Lecture

1
Lecture 4 Plant Structure, Growth And
Development
Image the Angel Oak
2
Key Concepts

• What is a kingdom?
• Why study plants?
• What makes a plant a plant?
• The hierarchy of structure plant cells, tissues
  and organs
• Growth
• Primary growth elongation
• Secondary growth diameter expansion
• Morphogenesis occurs during growth

3
Carolus Linnaeus (1707-1778) The founder of
modern taxonomy defined kingdoms by morphological
similarity
Image Linnaeus
4
Linnaeus Taxonomic Hierarchy
5
Linnaeus Taxonomic Hierarchy
6
Images the yellow fringed orchid
Platanthera ciliaris
7

• Linnaeus recognized only 2 kingdoms
• If it moved animal if it didnt plant
• Fungi were lumped with plants
• The microscopic world was largely unknown

Images the 3 multicellular kingdoms, animals,
fungi and plants
8
The 5 kingdom system developed in the 1960s
and used until recently
Diagram the 5 kingdom system
9
Molecular data supports 3 domain classification
scheme
Diagram 3 domain system of classification
Kingdoms are defined by monophyletic lineage
10
Classification is Dynamic!
Diagram transition from 5 kingdom to 3 domain
system indicating dynamic nature of classification
Multicellular eukaryotes remain fairly well
defined the plants, fungi and animals.
Classification of single celled organisms is
still underway.
11
Current Taxonomic Hierarchy
12
Why Plants?
13
Why Plants?

• Food
• Pharmaceuticals
• Building materials
• Furniture
• Paper
• Chemicals
• Horticulture/Floriculture
• etc..

Image shooting stars
14
What makes a plant a plant???
15
Images and diagrams characteristics that
separate plants from other kingdoms
16
What makes a plant a plant???

• Multicellular, eukaryotic organisms with
  extensive specialization
• Almost all are photosynthetic, with chloroplasts
  ( green)
• Some obtain additional nutrition through
  parasitism or carnivory
• Some are saprophytic, entirely without
  chlorophyll (absorb dead OM)
• Excess carbohydrates stored as starch (coiled,
  branched polymer of glucose)
• Cell walls of cellulose fibrous (not branched)
  polysaccharide accounts for the relative
  rigidity of the cell wall
• Cell division by formation of cell plate
• Most extant plant species are terrestrial (many
  characteristics that are adapted for terrestrial
  life)
• Separated from cyanobacteria by chloroplasts
• Separated from green algae by various adaptations
  to terrestrial life

Read this later.
17
Plants were the first organisms to move onto land

• Occurred about 475mya
• Very different conditions from former marine
  habitat
• Many new traits emerged in adaptation to life on
  dry land
• Extensive adaptive radiation into many new
  ecological niches

18
Diagram phylogeny of land plants same on next
slide
Four major groups of plants have emerged since
plants took to land
19
We will focus on angiosperms Next semester in
211 you will learn more about the transition from
water to land, and the evolution of reproductive
strategies in all plants
20
Angiosperms the flowering plants90 of the
Earths modern flora
Images flowering plants
21
Basic Structure of the Plant Cell whats
unique???
Diagram plant cell same on next slide
22
Basic Structure of the Plant Cell
23
Critical Thinking

• Do all plant cells have chloroplasts???
• How can you tell???

24
Critical Thinking

• Do all plant cells have chloroplasts???
• NO!!!
• How can you tell???

25
Critical Thinking

• Do all plant cells have chloroplasts???
• NO!!!
• How can you tell???
• Chlorophyll reflects green light
• Green tissues have chloroplasts
• Non-green tissues dont

Image chloroplast free white bracts on
white-top sedge
26
More on the cell wall

• All cell walls are produced by the cell membrane,
  outside
• Primary wall is produced first
• Mostly cellulose
• Secondary walls are produced later
• Lignified, so ???
• Secondary walls are interior to primary walls

Diagram primary and secondary cell walls same
on next slide
27
More on the cell wall

• All cell walls are produced by the cell membrane
• Primary wall is produced first
• Mostly cellulose
• Secondary walls are produced later
• Lignified, so rigid!
• Secondary walls are interior to primary walls

28
Five Major Plant Cell Types
Micrographs plant cell types

• Parenchyma
• Collenchyma
• Sclerenchyma
• Xylem elements
• Phloem elements

29
Parenchyma

• Thin primary wall
• No secondary wall
• Many metabolic and storage functions
• Bulk of the plant body

Micrographs parenchyma cells
30
Collenchyma

• Thick primary wall
• No secondary wall
• Implications???
• Support growing tissues

Micrograph collenchyma cells same on next slide
31
Collenchyma

• Thick primary wall
• No secondary wall
• Extensible no lignin means they can elongate
• Support growing tissues

