1. Plant Reproduction
Chapter 30

2. The Plant Kingdom Nearly all are multicellular Eukaryotic Terrestrial
Vast majority are photoautotrophs
Energy from sun
Carbon dioxide from air
Minerals dissolved in water

3. Plant Kingdom Adaptations to land Well developed tissue Cuticle
Stomata
Protection of embryo
Alternations of generations
Sporophyte
Diploid
Produces spores by meiosis
Reproductive structure

4. Plant Kingdom Gametophyte Haploid Produces gametes Egg and sperm
Formed by mitosis
Egg and sperm fuse to form zygote
Undergoes mitosis
Forms sporophyte

5. Evolutionary Trend multicelled sporophyte (2n) mitosis zygote (2n)
Diploid
Haploid
fertilization
meiosis
gametes
(2n)
spores
(2n)
multicelled
gametophytes
(n)
mitosis
mitosis

6. zygote only, no sporophyte
sporophyte’s importance
gametophyte’s importance
green algae
bryophytes
ferns
gymnosperms
angiosperms

7. Imperiled Sexual Partners
Impacts, Issues Video
Imperiled Sexual Partners

8. Plants and Pollinators
Pollination
Transfer of pollen to the stigma
Pollen had evolved by 390 million years ago
Sperm packed inside a nutritious package
Transferred first by wind currents (abiotic)
Later transferred by insects
Plants that attracted insect pollinators with flowers had a reproductive advantage

9. Pollinators Pollination vectors Winds Insects Birds Other animals
Coevolution with pollinators

10. Hummingbird drinking nectar of columbine flower
Figure 30.6bb Exploring flower pollination (part 2b: hummingbird)
Hummingbird drinking nectar of columbine flower 10

11. Long-nosed bat feeding on cactus
Figure 30.6ba Exploring flower pollination (part 2a: long-nosed bat)
Long-nosed bat feeding on cactus
flower at night 11

12. Pollinators Visual cues Size, shape, color, pattern Olfactory cues
Odors from fruit or flowers
Pollinators follow concentration gradient of volatile chemicals to their sources
Reinforcements
Nectar

13. Bee-attracting flower pattern
Pollen Formation
Bee-attracting flower pattern

14. Common dandelion Common dandelion under ultraviolet under normal light
Figure 30.6ac Exploring flower pollination (part 1c: dandelion)
Common dandelion
under ultraviolet
light
Common dandelion
under normal light 14

15. Angiosperm Life Cycle Diploid sporophytes (2n)
produce spores (n) by meiosis
these grow into haploid gametophytes (n)
Gametophytes (n)
produce haploid gametes (n) by mitosis
fertilization of gametes produces a sporophyte 15

16. DIPLOID HAPLOID fertilization
mature sporophyte
seed
meiosis (within anther)
meiosis (within ovary)
DIPLOID
HAPLOID
fertilization
gametes (sperm)
microspores
(mitosis)
male gametophyte
gametes (eggs)
megaspores
(mitosis)
female gametophyte

17. Angiosperm Life Cycle
In angiosperms, the sporophyte is the dominant generation, the large plant that we see
The gametophytes are reduced in size and depend on the sporophyte for nutrients
The angiosperm life cycle is characterized by “three Fs”:
Flowers
Double Fertilization
Fruits
For the Discovery Video Plant Pollination, go to Animation and Video Files. 17

18. Flower Structure and Function
Flowers are the reproductive shoots of the angiosperm sporophyte
they attach to a part of the stem called the receptacle 18

19. Flower Structure Nonfertile parts Sepals Receptacle Fertile parts
STAMEN
(male reproductive part)
CARPEL
(female reproductive part)
filament
anther
stigma
style
ovary
Nonfertile parts
Sepals
Receptacle
Fertile parts
Male stamens
Female carpel (ovary)
OVULE (forms within ovary)
petal (all petals combined are the flower’s corolla)
sepal (all sepals combined are the flower’s calyx)
receptacle

20. Pollen Formation
Microspores to pollen

21. Development of Male Gametophytes in Pollen Grains
Microspore Mother Cell (2n)
Goes through meiosis to produce microscpores (n)
Microspores (n)
give rise to pollen
takes place in the microsporangia, or pollen sacs, of anthers
each microspore undergoes mitosis to produce two cells
the generative cell
2 sperm
the tube cell
pollen tube 21

22. Pollen Formation pollen sac anther filament microspore mother cell
Diploid Stage
Haploid Stage
Meiosis
microspores
pollen grain
pollen tube
stigma
sperm nuclei
mature male gametophyte
style of carpel

