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Plant Structure, Growth, and Development

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Chapter 35 Plant Structure, Growth, and Development * Figure 35.18 Leaf anatomy. * * * Figure 35.10 Exploring: Examples of Differentiated Plant Cells * * Figure 35.10 ... – PowerPoint PPT presentation

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Title: Plant Structure, Growth, and Development


1
Chapter 35
Plant Structure, Growth, and Development
2
Overview Are Plants Computers?
  • Romanesco grows according to a repetitive program
  • The development of plants depends on the
    environment and is highly adaptive

3
Concept 35.1 Plants have a hierarchical
organization consisting of organs, tissues, and
cells
  • Plants have organs composed of different tissues,
    which in turn are composed of different cell
    types
  • A tissue is a group of cells consisting of one or
    more cell types that together perform a
    specialized function
  • An organ consists of several types of tissues
    that together carry out particular functions

4
The Three Basic Plant Organs Roots, Stems, and
Leaves
  • Basic morphology of vascular plants reflects
    their evolution as organisms that draw nutrients
    from below ground and above ground
  • Plants take up water and minerals from below
    ground
  • Plants take up CO2 and light from above ground

5
  • Three basic organs evolved roots, stems, and
    leaves
  • They are organized into a root system and a shoot
    system

6
Figure 35.2
Reproductive shoot (flower)
Apical bud
Node
Internode
Apical bud
Shoot system
Axillary bud
Vegetative shoot
Blade
Leaf
Petiole
Stem
Taproot
Root system
Lateral (branch)roots
7
  • Roots rely on sugar produced by photosynthesis in
    the shoot system, and shoots rely on water and
    minerals absorbed by the root system
  • Monocots and eudicots are the two major groups of
    angiosperms

8
Roots
  • A root is an organ with important functions
  • Anchoring the plant
  • Absorbing minerals and water
  • Storing carbohydrates

9
  • Most dicots and gymnosperms have a taproot
    system, which consists of
  • A taproot, the main vertical root
  • Lateral roots, or branch roots, that arise from
    the taproot
  • Most monocots have a fibrous root system, which
    consists of
  • Adventitious roots that arise from stems or
    leaves
  • Lateral roots that arise from the adventitious
    roots

10
  • In most plants, absorption of water and minerals
    occurs near the root hairs, where vast numbers of
    tiny root hairs increase the surface area

11
Figure 35.3
12
  • Many plants have root adaptations with
    specialized functions

13
Figure 35.4a
Prop roots
14
Figure 35.4b
Storage roots
15
Figure 35.4c
Strangling aerial roots
16
Figure 35.4d
Pneumatophores
17
Figure 35.4e
Buttress roots
18
Stems
  • A stem is an organ consisting of
  • An alternating system of nodes, the points at
    which leaves are attached
  • Internodes, the stem segments between nodes

19
  • An axillary bud is a structure that has the
    potential to form a lateral shoot, or branch
  • An apical bud, or terminal bud, is located near
    the shoot tip and causes elongation of a young
    shoot
  • Apical dominance helps to maintain dormancy in
    most axillary buds

20
  • Many plants have modified stems (e.g., rhizomes,
    bulbs, stolons, tubers)

21
Figure 35.5a
Rhizome
Root
Rhizomes
22
Figure 35.5b
Storage leaves
Stem
Bulbs
23
Figure 35.5c
Stolon
Stolons
24
Figure 35.5d
Tubers
25
Leaves
  • The leaf is the main photosynthetic organ of most
    vascular plants
  • Leaves generally consist of a flattened blade and
    a stalk called the petiole, which joins the leaf
    to a node of the stem

26
  • Monocots and eudicots differ in the arrangement
    of veins, the vascular tissue of leaves
  • Most monocots have parallel veins
  • Most eudicots have branching veins
  • In classifying angiosperms, taxonomists may use
    leaf morphology as a criterion

27
Figure 35.6
Simple leaf
Axillarybud
Petiole
Compound leaf
Doublycompound leaf
Leaflet
Petiole
Axillarybud
Axillarybud
Leaflet
Petiole
28
  • Some plant species have evolved modified leaves
    that serve various functions

