Plant Reproduction

1
Plant Reproduction

• Starr/Taggarts
• Biology
• The Unity and Diversity of Life, 9e
• Chapter 31

2
Key Concepts

• Sexual reproduction is the primary mode of
  reproduction of flowering plants
• Sexual reproduction of flowering plants involves
  the formation of spores and gametes which develop
  inside flowers
• Animals, air currents, and other agents transfer
  pollen grains to the female reproductive parts

3
Key Concepts

• Egg-producing female gametophytes develop in
  ovules
• After sperm fertilize eggs, seeds develop which
  consist of an embryo and tissues for nutrition
• While seeds develop, tissues of the ovary mature
  into fruits

4
Reproductive Structures of Flowering Plants

• Sporophyte
• Growth
• Mitotic division of a fertilized egg
• Flowers
• Gametophytes
• Sperm
• Eggs

5
Components of Flowers

• Growth at shoots from primary plant body
• Sepals (calyx)
• Petals (corolla)
• Enclose reproductive parts

6
(see previous slide)
an ovule
ovary wall
cell
seedling (2n)
integument
stalk
seed coat
seed
embryo (2n)
endosperm (3n)
ovary (cutaway view)
Diploid Stage Haploid Stage
Double Fertilization
Meiosis
pollen tube
embryo sac inside ovule
endosperm mother cell (n n)
(see previous slide)
integuments
egg (n)
Fig. 31.6b, p. 535
7
Where Pollen and Eggs Develop

• Stamen
• Filament
• Anther
• Carpel
• Stigma
• Style
• Ovary

• Perfect flower
• Male female parts
• Imperfect flower
• Male or female parts

8
Click to view animation.
animation
9
A New Generation Begins

• Cells in pollen sacs undergo meiosis to form
  microspores
• Mitosis forms male gametophyte (pollen grains)

• Cells in ovule undergo meiosis to form megaspores
• Mitosis without cytoplasmic division forms female
  gametophyte

10
The Female Gametophyte

• 7-celled embryo sac
• Six cells have single nucleus (n)
• One of these is the egg
• One cell has two nuclei (2n)
• Endosperm mother cell
• Will help form endosperm

11
Pollination to Fertilization

• Pollination
• Pollen grains to stigma
• Pollen tube grows to and penetrates embryo sac,
  releases two sperm
• Double fertilization
• One sperm fuses with egg nucleus
• One sperm fuses with nuclei of endosperm mother
  cell

12
From Zygote to Seeds and Fruits

• Fruit
• Mature ovary
• Cotyledons
• Seed leaves
• Dicots
• Monocots
• Seed
• Embryo, food reserves and coat

• Fleshy fruit
• Pericarp
• Endocarp
• Around seed
• Mesocarp
• Fleshy
• Exocarp
• Skin

13
nucleus
vacuole
Fig. 31.7a-d, p. 536
14
seed coat
A fruit (mature ovary) cut open to show seeds
(mature ovules).
cotyledon
embryos shoot tip
cotyledon
mature embryo within ovule
EMBRYO SPOROPHYTE
endosperm
embryos root tip
Fig. 31.7e -g, p. 536
15
fleshy fruit (from ovary tissues)
seed
Fig. 31.8a, b, p. 537
one of many individual fruits
16
Dispersal of Fruits and Seeds

• Air currents
• Animals
• Birds, mammals and insects
• Water
• Waxy coats
• Sacs of air for floating

17
Fig. 31.1, p. 530
18
Fig. 31.2, p. 531
How we see it
How bees see it
19
Asexual Reproduction of Flowering Plants

• Vegetative growth
• Mitosis
• Clone
• Parthenogenesis
• Embryo develops from unfertilized egg
• Induced propagation
• New plant from lead or tissue
• Shoot tips
• Vegetative
• Tissue culture

20
Fig. 31.12, p. 541
21
In Conclusion

• Sexual reproduction is the primary mode of a
  flowering plant cycle
• Gametophytes form in male and female floral parts
• Asexual reproduction can occur naturally or
  artificially by cuttings and graftings
• Most of the reproductive structures are attached
  to a receptacle

22
In Conclusion

• Anthers of stamens contain pollen sacs
• A carpel has an ovary where eggs develop
• Inside carpels, ovules form consisting of a
  female gametophyte and other supporting tissues
• At maturity, each ovule is a seed and integuments
  form the seed coat
• The ovary and other tissues mature into a fruit

23
In Conclusion

• Female gametophytes form as a result of meiosis
• The megaspore formed has multiple nuclei
• The female gametophyte results after cytoplasmic
  division which results in an egg, mother cell,
  and the endosperm
• Pollination refers to pollen grains arriving on a
  stigma

24
In Conclusion

• Germination involves a pollen tube growing
  through the tissues of the ovary
• Double fertilization results in endosperm
  formation and seeds and fruits maturing
• Fruits function to protect and disperse seeds
• Asexual vegetative growth and vegetative
  propagation allow asexual reproduction of a plant
• developed by M. Roig