1. Chapter 24
Reproduction
in Plants
Lecture Outline
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2.  Alternation of generations
 Sporophyte
 Dominant in flowering plants
 Bears flowers – reproductive structure
 Diploid or 2n
 Produces haploid microspores and megaspores by meiosis
 Gametophyte
 Haploid or 1n
 Produces gametes
 Microspore undergoes mitosis and become a pollen grain, a male
gametophyte
 Megaspore undergoes mitosis to become embryo sac, a female
gametophyte
 Upon fertilization, the cycle returns to the 2n sporophyte
24-2

3.  Plant Reproduction, cont.
 Once a sperm fertilizes an egg, the zygote becomes an embryo,
still within an ovule
 Ovule develops into a seed, which contains the embryo and
stored food surrounded by a seed coat
 Ovary becomes a fruit, which aids in dispersing the seeds
 When a seed germinates, a new sporophyte emerges and,
through mitosis and growth, becomes a mature organism
 Sexual life cycle of flowering plants is adapted to land
24-3

4. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 24.1A
Alternation of
8 generations in
flowering plants
mi
to
s is
anther
7 1 sporophyte
seed
2
diploid (2n) ovule
zygote 6 ovary
FERTILIZATION MEIOSIS
haploid (n)
3 microspore
egg megaspore
sperm m 4
5 ito
si
s
Male gametophyte
(pollen grain)
Female gametophyte 24-4
(embryo sac)

5.  Flowers are unique to angiosperms
 Produce spores, protect gametophyte, attract
pollinator, produce fruits
 Exs. of pollinators: birds, beetles, flies, butterflies,
bats
 Typical flower
 4 whorls of modified leaves attached to a receptacle
1. Sepals – protect bud
2. Petals – attract pollinators
3. Stamens – Male Portion (anther & filament)
4. Carpel – Female Portion (stigma, style & ovary)
24-5

6. Figure 24.1B Anatomy of a flower
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
stamen carpel
anther stigma
filament style
ovary
petal ovule
sepal receptacle
24-6

7. Figure 24.1C b. Azaleas are eudicots
Eudicots have flower parts in fours or fives (p = petal; s = sepal)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
p3
p2
carpel
stamen
p4
petal p1
p5
b.
a: © Farley Bridges; b: © Pat Pendarvis
24-7

8. Figure 24.1D A corn plant is monoecious (flowers that are only male or only female
a. The staminate flowers produce pollen that is carried by wind to
b. the carpellate flowers, where ears of corn develop. 24-8

9. Figure 24B
Butterflies, birds, and bats are adapted for acquiring nectar from certain flowers.
Flowers that attract beetles produce much pollen and those that attract flies have
24-9
the smell of rotting flesh

10.  Sexual reproduction involves
1. Production of pollen grains (male gametophytes) in
the anthers of stamens
2. Production of an embryo sac (female gametophyte)
in an ovule located within the ovary of a carpel
 Pollination
 Pollen transferred from anther to stigma so an egg
within female gametophyte is fertilized
 Most angiosperms use animals to carry out
pollination
24-10

11. Figure 24.2A Life cycle of flowering plants
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Stamen Carpel
anther stigma
filament style
ovary
ovule
Mitosis
Sporophyte
stigma
Carpel
fruit
(mature ovary) style
seed Anther
(mature ovule)
ovary
seedcoat Ovule
pollen sac
embryo
endosperm (3n) microspore megaspore
Seed mother cell mothe rcell
diploid (2n)
MEIOSIS MEIOSIS
24-11

12. Figure 24.2A Life cycle of flowering plants (cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
MEIOSIS
haploid (n)
Pollen grain Microspores
Mi
tos
(all survive)
is
Megaspores
sperm and pollen POLLINATION (one survives)
polar nuclei tube
fuse sperm generative cell
sperm and (mature male
egg fuse gametophyte) degenerating
egg megaspores
DOUBLE FERTILIZATION
Mi
Ovule
tos
is
Embryosac
(mature female gametophyte)
24-12

13. Figure 24.2B Wind pollination of a grass, with SEM of pollen grains
24-13

14. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
nectar guides
As we see it As a bee sees it
(both): © Heather Angel/Natural Visions
 Coevolution
 As one species changes, the other changes too, so
that in the end, the two species are suited to one
another 24-14

15.  Double fertilization is unique in angiosperms
 Results in not only a zygote but also a food source for
the developing zygote
 Endosperm – nutritive tissue developing embryonic
sporophyte uses as energy source
 Mature seed contains
 Embryo – will develop into the plant
 Stored food – endosperm
 Seed coat – develops from ovule wall for protection
24-15

16. Figure 24.2D The parts of a bean seed, a eudicot
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Seed coat
immature
leaves Embryo
hypocotyl
radicle
Cotyledon
(stored food)
(right): © Dwight Kuhn
24-16

17. 24.4 The ovary becomes a fruit, which
assists in sporophyte dispersal
 Fruit = a ripened ovary
 Protects and helps disperse the plant
(“marketing for the seeds”)
24-17