29
Figure 35.7
Tendrils
Spines
Storageleaves
Reproductiveleaves
Bracts
30
Dermal, Vascular, and Ground Tissues
  • Each plant organ has dermal, vascular, and ground
    tissues
  • Each of these three categories forms a tissue
    system
  • Each tissue system is continuous throughout the
    plant

31
Figure 35.8
Dermaltissue
Groundtissue
Vasculartissue
32
  • In nonwoody plants, the dermal tissue system
    consists of the epidermis
  • A waxy coating called the cuticle helps prevent
    water loss from the epidermis
  • In woody plants, protective tissues called
    periderm replace the epidermis in older regions
    of stems and roots
  • Trichomes are outgrowths of the shoot epidermis
    and can help with insect defense

33
Figure 35.9
EXPERIMENT
Very hairy pod(10 trichomes/mm2)
Slightly hairy pod(2 trichomes/mm2)
Bald pod(no trichomes)
RESULTS
Very hairy pod10 damage
Slightly hairy pod25 damage
Bald pod40 damage
34
Figure 35.9a
35
  • The vascular tissue system carries out
    long-distance transport of materials between
    roots and shoots
  • The two vascular tissues are xylem and phloem
  • Xylem conveys water and dissolved minerals upward
    from roots into the shoots
  • Phloem transports organic nutrients from where
    they are made to where they are needed

36
  • The vascular tissue of a stem or root is
    collectively called the stele
  • In angiosperms the stele of the root is a solid
    central vascular cylinder
  • The stele of stems and leaves is divided into
    vascular bundles, strands of xylem and phloem

37
  • Tissues that are neither dermal nor vascular are
    the ground tissue system
  • Ground tissue internal to the vascular tissue is
    pith ground tissue external to the vascular
    tissue is cortex
  • Ground tissue includes cells specialized for
    storage, photosynthesis, and support

38
Common Types of Plant Cells
  • Like any multicellular organism, a plant is
    characterized by cellular differentiation, the
    specialization of cells in structure and function

39
  • The major types of plant cells are
  • Parenchyma
  • Collenchyma
  • Sclerenchyma
  • Water-conducting cells of the xylem
  • Sugar-conducting cells of the phloem

40
Parenchyma Cells
  • Mature parenchyma cells
  • Have thin and flexible primary walls
  • Lack secondary walls
  • Are the least specialized
  • Perform the most metabolic functions
  • Retain the ability to divide and differentiate

41
Figure 35.10a
Parenchyma cells in Elodealeaf, with
chloroplasts (LM)
60 ?m
42
Collenchyma Cells
  • Collenchyma cells are grouped in strands and help
    support young parts of the plant shoot
  • They have thicker and uneven cell walls
  • They lack secondary walls
  • These cells provide flexible support without
    restraining growth

43
Figure 35.10b
Collenchyma cells(in Helianthus stem) (LM)
5 ?m
44
Sclerenchyma Cells
  • Sclerenchyma cells are rigid because of thick
    secondary walls strengthened with lignin
  • They are dead at functional maturity
  • There are two types
  • Sclereids are short and irregular in shape and
    have thick lignified secondary walls
  • Fibers are long and slender and arranged in
    threads

45
Figure 35.10c
5 ?m
Sclereid cells in pear (LM)
25 ?m
Cell wall
Fiber cells (cross section from ash tree) (LM)
46
Figure 35.10ca
5 ?m
Sclereid cells in pear (LM)
Cell wall
47
Figure 35.10cb
25 ?m
Fiber cells (cross section from ash tree) (LM)
48
Water-Conducting Cells of the Xylem
  • The two types of water-conducting cells,
    tracheids and vessel elements, are dead at
    maturity
  • Tracheids are found in the xylem of all vascular
    plants

49
  • Vessel elements are common to most angiosperms
    and a few gymnosperms
  • Vessel elements align end to end to form long
    micropipes called vessels

50
Figure 35.10d
100 ?m
Vessel
Tracheids
Tracheids and vessels(colorized SEM)
Pits
Perforationplate
Vessel element
Vessel elements, withperforated end walls
Tracheids
51
Sugar-Conducting Cells of the Phloem
  • Sieve-tube elements are alive at functional
    maturity, though they lack organelles
  • Sieve plates are the porous end walls that allow
    fluid to flow between cells along the sieve tube
  • Each sieve-tube element has a companion cell
    whose nucleus and ribosomes serve both cells

