Flower parts of lily: 3 sepals, 3 petals, 6 anthers each with 4 pollen chambers, and ovary

with compound pistil (3 carpels)

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Microscope slide of lily flower bud c.s.: 3 sepals, 3 petals, 6 stamens, 1 ovary

Anther chamber close-up in early stages of development showing diploid (2n) micro-

sporocytes which undergo meiosis to form four genetically distinct haploid nuclei (1n)

100 um

300 um 600 um

80 um

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Mature pollen from the lily: exine and one aperture (monocot) Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Style (longitudinal section) with germinating pollen grains on the stigma

500 um

10 um

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Ovary and Ovule close-ups showing two stages of meiosis which will result in four

genetically distinct haploid nuclei. Three nuclei will degenerate. The remaining nuclei will

undergo mitosis (occurs three times) to form 8 haploid nuclei (genetially identical) in an

“embryo sac”

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

1. Megasporocyte (diploid)

2. Meiosis telephase I

3. Meiosis telephase II (four megaspores – all genetically distinct)

4. One functional megaspore (n) remains, three other degenerate

5. Megaspore divides by mitosis

6. Nuclei divide again by mitosis

7. Mitosis takes place once more resulting in 8 nuclei that move to different parts of the embryo

sac cell (and may later become cells themselves): the two central cell nuclei will be fertilized

by one sperm and fuse to form 3N endosperm nuclei (double fertilization); the egg cell will be

fertilized to become the zygote and later the embryo; the two synergids (on either side of egg)

will degenerate as will the three antipodals at the other end of the embryo sac

1

Embryo sac development in Clematis (typical of most dicots)

2 3

4 5 6

7

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Dicot flower model with simple pistil: ovary, ovule, pollen tube, embryo sac (double

fertilization: two central cell nuclei will be fertilized by one sperm and fuse to form 3N

endosperm nuclei, the egg cell will be fertilized to become the zygote and later the embryo;

the two synergids on either side of egg will degenerate as will the three antipodals at the

other end of the embryo sac)

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Dicot flower model with compound pistil: stigma, style, pollen tube, ovary, ovule

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Immature seed l.s. with embryo (arrow) surrounded by endosperm tissue (most angiosperm

plants form 3n endosperm)

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Seeds (mature ovules) inside mature capsules of lily. The seed coat derived from the

integuments. The capsule pericarp is the ripened ovary wall.

Angiosperm Life Cycle © Kwantlen.ca/Horticulture

Self test #1: What are the arrows pointing at?

Angiosperm Life Cycle © Kwantlen.ca/Horticulture