berries, hesperidia, pomes, pepos
Aggregate fruits
develop from many ovaries of a single flower

strawberries, blackberries
Multiple fruits
develop from a cluster of flowers

pineapple, mullberry
Methods of Seed dispersal via fruit (w/ example)
Birds – fruits with fleshy coverings, usually shiny black, blue, or red

Mammals
- fruits with hooked spines that attach to fur
- fruits buried by squirrels or other mammals (nuts)

Wind – maples, elms, dandelions, cottonwoods, etc.

Water – beach plants (like coconuts)
Germination: Definition
The resumption of growth and development by a spore or seed
Germination: Conditions Necessary
Only occurs when water is absorbed, which breaks the seed coat

Sufficient oxygen must be present for development to continue

Thus very few types of seeds can germinate under water
Germination: Process at start
Cellular respiration resumes, using oxygen & food stored in seed

Roots emerge first, then cotyledons
Hypocotyl
connects root system to cotyledons