23. Egg Formation
Megaspores to eggs

24. Egg Formation Meiosis in ovule produces megaspores
All megaspores but one disintegrate
It undergoes mitosis three times without cytoplasmic division
Result is a cell with eight nuclei
Cytoplasmic division produces seven-celled female gametophyte
6 cells with 1 nucleus
1 being the egg
1 cell with 2 nuclei
Dikaryotic
Forms the endosperm

25. Pollination / Double Fertilization
transfer of pollen grains to a receptive stigma
Germination
pollen tube begins to grow
delivers the sperm
1 to fertilize the egg (2n)
1 to the polar nuclei
gives rise to the triploid endosperm (3n)
nutritive tissue of the seed

26. Pollen Stigma grain Pollen tube Two sperm Tube nucleus Style Ovary
Polar
nuclei
Ovule
Figure Growth of the pollen tube and double fertilization (step 1)
Egg
Micropyle 26

27. Pollen Stigma grain Pollen tube Ovule Two sperm Tube Polar nuclei
nucleus
Polar
nuclei
Style
Egg
Ovary
Synergid
Polar
nuclei
Ovule
Figure Growth of the pollen tube and double fertilization (step 2)
Two sperm
Egg
Micropyle 27

28. Pollen grain Stigma Endosperm nucleus (3n) (two polar nuclei
plus sperm)
Pollen tube
Ovule
Two sperm
Tube
nucleus
Polar
nuclei
Style
Egg
Ovary
Synergid
Polar
nuclei
Zygote (2n)
(egg plus
sperm)
Ovule
Figure Growth of the pollen tube and double fertilization (step 3)
Two sperm
Egg
Micropyle 28

29. Seed Formation Seed A mature ovule encases an embryo sporophyte
food reserves inside a protective coat
enters a state of dormancy
wherein it stops growing and slows metabolism
mature seed is only about 5–15% water 29

30. Nourishing the Embryo Dicot embryo Absorbs nutrients from endosperm
Stores them in its two cotyledons
Monocot embryo
Digestive enzymes are stockpiled in the single cotyledon
Enzymes do not tap into the endosperm until the seed germinates

31. Eudicot seed development
Nourishing the Embryo
Eudicot seed development

32. Seed Dormancy: An Adaptation for Tough Times
increases the chances that germination will occur at a time and place most advantageous to the seedling
Breaking of seed dormancy often requires environmental cues
such as temperature or lighting changes 32

33. Seed Germination / Seedling Development
Germination depends on imbibition,
the uptake of water due to low water potential of the dry seed
The radicle (embryonic root) emerges first
Next, the shoot tip breaks through the soil surface 33

34. Fruit A fruit develops from the ovary
It protects the enclosed seeds and aids in seed dispersal

35. (a) Simple fruit (b) Aggregate fruit (c) Multiple fruit
Stigma
Style
Carpels
Stamen
Flower
Petal
Ovary
Stamen
Stamen
Sepal
Stigma
Ovary (in
receptacle)
Ovule
Ovule
Pea flower
Raspberry flower
Pineapple inflorescence
Apple flower
Each segment
develops
from the
carpel
of one
flower
Remains of
stamens and styles
Carpel
(fruitlet)
Stigma
Sepals
Seed
Ovary
Stamen
Figure Developmental origins of fruits
Seed
Receptacle
Pea fruit
Raspberry fruit
Pineapple fruit
Apple fruit
(a) Simple fruit
(b) Aggregate fruit
(c) Multiple fruit
(d) Accessory fruit 35

36. Seed Dispersal Fruit structure is adapted to mode of dispersal
Some modes of seed dispersal:
Wind currents
Water currents
Animals

37. wing
seed (in carpel)

38. Dandelion “seeds” (actually one-seeded fruits)
Dandelion fruit
Figure 30.12ac Exploring fruit and seed dispersal (part 1c: dandelion)
Dandelion “seeds” (actually one-seeded fruits) 38

40. Ant carrying seed with attached “food body”
Figure 30.12bd Exploring fruit and seed dispersal (part 2d: food bodies)
Ant carrying seed with
attached “food body” 40

41. Advantages and Disadvantages of Asexual vs Sexual Reproduction
Asexual reproduction is also called vegetative reproduction
beneficial to a successful plant in a stable environment
a clone of plants is vulnerable to local extinction if there is an environmental change
Sexual reproduction
generates genetic variation that makes evolutionary adaptation possible 41