52
Figure 35.10e
Sieve-tube elementslongitudinal view (LM)
3 ?m
Sieve plate
Sieve-tube element (left)and companion
cellcross section (TEM)
Companioncells
Sieve-tubeelements
Plasmodesma
Sieve plate
30 ?m
Nucleus ofcompanioncell
15 ?m
Sieve-tube elementslongitudinal view
Sieve plate with pores (LM)
53
Figure 35.10ed
Sieve-tubeelements
Plasmodesma
Sieve plate
Nucleus ofcompanioncell
Sieve-tube elementslongitudinal view
54
Concept 35.2 Meristems generate cells for
primary and secondary growth
  • A plant can grow throughout its life this is
    called indeterminate growth
  • Some plant organs cease to grow at a certain
    size this is called determinate growth

55
  • Meristems are perpetually embryonic tissue and
    allow for indeterminate growth (MITOSIS)
  • Apical meristems are located at the tips of roots
    and shoots and at the axillary buds of shoots
  • Apical meristems elongate shoots and roots, a
    process called primary growth

56
  • Lateral meristems add thickness to woody plants,
    a process called secondary growth
  • There are two lateral meristems the vascular
    cambium and the cork cambium
  • The vascular cambium adds layers of vascular
    tissue called secondary xylem (wood) and
    secondary phloem
  • The cork cambium replaces the epidermis with
    periderm, which is thicker and tougher

57
Figure 35.11
Primary growth in stems
Epidermis
Cortex
Primary phloem
Shoot tip (shootapical meristemand young leaves)
Primary xylem
Pith
Vascular cambium
Secondary growth in stems
Lateralmeristems
Corkcambium
Cork cambium
Axillary budmeristem
Cortex
Periderm
Primary phloem
Secondary phloem
Pith
Root apicalmeristems
Primaryxylem
Vascular cambium
Secondary xylem
58
  • Meristems give rise to
  • Initials, also called stem cells, which remain in
    the meristem
  • Derivatives, which become specialized in mature
    tissues
  • In woody plants, primary growth and secondary
    growth occur simultaneously but in different
    locations

59
Figure 35.12
Apical bud
Bud scale
Axillary buds
This years growth(one year old)
Leafscar
Node
Budscar
One-year-old sidebranch formedfrom axillary
budnear shoot tip
Internode
Last years growth(two year old)
Leaf scar
Stem
Bud scar
Growth of twoyears ago(three years old)
Leaf scar
60
  • Flowering plants can be categorized based on the
    length of their life cycle
  • Annuals complete their life cycle in a year or
    less
  • Biennials require two growing seasons
  • Perennials live for many years

61
Concept 35.3 Primary growth lengthens roots and
shoots
  • Primary growth produces the parts of the root and
    shoot systems produced by apical meristems

62
Primary Growth of Roots
  • The root tip is covered by a root cap, which
    protects the apical meristem as the root pushes
    through soil
  • Growth occurs just behind the root tip, in three
    zones of cells
  • Zone of cell division
  • Zone of elongation
  • Zone of differentiation, or maturation

63
Figure 35.13
Vascular cylinder
Cortex
Keyto labels
Epidermis
Dermal
Ground
Zone ofdifferentiation
Root hair
Vascular
Zone of elongation
Mitoticcells
Zone of celldivision(includingapicalmeristem)
100 ?m
Root cap
64
  • The primary growth of roots produces the
    epidermis, ground tissue, and vascular tissue
  • In angiosperm roots, the stele is a vascular
    cylinder
  • In most eudicots, the xylem is starlike in
    appearance with phloem between the arms
  • In many monocots, a core of parenchyma cells is
    surrounded by rings of xylem then phloem

65
Figure 35.14
Epidermis
Cortex
Endodermis
Vascularcylinder
Pericycle
Core ofparenchymacells
Xylem
100 ?m
Phloem
100 ?m
(a)
Root with xylem andphloem in the center(typical
of eudicots)
(b)
Root with parenchyma in thecenter (typical of
monocots)
50 ?m
Key to labels
Endodermis
Pericycle
Dermal
Xylem
Ground
Phloem
Vascular
66
  • The ground tissue, mostly parenchyma cells, fills
    the cortex, the region between the vascular
    cylinder and epidermis
  • The innermost layer of the cortex is called the
    endodermis
  • The endodermis regulates passage of substances
    from the soil into the vascular cylinder

