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
Microscope slide of lily flower bud c.s.: 3 sepals, 3 petals, 6 stamens, 1 ovary
Angiosperm Life Cycle
© Kwantlen.ca/Horticulture
300 um
600 um
100 um
80 um
Anther chamber close-up in early stages of development showing diploid (2n) microsporocytes which undergo meiosis to form four genetically distinct haploid nuclei (1n)
Angiosperm Life Cycle
© Kwantlen.ca/Horticulture
Mature pollen from the lily: exine and one aperture (monocot)
Angiosperm Life Cycle
© Kwantlen.ca/Horticulture
10 um
500 um
Style (longitudinal section) with germinating pollen grains on the stigma
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
2
3
4
5
6
7
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
Embryo sac development in Clematis (typical of most dicots)
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