Plant Reproduction - Biology 35

Germination of Seeds

Germination of Seeds

after seeds are formed, they dehydrate and enter a period of dormancy until favourable conditions exist, at which time germination will occur

Embryo

develops plant from within seed

Cotyledon

embryonic leaf in a seed (not a true lead); food storage site for developing embryo

Testa

seed coat; outer, productive layer covering the seeds

Micropyle

small pore in a seed allowing water to enter

embryo shoot(hypocotyl)

embryonic stem; above embryonic root

embryo shoot (radicle)

will become the root of the plant

Seed germination conditions

• water to rehydrate seed tissues

• warmth for biochemical reactions to occur

• oxygen to allow cellular respiration to occur producing atp for energy

Angiosperm Growth

flowering plants; includes all plants except conifers, ferns, and mosses

angiosperms coevolved with insects and birds that pollinate them, making them co-dependent

• reproduction occurs in flowers making offspring of seeds

Tissues of Angiospermophytes

Mutualism

both species in a relationship benefit from an interaction

Example of mutualism

• animal pollinators get nectar and pollen from plant as food source

• plant gets safe and reliable transport of pollen from one flower to another

Fertilization

process by which sperm nucleus of pollen unites with ovule(egg) in ovary

seed dispersal (+examples)

embyro is dispersed to different locations

• through wind (milkweed, dandelion, maple)

• through animals (beggar0ticks, sandbur, blackberries)

• through water (lotus, cattail, coconut)

• by bursting (violet jewelweed, witch hazel)

• through humans (beans, wheat, cherries)

Photoperiodism

response of a plant to each amount of light or darkness it is exposed to each day; amount of uninterrupted darkness determines formation of flowers on most types of plants

Long-day plants

blooms in summer when nights are short (i.e. radish)

Short-day plants

blooms in early sprint and autumn when nights are long (i.e. chrysanthemum)

• when leaves are exposed to >12h of darkness, florigen-FT(a hormone) is stimulated to the shoot apex

Day-neutral plants

Blooms without regard to light or darkness (i.e. dandelion)

Beginning of flower production

At the shoot apical meristem, the hormone enters the cells and activates floral genes. This induces the shoot to produce floral buds instead of leaves and lateral buds.