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Title: Biology%20of%20Propagation


1
Chapter 2
  • Biology of Propagation

2
Biology of Propagation
  • Genetics
  • Genotype
  • All characteristics controlled by genes
  • Phenotype
  • Overall appearance and performance
  • Includes size, vigor, color, shape, adaptations
  • Results from interaction of the genotype with the
    surrounding environment

3
Biology of Propagation
  • What is a propagule?
  • Any plant part used to produce a new plant(s)
  • Types
  • Seeds, cuttings, layers, buds, scions, bulbs,
    corms, tubers
  • In plant propagation, we multiply plants using
    propagules of a specific genotype

4
Biology of Propagation
  • Genetic control in propagation
  • Sporophytic stage vegetative growth through
    mitosis (roots and shoots)
  • Gametophytic stage reproductive structures
    (flowers) producing gametes (reproductive cells)
    through meiosis

5
Sporophytic stage
6
Mitosis
7
Interphase
Blood Lily
Early prophase
Late prophase
8
Metaphase
Anaphase
Telophase
Resumption of Interphase
9
Meristems
10
Meristems
11
Meristems
Vascular cambium
12
Sporophytic/Gametophytic stages
13
Sporophytic/Gametophytic stage
14
Meiosis (Mi-Oh-Sis)
15
Biology of Propagation
  • Mitosis
  • Asexual reproduction
  • Vegetative propagation
  • Results in a diploid of chromosomes (2n)
  • Example plants in the genus, Prunus, have
    multiples of 8 chromosomes (n)
  • Peach and apricot have vegetative cells with 16
    (2n)
  • Cherries have vegetative cells with 24 (3n)
  • Plums have vegetative cells with 32 (4n)

16
Biology of Propagation
  • How do plants grow?
  • Cell division (mitosis)
  • Cell enlargement
  • Cell differentiation

17
Biology of Propagation
  • Mitosis occurs in
  • Shoot tip
  • 1 increases length
  • Root tip

18
Biology of Propagation
  • Meristem
  • Any growing region, typically in the roots or
    shoot tips
  • Other instances of mitosis
  • Wound healing ( callus)
  • Why important to plant propagation?

19
Biology of Propagation
  • Mitosis is CLONING!
  • No change in genotype (genes)
  • Progeny are genetic copies of the original plant
  • Cuttings are a type of cloning!
  • Tissue culture is a type of cloning!
  • Mutation
  • Genetic changes
  • Spontaneous
  • Created due to environmental factors

20
Biology of Propagation
  • Totipotency
  • Each living cell has the potential (genetic
    information) to reproduce the entire organism
  • Important in tissue culture
  • Competency
  • Potential of a given cell or tissue to develop in
    a particular way (roots, buds, etc.)
  • Determinism
  • How committed the cell is to produce specific
    organs (flowers or leaves, etc.)

21
Biology of Propagation
  • Meiosis (sexual reproduction)
  • For seedling propagation
  • Gametophytic generation
  • Flowers with sperm (in pollen) and egg (ovule)
  • Each is haploid
  • Meiosis is the process of producing male
  • and female gametes

22
Biology of Propagation
  • Genotype of a seedling determines its
  • Morphological appearance
  • Physiological characteristics
  • Interaction with the environment
  • Survival of the fittest

23
Biology of Propagation
  • Variability in seedlings depends on
  • Transfer of genetic material from parents
  • Dominance/recessiveness of traits
  • Gregor Mendel 1860s
  • Charles Darwin (Origin of Species, 1859)
  • Plant breeders control genetic variability
  • Biotech is specialized type of breeding

24
Biology of Propagation
  • Genetic engineering and biotechnology
  • Combine different kinds of DNA by transformation
    using bacteria
  • Agrobacterium tumefaciens
  • Agrobacterium rhizogenes
  • Or by direct bombardment of cells
  • By microscopic gold pellets coated with DNA
  • Produces transgenic plants
  • Also called recombinant DNA technology

25
Crown gall caused by Agrobacterium tumefaciens
26
Gene gun
Transformed rice embryos
27
Biology of Propagation
  • Gene expression
  • Based on DNA (genes) to produce plant structures
    and growth patterns
  • Are often influenced by the environment