32
Sclerenchyma

• Thick secondary wall
• Secondary walls are lignified
• Implications???
• Support mature plant parts
• Often dead at maturity

Micrograph sclerenchma cells same on next slide
33
Sclerenchyma

• Thick secondary wall
• Secondary walls are lignified
• Lignified cells are rigid and fixed in size
• Support mature plant parts
• Often dead at maturity

34
Collenchyma vs. Sclerenchyma

• Both provide structural support
• Both have thick walls
• Collenchyma thick primary wall, no lignin
• Sclerenchyma thick secondary wall, lignified

Micrographs collenchyma and sclerenchyma cell
comparison
35
Xylem Elements
Diagrams and micrograph tracheids and vessel
elements

• Lignified secondary walls
• Always dead at maturity (open)
• Function to transport water and dissolved
  nutrients, and to support the plant
• Tracheids and vessel elements

36
Critical Thinking
Micrograph rings of lignin in developing vessel
element same on next slide

• Vessel elements and the convergent evolution of
  rings
• What else looks like this????
• What is the function????

37
Critical Thinking

• Vessel elements and the convergent evolution of
  rings
• What else looks like this????
• What is the function????
• Stiff rings hold the tube open
• Trachea in both vertebrates and inverts

38
Phloem Elements

• Sieve tube members companion cells
• STM lack nucleus, ribosomes their metabolism is
  controlled by the companion cells
• Function to transport the products of metabolism
• Non-angiosperms have more primitive phloem
  elements

Micrograph phloem elements
39
Critical Thinking

• What might be the functional advantage of a cell
  with no nucleus???

Diagram phloem elements
40
Critical Thinking

• What might be the functional advantage of a cell
  with no nucleus???
• Sieve plates are very open
• Plus, function is to move large volumes of sap
  around the plant
• Nucleus and other organelles get in the way
• But, phloem transport requires ATP and thus a
  living cell

41
Plants are Simple ? Only Five Major Cell Types
Micrographs plant cell types

• Parenchyma
• Collenchyma
• Sclerenchyma
• Xylem elements
• Phloem elements

42
Tissue Systems
Diagram plant tissue types

• Epidermis
• Vascular
• Ground
• Meristem

43
Epidermis Tissue

• Covers the outer surface of all plant parts
• Shoot surfaces covered with waxy cuticle
• Helps to protect the plant and prevent
  desiccation
• Usually a single, transparent cell layer
• Tight joints stomata allow for gas exchange

Micrograph and diagram epidermis
44
Critical Thinking

• Do roots have a waxy cuticle???
• Why or why not???

45
Critical Thinking

• Do roots have a waxy cuticle???
• No
• Why or why not???
• Wax is waterproof
• Roots absorb water from the soil
• A waxy coating would be a functional DISadvantage

Never forget the importance of natural
selection!!!!!
46
Vascular Tissue

• Transports water, solutes, and metabolic products
  throughout the plant
• Confers structural support
• Includes xylem elements, phloem elements,
  parenchyma and sclerenchyma fibers

Micrograph vascular bundle in cross section
47
Critical Thinking

• Why does vascular tissue give structural support
  to a plant???

48
Critical Thinking

• Why does vascular tissue give structural support
  to a plant???
• LIGNIN
• Xylem and sclerenchyma fibers are lignified!

49
Ground Tissue

• Bulk of the plant body pith, cortex and
  mesophyll
• Mostly parenchyma
• Most metabolic, structural and storage functions

Micrograph and diagram ground tissues in stems
and leaves
50
Critical Thinking

• Is this what the inside of a tree looks like???

Micrograph herbaceous dicot stem
51
Critical Thinking

• Is this what the inside of a tree looks like???
• No wood is xylem tissue
• The bulk of a tree is wood, not ground tissue

Micrograph of herbaceous eudicot stem image of
woody stem diagram of woody stem tissue
organization
52
Meristem Tissue

• How the plant grows
• Cells divide constantly during the growing season
  to make new tissues
• More details later

Image new growth at tip of stem
53
Plants are Simple ?Only Four Major Tissue Types
Diagram plant tissue systems

• Epidermis
• Vascular
• Ground
• Meristem

54
Tissues Make Organs

• Roots anchor the plant, absorb water and
  nutrients
• Stems support the leaves
• Leaves main site of photosynthesis
• Reproductive organs (flowers, cones, etc more
  later)

All organs have additional functions hormone
synthesis, transport, etc
55
Plant Organ Systems
Diagram root and shoot systems
56
Modern molecular evidence indicates four classes
of angiosperms
57
Paleoherbs and Magnoliids comprise about 3 of
angiosperms

• Paleoherbs
• Aristolochiaceae, Nymphaeaceae, etc

• Magnoliids
• Magnoliaceae, Lauraceae, nutmeg, black pepper, etc

Images water lily and magnolia
58
Modern evidence indicates 4 classes of angiosperms
97 of angiosperms
59
Monocots include grasses, sedges, iris, orchids,
lilies, palms, etc..
Images monocots
60
Eudicots include 70 of all angiosperms