67
  • Lateral roots arise from within the pericycle,
    the outermost cell layer in the vascular cylinder

68
Figure 35.15-3
Epidermis
100 ?m
Emerginglateralroot
Lateral root
Cortex
Vascular cylinder
Pericycle
69
Primary Growth of Shoots
  • A shoot apical meristem is a dome-shaped mass of
    dividing cells at the shoot tip
  • Leaves develop from leaf primordia along the
    sides of the apical meristem
  • Axillary buds develop from meristematic cells
    left at the bases of leaf primordia

70
Figure 35.16
Shoot apical meristem
Leaf primordia
Youngleaf
Developingvascular strand
Axillary budmeristems
0.25 mm
71
Tissue Organization of Stems
  • Lateral shoots develop from axillary buds on the
    stems surface
  • In most eudicots, the vascular tissue consists of
    vascular bundles arranged in a ring

72
Figure 35.17
Phloem
Xylem
Sclerenchyma(fiber cells)
Ground tissue
Ground tissueconnectingpith to cortex
Pith
Epidermis
Keyto labels
Cortex
Epidermis
Vascularbundles
Vascularbundle
Dermal
1 mm
1 mm
Ground
(a)
(b)
Cross section of stem withvascular bundles
forming aring (typical of eudicots)
Cross section of stem withscattered vascular
bundles(typical of monocots)
Vascular
73
Figure 35.17a
Phloem
Xylem
Sclerenchyma(fiber cells)
Ground tissueconnectingpith to cortex
Pith
Keyto labels
Epidermis
Cortex
Dermal
Vascularbundle
Ground
1 mm
Vascular
(a)
Cross section of stem with vascular bundles
forming a ring (typical of eudicots)
74
  • In most monocot stems, the vascular bundles are
    scattered throughout the ground tissue, rather
    than forming a ring

75
Figure 35.17b
Ground tissue
Keyto labels
Dermal
Ground
Vascular
Epidermis
Vascularbundles
1 mm
(b)
Cross section of stem with scattered vascular
bundles (typical of monocots)
76
Tissue Organization of Leaves
  • The epidermis in leaves is interrupted by
    stomata, which allow CO2 and O2 exchange between
    the air and the photosynthetic cells in a leaf
  • Each stomatal pore is flanked by two guard cells,
    which regulate its opening and closing
  • The ground tissue in a leaf, called mesophyll, is
    sandwiched between the upper and lower epidermis

77
  • The mesophyll of eudicots has two layers
  • The palisade mesophyll in the upper part of the
    leaf
  • The spongy mesophyll in the lower part of the
    leaf the loose arrangement allows for gas
    exchange

78
  • The vascular tissue of each leaf is continuous
    with the vascular tissue of the stem
  • Veins are the leafs vascular bundles and
    function as the leafs skeleton
  • Each vein in a leaf is enclosed by a protective
    bundle sheath

79
Figure 35.18
Guard cells
Keyto labels
Stomatalpore
Dermal
Ground
Epidermalcell
50 ?m
Vascular
Sclerenchymafibers
(b)
Surface view ofa spiderwort(Tradescantia)leaf
(LM)
Cuticle
Stoma
Upperepidermis
Palisademesophyll
Spongymesophyll
Bundle-sheathcell
Lowerepidermis
100 ?m
Xylem
Cuticle
Vein
Guard cells
Phloem
Guardcells
Air spaces
Vein
(c)
Cross section of a lilac(Syringa) leaf (LM)
(a) Cutaway drawing of leaf tissues
80
Figure 35.18a
Keyto labels
Sclerenchymafibers
Cuticle
Dermal
Stoma
Ground
Vascular
Upperepidermis
Palisademesophyll
Spongymesophyll
Bundle-sheathcell
Lowerepidermis
Xylem
Cuticle
Vein
Phloem
Guardcells
(a) Cutaway drawing of leaf tissues
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