18. 24.4 The ovary becomes a fruit, which
assists in sporophyte dispersal
 Fleshy Versus Dry Fruits
 Dry fruits
 Exs: peas, maples
 Fleshy fruits
 Exs: apples, strawberries, tomatoes, corn
24-18

19. Figure 24.4 Fruit diversity
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
pea flower pea pod
pericarp
stigma (fruit wall)
ovary wall seed
ovule
1 Pea pods are a dry, dehiscent
(can open to reveal seeds) fruit. 24-19

20. Figure 24.4 Fruit diversity (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
seed covered by pericarp
wing
2 Maple tree fruits are dry, in dehiscent.
© James Mauseth
24-20

21.  Simple Versus Aggregate & Multiple Fruits
 Simple fruits are derived from the simple ovary of a
single carpel Exs: grapes, tomatoes
 Accessory fruits form from other flower parts in
addition to ovary Exs: strawberry, apple
 Aggregate and multiple fruits are examples of
compound fruits derived from several individual
ovaries
 Strawberry – aggregate fruit, each ovary becomes a one-
seeded fruit called an achene
 Pineapple – a multiple fruit derived from many individual
flowers, each with its own carpel
24-21

22. Figure 24.4 Fruit diversity (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
one fruit
flesh is from
receptacle
3 Strawberries are a fleshy aggregate fruit.
© Corbis RF
24-22

23. Figure 24.4 Fruit diversity (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
one fruit
fruits from
ovaries of
one flower
4 Raspberries are an aggregate fruit.
© C Squared Studios/Getty RF
24-23

24. Figure 24.4
Fruit diversity (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
fruits from
ovaries of
many flowers
one fruit
5 Pineapple is a multiple fruit. 24-24
© BJ Miller/Biological Photo Service

25.  Germination – seeds form into a seedling
 Doesn’t usually take place until there is sufficient
water, warmth, and oxygen to sustain growth
 For seeds, dormancy is the time during which no
growth occurs, even though conditions may be
favorable for growth
24-25

26. Figure 24.5A Structure and germination of a common bean seed
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Embryo:
epicotyl-
plumule Cotyledon
(two)
hypocotyl
radicle
Seed coat
Cotyledon
(stored food)
Bean seed 24-26
(right): © Ed Reschke

27. Figure 24.5A Structure and germination of a common bean seed (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
first true leaves
(primary leaves) epicotyl
with red
cotyledons
seed cotyledons
coat (two) hypocotyl
hypocotyl
secondary
root
primary
primary
root
root
24-27

28. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Figure 24.5B
Structure and
pericarp
germination of a
Seed coat corn kernel
endosperm
cotyledon
(one)
coleoptile
Embryo:
plumule
radicle
coleorhiza
Corn kernel
true leaf
first leaf
coleoptile prop root
coleoptile
radicle
adventitious
root
primary root
coleorhiza
24-28
(Top right): © James Mauseth

29. 24.6 Plants have various ways of
reproducing asexually
 Also called vegetative reproduction
 Type of cloning – offspring exactly like parent
 Plants can grow from axillary buds of above or
below ground stems
 Rhizome – underground horizontal stem (iris, many
grasses)
 Tuber – enlarged portion of rhizome (potato)
 Corm – bulbous underground stems (onion)
24-29

30. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
stolon
Asexually produced offspring
© G.I. Bernard/Animals Animals
Figure 24.6 Asexual reproduction in plants 24-30

31. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Rhizome Tuber Corm
rhizome
branch papery
axillary
leaves
adventitious roots bud
corm
axillary
bud
rhizome
tuber
adventitious roots
Figure 24.6 Asexual reproduction in plants (cont.) 24-31

32. 24.7 Cloning of plants in tissue
culture assists agriculture
 Tissue culture
 Growth of a tissue in an artificial liquid or on agar
 3 methods
 Somatic embryogenesis – technique that uses hormones to
cause plant tissues to generate small masses of cells
 Meristem tissue culture – many new shoot tips from a single
shoot tip
 Anther tissue culture – produces haploid plantlets or
chromosomal doubling chemically induced
24-32

33. Figure 24.7A Somatic embryogenesis
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
a. Protoplasts, naked cells b. Cell wall regeneration
(both): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604
24-33

34. Figure 24.7A Somatic embryogenesis (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
c. Aggregates of cells d. Callus, undifferentiated mass
(both): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604
24-34

35. Figure 24.7A Somatic embryogenesis (Cont.)
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
e. Somatic embryo f. Plantlet
(both): Courtesy Prof. Dr. Hans-Ulrich Koop, from Plant Cell Reports, 17:601-604 24-35

36. Figure 24.7B Producing whole plants from meristem tissue
24-36

37. Connecting the Concepts:
Chapter 24
 Life, as we know it, would not be possible without
vascular plants
 Although we now live in an industrialized society, we are
still dependent on plants and have put them to many
more uses
 We grow plants for food, shelter, beauty and substances for
industry
 Half of all pharmaceutical drugs have their origin in plants
24-37