Section 22.2

KEY CONCEPT

Reproduction of flowering plants takes place within

flowers.

Flowers contain reproductive organs protected by

specialized leaves.

1. Sepals are outermost layer that protects developing flower

sepal

2. Petals can help to attract animal pollinators

petal

Flowers contain reproductive organs protected by

specialized leaves.

3. A stamen is the male structure of the flower.

4. filament supports the anther

5. anther produces pollen grains

stamen

filament anther

Flowers contain reproductive organs protected by

specialized leaves.

carpel style

stigma

ovary

6. The innermost layer of a flower is the female carpel.

7. stigma is sticky tip

8. style is tube leading from stigma to ovary

9. ovary produces female gametophyte

Flowers contain reproductive organs protected by

specialized leaves.

Flowering plants can be pollinated by wind or animals.

• Flowering plants pollinated when pollen grains land on

stigma.

• Wind pollinated flowers have

small flowers and large

amounts of pollen.

pollen grains landing on stigma

• Animal pollinated flowers have larger flowers and less

pollen.

pollen grains

– many flowering plants pollinated by animal pollinators

– pollination occurs as animal feeds from flower to flower

– animal pollination more efficient than wind pollination

Flowering plants can be pollinated by wind or animals.

Fertilization takes place within the flower.

• Male gametophytes, or pollen grains, are produced in the

anthers.

– male spore divides by mitosis to produce a pollen grain

of two haploid cells

– a thick wall surrounds the cells

pollen grain

2 haploid cells

thick coat

– female spore divides by mitosis 3 times, resulting in 8

nuclei

– membranes grow between them forming the 7-celled

female gametophyte

• One female gametophyte can form in each ovule of a

flower’s ovary.

Fertilization takes place within the flower.

• Pollination occurs when a pollen grain lands on a stigma.

pollen tube

sperm

stigma

– one cell from pollen grain forms pollen tube

– other cell forms two sperm that travel down tube

Pollination

endosperm

seed coat

embryo

– one sperm fertilizes

the egg

– other sperm unites

with polar nuclei,

forming endosperm

– endosperm provides

food supply for

embryo

• Flowering plants go through the process of double

fertilization.

Double Fertilization

• Each ovule becomes a seed.

• The surrounding ovary grows into a fruit.

Seeds and Fruit