Flower Structure and Function

• Leaf-like structures at the base of the flower are called sepals.

• They enclose the flower before it opens.

• They are usually green.

Inside the sepals are leaf-like blades called petals.

• They are often white or brightly colored.

• They surround and protect the reproductive parts.

• They attract insects to the flower.

A stamen is the male reproductive part of the flower.

• Each stamen has a long thin stalk called a filament.

• The filament supports the anther.

• The anther is a sac at the end of the stamen that produces pollen.

A pistil is the female reproductive part of a flower.

• The enlarged base is called an ovary.

• The ovary contains ovules that produce eggs.

• The slender stalk of the pistil is called a style.

• The style supports the stigma, the sticky end of the pistil that collects pollen.

Not all flowers have all of these parts.

Grass flowers do not have sepals or petals.

Corn plants produce both flowers that contain only male or female reproductive parts on the

same plant.

Some plants such as the Osage Orange tree have separate male and female plants

Pollination

• Before a flowering plant can reproduce, pollination must occur.

• Pollination occurs when pollen from the male structure or anther is transferred to the female structure or stigma.

Pollen may be transferred in different ways.

• Some pollen is transferred by the wind.

• Most pollen is transferred by insects.

Birds, bats, bees beetles, butterflies, and moths are important pollinators.

• Pollen from the anther sticks to the insect’s body.

• When the insect goes to the next flower, some of the pollen brushes off its body and sticks to the stigma.

Fertilization

• After a pollen grain reaches the stigma of a flower, chemicals on the stigma cause the pollen grain to form a tube through the stigma.

Fertilization

• The tube grows down towards the ovary to an ovule.

• Sperm produced by the pollen grain then travels through the pollen tube in the ovule.

Fertilization

• A sperm fertilizes an egg in the ovule.

• The ovary enlarges and becomes a fruit.

Fertilization

• The ovule develops into a seed.

Asexual reproduction in plants

• As only one parent is involved in asexual reproduction, all the offspring have exactly the same genes as their parent.

• The offspring are identical.

• Because of this, any genetic problems there may be will always be passed on to the new generation.

Stems

• In some species, stems arch over and take root at their tips, forming new plants.

• Wild strawberries do this.

Roots

• Some plants use their roots for asexual reproduction.

• The dandelion is a common example.

• They send up new stems from their roots.

Leaves

• Some plants can produce tiny plantlets that fall off and can take up an independent existence.

• Bryophyllum (Kalanchoë) is an example.