28
Biology of Propagation
  • Epigenetic
  • Differences in development not involving a change
    in DNA
  • Formation of specific structures
  • (stems, roots, leaves, flowers)
  • Developmental cycles
  • Seasonal (phenology) leaf coloration, leaf
    abscission
  • Life (ontogeny) phase changes from juvenile to
    adult
  • Induction of adventitious roots, shoots or embryos

29
Biology of Propagation
30
Biology of Propagation
  • Hormonal control of plant growth development
  • Hormone - a naturally occurring chemical in
    plants (endogenous) that regulates growth and
    development

31
Biology of Propagation
  • Auxins
  • Indoleacetic acid (IAA)
  • Made in developing leaves
  • Moves from top to bottom of plant
  • Causes coleoptile bending (light degrades)
  • Inhibits lateral (side) buds apical dominance
  • Induces roots (adventitious) on cuttings
  • Mode-of-action NOT REALLY KNOWN!
  • Synthetic auxins (1935)
  • IBA indolebutyric acid
  • NAA naphthalene acetic acid

32
IAA molecule
33
Basal movement of auxin in coleoptile
34
Basal movement of auxin in coleoptile
35
Location of light sensing in shoot tip
This experiment was conducted by Charles Darwin
in 1880
Aluminum cap No bending
Only shoot tip exposed
36
Location of light sensing in shoot tip
  • What Darwin stated
  • we must therefore conclude that some influence
    is transmitted from the tip to the more basal
    regions of the shoot thereby regulating growth
    and inducing curvature
  • influence was the first reference to hormonal
    regulation in plants
  • influence IAA

37
Effects of specific light wavelengths on auxin
38
Coleoptile - No Auxin Coleoptile Auxin
39
Stimulates adventitious rooting
40
Auxin actively transported to basal end of
shootsregardless of orientation
Bamboo shoots Upside-down
41
Bean with suppressed axillary buds
42
Bean with shoot tip removed
Axillary buds no longer suppressed!
43
Shoot tip removed and replaced with a capsule
containing lanolin IAA
Axillary buds suppressed!
44
Biology of Propagation
  • Cytokinins
  • Essential for cell division
  • Discovered by Dr. Skoog at Univ. of Wisconsin
  • 1944
  • Kinetin from autoclaved fish sperm isolated
  • Zeatin from corn
  • 2iP (isopentenladenine)
  • BA (benzyladenine)
  • Produced by Rhizobium and Agrobacterium

45
Zeatin molecule
46
Biology of Propagation
  • Ratios important
  • Mode-of-action of cytokinins also NOT KNOWN!

47
Stimulation of root production
48
Stimulation of shoot production
49
Callus formed from even balance
50
Biology of Propagation
  • Gibberellins
  • Japanese discovered prior to WWII (early 1940s)
  • Discovered on abnormally-tall rice plants
  • Caused by a fungus called, Gibberella
  • Most active compound is GA3
  • Found in seeds
  • Controls seed dormancy
  • Controls germination
  • Transported in xylem and phloem
  • Promotes shoot elongation via inc. cell division
    and elongation

51
Gibberellic Acid (GA3) molecule
52
Dwarf peas response to GA3
GA3 - GA3
53
Biology of Propagation
  • Abscisic Acid (ABA)
  • Naturally occurring
  • Growth inhibitor
  • Controls dormancy of buds and seeds
  • Controls leaf and fruit abscission
  • Important in moisture stress in plants
  • Regulates stomatal closure
  • Regulates water uptake by roots

54
Abscisic Acid Molecule
55
ABA effects on seed germination
ABA After ABA washed off
56
Biology of Propagation
  • Ethylene
  • A gas
  • Causes senescence in flowers
  • Causes flower, fruit and leaf abscission
  • Can induce flowering
  • Can induce adventitious roots
  • Can stimulate germination of some seeds
  • Is a response to wounding and stress
  • Causes ripening and fruit maturation
  • Ethephon thinning agent in apples, promotes
    ripening
  • Currently work being conducted on ways to block
    the action of this gas

