Angiosperm Reproduction

Chapter 19

Major Evolutionary Advances

Flowers - 140 mya

5,000mya

4,000mya

3,000mya

2,000mya

1,000mya

EarthForms

ProkaryoticCells

EukaryoticCells

MulticellularPlants

Vascular

tissue

Seeds

Flowers

Life - 3,800 myaProkaryotic cell/autotrophic

Eukaryotic cell - 1,400 myaMulticellar plants - 1,000 myaVascular tissue - 430 mya

Needed on land - why?Seeds - 350 mya

Place on the time scale, the following events:

1. Earth2. Prokaryotes3. Eukaryotes4. Multicellular life5. Vascular tissue6. Seeds7. Flowers

Flower variation

Complete• has all 4 whorls

Incomplete• lacks one or more

of whorls (sepals, petals, stamens or carpels)

Flower variationPerfect

• both androecium and gynoecium

Imperfect• carpellate or

staminate flower only• if both carpellate and

staminate flowers are on same plant called monoecious

• if on different plants called dioecious

Fertilization

• Pollination: transfer of pollen grains from anther to pistil

• Pollen grain onto stigma• Germination - tube cell

produces pollen tube, generative cell divides to form 2 sperm cells

• Double Fertilization:• 2 sperm enter

embryo sac: • 1 sperm fertilizes egg to form zygote• other sperm fertilizes polar nuclei to

form endosperm

Sexual Reproduction

Four events must occur for successful reproduction in angiosperms:

1. Pollination2. Pollen grain growth to ovule3. Successful fertilization4. Successful seed development

Sexual Reproduction

• Inbreeding• Result of self-pollination & self-fertilization• Results in inbreeding depression

• Outcrossing• Result of cross-pollination & cross-fertilization• Results in hybrid vigor

• What process is “best”? Why?• How do plants promote this?

Sexual Reproduction• Unisexual flowers• Monoecious plants

• Dioecious plants

Sexual ReproductionBisexual flowers

• Protandry - stamens mature before stigma

Hibiscus

MagnoliaEpilobium (fireweed)

Protandry

• Protogyny - stigma matures before stamens

• Heterostyly - physical separation between stigma and stamen

Sexual ReproductionBisexual flowers

Self-incompatibility• Pollen grain-

stigma surface: no germination• Pollen tube

growth: tube “dies”• Fertilization:

inviable zygotes

Amarylis

Pollination• Define:• transfer of pollen to stigma

• How is self-fertilization prevented (or reduced) through pollination mechanisms?• unisexual flowers (monoecious plants)• unisexual flowers (dioecious plants)• protandry• protogyny• heterostyly

Fertilization:

ovule

• Define:• combining of sperm + egg AND sperm +

polar nuclei = double fertilization

Fertilization

megagametophyte(female gametophyte)

microgametophyte(male gametophyte)

ovule

Fertilization

Fertilization

• What occurs after double fertilization?• embryo development

• next generation• endosperm development

• nourishment for embryo• What structure is

formed?• seed

• embryo• endosperm• seed coat

• Where is the seed housed?• inside ovary• matures into a fruit

• ovary wall = pericarp

Seed germination & growth

How might reproductive success be measured in an angiosperm?

Funk, Lisa. 1997. A comparison of reproduction in self and outcrossed purple poppy mallow flowers (Callirhoe involucrata). Results presented at the 1997 Nebraska Academy of Sciences Annual Meeting.

Gyno-dioecious species

Hermaphroditc flowers on some plantsMale-sterile flowers on other plants

Funk, Lisa. 1997. A comparison of reproduction in self and outcrossed purple poppy mallow flowers (Callirhoe involucrata). Results presented at the 1997 Nebraska Academy of Sciences Annual Meeting.

4 Treatments• Selfed• Outcrossed • Pollinator excluded• Control

Fruit set measured

What conclusions can be drawn?

• What conclusions can be drawn?• What is the role of gyno-dioecy in

plant reproduction and reproductive success in Callirhoe involucrata?

Funk, Lisa. 1997. A comparison of reproduction in self and outcrossed purple poppy mallow flowers (Callirhoe involucrata). Results presented at the 1997 Nebraska Academy of Sciences Annual Meeting.