• Most broadleaf trees and shrubs
• Most fruit and vegetable crops
• Most herbaceous flowering plants

Images eudicots
61
Monocots vs. Eudicots

• Monocots
• Flower parts in multiples of 3
• Parallel leaf venation
• Single cotyledon
• Vascular bundles in complex arrangement
• 90,000 species

• Eudicots
• Flower parts in multiples of 4 or 5
• Netted leaf venation
• Two cotyledons
• Vascular bundles in a ring around the stem
• Modern classification indicates 2 small primitive
  groups eudicots
• 200,000 species

62
Root System Tissue Organization
Eudicots
Monocots
Micrographs cross sections of eudicot and
moncot roots same on next 3 slides
Epidermis, ground, endodermis, pericycle,
vascular tissues
63
Eudicot root closeup
Epidermis Cortex Endodermis Pericycle Vascular
tissues in solid core
64
Monocot root closeup
Epidermis Cortex Endodermis Pericycle Vascular
tissues in ring Pith in the very center
65
Critical Thinking

• Where do branch roots form???

66
Critical Thinking

• Where do branch roots form???
• The pericycle is the meristem tissue
• Roots branch from the inside and push their way
  out

Micrograph root emerging from pericycle
67
Stem System Tissue Organization
Eudicots
Monocots
Micrograph eudicot and monocot stem tissue
organization same on next 4 slides
Epidermis, ground, vascular tissues
68
Eudicot stem closeup
Epidermis Cortex Vascular tissues bundles in
a ring Pith
69
Monocot stem closeup
Epidermis Cortex Vascular tissues
bundles are scattered
70
Wood forms from a meristem that links the
vascular bundles
71
Stem System Tissue Organization
Eudicots
Monocots
Monocots cannot make wood
More on wood formation later
72
Leaf Tissue Arrangement
Micrograph cross-section of leaf tissue
arrangement
Epidermis, ground, vascular tissues
73
Leaf closeup
Epidermis Cortex palisade mesophyll Cortex
spongy mesophyll Vascular tissues
Diagram leaf tissue arrangement
74
Stomata pores to allow for gas exchange and
transpiration
Micrograph epidermis tissue showing stomata
75
See, plants really are simple ?

• 5 cell types
• 4 tissue types
• 4 organ types

Diagram shoot and root systems
76
Plant Growth

• Remember, most plants are anchored by roots
• They cant move to escape or take advantage of
  changes in their environment
• Plants adjust to their environment
• Simple structure lots of developmental
  flexibility allow plants to alter when and how
  they grow

Developmental flexibility comes from meristems
77
Meristem Tissues

• Actively dividing cells that generate all other
  cells in the plant body
• Cause indeterminate growth
• Stems and roots elongate throughout the plants
  life (indeterminate primary growth)
• Trees continually expand in diameter
  (indeterminate secondary growth)
• Branches form in roots and stems

78
Not all plant parts have indeterminate growth
patterns
Indeterminate Roots and Stems These parts grow
throughout the life of the plant, exploring new
environments or responding to damage
Determinate Leaves Flowers Fruits These parts
grow to a genetically /- predetermined size and
shape and then stop cannot repair damage
79
Some mature cells can de-differentiate to become
meristematic once more!!!

• Primarily occurs in the indeterminate parts
• Stems and roots
• A process that very seldom occurs in other
  kingdoms
• Allows stems and roots to repair damage and form
  branches and sprouts

80
Critical Thinking

• Can all plant cells de-differentiate???
• What would control this???

81
Critical Thinking

• Can all plant cells de-differentiate???
• No
• What would control this???

82
Critical Thinking

• Can all plant cells de-differentiate???
• No
• What would control this???
• Lignin!!!
• Lignin is strong and rigid
• Once a cell is lignified, it cannot expand or
  divide

83
Growth in Plantsan irreversible increase in
size due to metabolic processes(processes that
use ATP energy)

• Cell division produces new cells function of
  meristem
• Cell expansion increases the size of the new
  cells up to 80 of size increase
• Cell differentiation occurs during and after
  expansion

84
The plane of cell division contributes to
morphogenesis
Diagram planes of cell division and the effect
on morphogenesis
Division in 2 planes forms sheets of cells
85
Critical Thinking

• What tissues are files of cells???
• What tissues are sheets of cells???
• What tissues are 3-D bulky???

