Chapters 38 and 39

1
Chapters 38 and 39

• Plant Reproduction and Responses

2
Alternation of Generations

• Haploid and diploid generations take turns
  producing each other
• Diploid sporophyte (produces haploid spores by
  meiosis, spores divide mitotically and give rise
  to multicellular male and female haploid plants)
• Haploid gametophyte (by mitosis and cellular
  differentiation, these develop and produce
  gametes fertilization results in diploid
  zygotes, which divide by mitosis and form new
  sporophytes)

3
Flowers are specialized shoots bearing
reproductive organs of the angiosperm sporophyte

• Flowers are the reproductive shoots of the
  angiosperm sporophyte
• Typical 4 whorls of highly modified leaves
  separated by very short internodes
• Flowers are DETERMINATE SHOOTS stop growing once
  the flower and fruit are formed

4
Floral organs

• From outside in
• sepals
• petals
• stamens male reproductive organs
• -made up of anther and filament
• carpels female reproductive organs
• -made up of ovary, style, stigma
• Site of attachment on the stem receptacle

5
Stamen and carpels contain sporangia

• Male gametophytes are the pollen grains
• Female gametophytes are embryo sacs

6
Figure 38.1 Simplified overview of angiosperm
life cycle
7
Complete vs. incomplete flowersBisexual vs.
unisexual flowers

• Complete have all 4 floral organs present
• Incomplete lack one or more of the 4 floral
  organs
• ex. Grass blooms have no petals
• Bisexual has stamens and carpels
• Unisexual missing either stamens or carpels
• Plants that have unisexual flowers can either
  be monoecious or dioecious if staminate and
  carpellate flowers are on same plant, then are
  mono if on separate plants, then dioecious

8
 The Structure of a Flower
Section 24-1
9
Figure 38.4 The development of angiosperm
gametophytes (pollen and embryo sacs)
10
Self fertilization is usually avoidedpages
788-789

• Mechanisms to prevent
• dioecious plants
• different maturation rates on
• monoecious species
• structural arrangement
• self-incompatibility (S-genes)
• sporophytic self-incompatability

11
Figure 38.6 Pin and thrum flower types
reduce self-fertilization
12
Figure 38.7 Genetic basis of self-incompatibility
13
Figure 38.8 A possible mechanism of sporophytic
self-incompatibility (Layer 3)
14
Double fertilization

• Pollen grain absorbs moisture and germinates once
  on a receptive stigma
• (by germinates, mean grows a pollen tube that
  entends down between the cells of the style
  toward the ovary)
• The generative cell divides by mitosis and forms
  two sperm
• (germinated pollen grain is the mature male
  gametophyte)

15
Figure 38.9 Growth of the pollen tube and double
fertilization
16
Figure 244 The Life Cycle of a Gymnosperm
Section 24-1
Haploid (N) Diploid (2N)
MEIOSIS
FERTILIZATION
17
The Life Cycle of an Angiosperm
Section 24-1
Haploid (N) Diploid (2N)
MEIOSIS
Ovule
FERTILIZATION
18
Figure 38.10 The development of a dicot plant
embryo
19
Figure 38.11 Seed structure
Pages 791-792
Terms to know Seed coat Hypocotyl Radicle Epicoty
l Scutellem Coleorhiza Coleoptile
20
Figure 38.13 Mobilization of nutrients during
the germination of a barley seed
Page 793
21
Concept Map
Section 24-2
SeedGermination
in
have
have
that
that
22
Figure 38.14 Seed germination
23
Asexual reproduction

• Vegetative reproduction
• Fragmentation (see next slide)
• Apomixis produce seeds without flowers being
  fertilized

24
Compare/Contrast Table
Section 24-1
Comparing Plant Propagation Methods
Method Procedure
Cuttings
Grafting
Budding
25
Plant responses

• -Signal transduction
• -Hormones (see page 808)
• -Light -- Phototropisms
• -Gravitropisms
• -Thigmomorphogenesis
• -Stress

26
Figure 39.2 Review of a general model for
signal-transduction pathways
27
Figure 39.3 An example of signal transduction in
plants the role of phytochrome in the greening
response (Layer 1)
28
Figure 39.3 An example of signal transduction in
plants the role of phytochrome in the greening
response (Layer 2)
29
Figure 39.3 An example of signal transduction in
plants the role of phytochrome in the greening
response (Layer 3)
30
Hormones

• Auxin cell elongation (primary growth and
  secondary)
• Cytokinins cell division, differentiation,
  apical dominance
• Gibberellins stem elongation, fruit growth
• Abscisic acid slows down growth, seed dormancy,
  drought stress
• Ethylene fruit ripening, leaf abscission,
• Brassinosteroids inhibits root growth, slows
  down leaf abscission, promotes differentiation of
  xylem

31
Table 39.1 An Overview of Plant Hormones
32
Figure 39.4 Early experiments of phototropism
33
Figure 39.22 Photoperiodic control of flowering
34
Figure 39.23 Reversible effects of red and
far-red light on photoperiodic response
35
Figure 39.25 The statolith hypothesis for root
gravitropism
36
Figure 39.26 Altering gene expression by touch
in Arabidopsis
37
Figure 39.27 Rapid turgor movements by the
sensitive plant (Mimosa pudica)