57
Ethylene Gas Molecule
58
Ethylene important in ripening
59
Bromeliad
60
Pineapple (Anana cosmosus)
61
Biology of Propagation
  • Life cycles in plants
  • Ontogenetic changes in growth and development
  • patterns over the life of the plant
  • Examples
  • Annuals - complete entire life cycle in 1
    growing
  • season
  • Biennial - complete entire life cycle in 2
    growing
  • seasons. 1st year vegetative rosette, 2nd
    year
  • flowers and seeds
  • Perennial - plants that live more than 2 years
  • Herbaceous perennials (bulb, rhizome, crown,
  • stolon)
  • Woody perennials (woody stems above ground)

62
Biology of Propagation
  • Seedlings
  • Develops from a seed
  • Flowering a response to
  • Chilling (vernalization)
  • Photoperiod (daylength)

63
Biology of Propagation
  • Another type of ontogenetic aging is
  • Phase change (juvenile to adult) cyclophysis
  • Maturation when in the adult phase
  • Shift from vegetative to reproductive
  • Can affect rooting of cuttings
  • Juvenile cutting of ivy is easy to root
  • Adult cutting is difficult
  • Juvenile citrus and black locust have spines
  • Mature citrus and black locust lack spines

64
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65
Juvenile
Mature
66
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67
Stipular spines on juvenile black locust
68
Biology of Propagation
  • Clonal life cycle
  • Vegetative propagules retain their juvenile or
    mature characteristics depending on where on the
    plant they were taken from
  • Cone-of-Juvenility

69
Cone-of-Juvenility
70
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71
Biology of Propagation
  • Plant Nomenclature
  • Labeling is critical in plant propagation
  • Prunus persica L. peach
  • Species a population of plants recognized by
  • similar traits and which interbreed
  • Propagated by seed

72
Biology of Propagation
  • Cline - continuous variation due to environment
    along the range of a species
  • Ecotype - distinct and discontinuous variation
    due to environment

73
Cline for Acer rubrum (red maple)
74
Pseudotsuga menziesii (Douglas fir)
75
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77
Zone 4
Zone 6
78
Ecotypes of Pseudotsuga menziesii (Douglas fir)
79
Biology of Propagation
  • Interspecific hybrid- interbreeding between
    species (rare)
  • Prunus x cistena purple-leaf sand cherry
  • Parentage
  • (Prunus pumila x Prunus cerasifera)
  • This hybrid is sterile and many interspecific
  • crosses are!

80
Prunus pumila (female)
81
Prunus cerasifera (male)
82
Prunus x cistena (sterile hybrid)
83
Prunus x cistena (sterile hybrid)
84
Biology of Propagation
  • Intergeneric hybrid - interbreeding between
    genera (very rare)
  • X Cupressocyparis leylandii
  • Parentage
  • Cupressus macrocarpa x Chamaecyparis nootkatensis

85
  • Parentage
  • Cupressus macrocarpa

86
  • Parentage
  • Chamaecyparis nootkatensis

87
X Cupressocyparis leylandii
88
Biology of Propagation
  • Interfamilial hybrid- interbreeding between
    families (to date, impossible!)
  • However, recently (in 2000), plants of two
    different families were grafted together.
  • Cactaceae and Capparaceae

89
Biology of Propagation
  • Another example
  • X Fatshedera lizei
  • Parentage
  • Fatsia japonica Moseri x Hedera helix
    Hibernica

90
Fatsia japonica
91
Hedera helix
92
X Fatshedera lizeii
93
Why??
94
Biology of Propagation
  • Cultivar a cultivated variety that has
    distinguishing characteristics that make it
    different from the species
  • Usually reproduced asexually (clones)
  • If reproduced sexually, it must retain the
    distinguishing characteristics (typically done by
    careful breeding in annuals and vegetables)

95
Biology of Propagation
  • Examples of cultivars include
  • Prunus subhirtella Autumnalis
  • Prunus subhirtella cv. Autumnalis

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97
Biology of Propagation
  • Legal protection of a cultivar
  • Patent 20 years (formerly 17 years)
  • Must be vegetatively propagated
  • You cannot patent a wild-collected plant but you
    can grow it in cultivation, demonstrate that you
    can propagate it and then you can patent it!
  • Trademark protects the name, symbol, logo
    forever. You can collect royalties on plants
    with trademarked names!

98
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99
Biology of Propagation
  • What you should do when you patent a plant is to
    give it a crazy name
  • Rhododendron calendulaceum Ugly
  • Then register the trademark name for this plants
    as
  • Green and Gold rhododendron
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