Angiosperm Reproduction and Biotechnology

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Hazel carpellate flower

(carpels / female sex organs only)

Adapted for wind pollination

Slide 15

Pollination by Bees

Common dandelion under

normal light

Common dandelion under

ultraviolet light

Color = visual cue / signal to attract pollinators

Slide 16

Pollination by Flies

Blowfly on carrion flower

Fly egg

Chemical signal: Odor attracts flies

Slide 17

Nectar = chemical attractant

Hummingbird drinking nectar of poro flower

Pollination by Birds

Slide 18

Double Fertilization

After landing on a receptive stigma, a pollen grain produces a pollen tube that extends between the cells of the style toward the ovary.

Double fertilization results from the discharge of two sperm from the pollen tube into the embryo sac in the ovule.

Sperm + egg = zygote 2n

Sperm + two polar nuclei = endosperm 3n

One sperm fertilizes the egg, and the other combines with the polar nuclei, giving rise to the triploid (3n) food-storing endosperm.

Slide 19

Stigma

Pollen tube

2 sperm

Style

Ovary

Ovule

Micropyle

Ovule

Polar nuclei

Egg

Synergid

2 sperm

Endosperm

nucleus (3n)

(2 polar nuclei

plus sperm)

Zygote (2n)

(egg plus sperm)

Egg

Pollen grain

Polar nuclei

Growth of the pollen tube

and

double fertilization

Slide 20

Growth of the Pollen Tube

Stigma

Pollen tube

2 sperm

Style

Ovary

Ovule

Micropyle

Egg

Pollen grain

Polar nuclei

Slide 21

Embryo Sac in the Ovule

Ovule

Polar nuclei

Egg

Synergid

2 sperm

Slide 22

Double Fertilization:

Endosperm

nucleus (3n)

(2 polar nuclei

plus sperm)

Zygote (2n)

(egg plus sperm)

Slide 23

Seed Development, Form, and Function

After double fertilization, each ovule develops into a seed.

The ovary develops into a fruit enclosing the seed(s).

Slide 24

Endosperm Development

Endosperm development usually precedes embryo development.