86
Critical Thinking

• What tissues are files of cells???
• Primary vascular tissues, sclerenchyma fibers
• What tissues are sheets of cells???
• Epidermis, secondary vascular tissues
• What tissues are 3-D bulky???
• Ground tissues pith and cortex

87
Growth in Plantsan irreversible increase in
size due to metabolic processes(processes that
use ATP energy)

• Cell division produces new cells function of
  meristem
• Cell expansion increases the size of the new
  cells up to 80 of size increase
• Cell differentiation occurs during and after
  expansion

88
Auxin-mediated cell expansion
Diagram how auxin works to promote cell
expansion
ATP is used
89
The direction of cell expansion depends on
cellulose orientation, and contributes to
morphogenesis
Diagram cellulose orientation in primary wall
and the effects on morphogenesis
90
Growth in Plantsan irreversible increase in
size due to metabolic processes(processes that
use ATP energy)

• Cell division produces new cells function of
  meristem
• Cell expansion increases the size of the new
  cells up to 80 of size increase
• Cell differentiation occurs during and after
  expansion

91
Diagram patterns of growth in roots
Expansion and differentiation occur in an
overlapping zone in all plant parts
92
REVIEW Growth in Plantsan irreversible
increase in size due to metabolic
processes(processes that use ATP energy)

• Cell division produces new cells function of
  meristem
• Cell expansion increases the size of the new
  cells up to 80 of size increase
• Cell differentiation occurs during and after
  expansion

93
Location of the meristems determines the pattern
of plant growth Most common meristems apical,
axillary and lateral
Diagram location of meristems on the plant
body next slide also
94
Apical meristems cause elongation of roots and
stems
95
Micrograph longitudinal section showing
distribution of tissues in root
96
Images root cap and mucigel
97
Root Cap

• Protects the meristem
• Secretes mucigel
• Eases movement of roots through soil
• Secretes chemicals that enhance nutrient uptake
• Constantly shedding cells
• Mechanical abrasion as roots grow through soil
• Constantly being replenished by meristem

98
Primary Growth in Roots
Diagram longitudinal section of root showing
zones of growth same on next 2 slides
99
Primary Growth in Roots
100
Primary Growth in Roots
101
Root Hairs

• Form as the epidermis fully differentiates
• Extensions off epidermal cells
• NOT files of cells
• Part of an epidermal cell
• Hugely increase the surface area of the epidermis
• 10 cubic cm (double handful) of soil might
  contain 1 m of plant roots
• Mostly root hairs

Micrograph root hairs extending from epidermis
same on next few slides
102
Critical Thinking

• What is the selective advantage of root hairs???

103
Critical Thinking

• What is the selective advantage of root hairs???
• Increased surface area allows for more absorption
  of water and nutrients
• Fine diameter allows roots to ramify throughout
  the soil environment

104
Root Hairs

• By contrast, 10 cc of soil may contain up to 1000
  m of fungal hyphae (1km!)
• These serve a similar function for the fungus
• Ramify throughout the substrate for maximum
  absorption
• Some fungi form symbiotic associations with plant
  roots and both organisms benefit from this huge
  absorptive surface area!
• More in 211..

105
Apical meristems cause elongation of roots and
stems
Diagram location of apical meristems
106
Apical Meristems in Shoots
Micrograph longitudinal section of stem showing
apical and axillary meristems
107
Critical Thinking

• There is no shoot cap why not???

108
Critical Thinking

• There is no shoot cap why not???
• No selective advantage! Shoots push through
  air essentially no friction

109
Axillary meristems allow for branching similar
in structure and function to apical
meristems Remember, pericycle in roots has same
function
Diagram meristem locations
110
Axillary Meristems in Shoots
Micrograph longitudinal section of stem showing
apical and axillary meristems same on next two
slides
111
Primary Growth in Shoots

• Apical meristem
• Leaf primordia
• Axillary buds

112
As with roots cell division occurs first zones
of expansion and differentiation
overlap Axillary buds may activate to make
branches, or may remain dormant
113
Primary growth of a shoot elongation from the
tip
Diagram how stems elongate during primary growth
114
Lateral meristems cause diameter
expansion Roots also expand in diameter, but
its more complicated well save that for BIOL
300
Diagram meristem locations
115
Lateral Meristems Cambiums
Diagram lateral meristems
116
Remember Elongation is primary growth
Diameter expansion is secondary growth
Diagram primary vs. secondary growth
117
Secondary growth diameter expansion
Images cross section of wood and whole tree
118
Eudicot Stem recall the arrangement of vascular
bundles
Micrograph cross section of a eudicot stem
same on next 2 slides
119
Eudicot Stem recall the arrangement of vascular
bundles
Vascular cambium forms here
120
Eudicot Stem recall the arrangement of vascular
bundles
Vascular cambium forms here a cylinder of
meristem tissue between the xylem to the interior
and the phloem to the exterior
121
Secondary xylem and phloem form through cell
division by the vascular cambium
Diagram location of the vascular cambium
relative to other tree tissues
122
During primary growth the vascular tissues form
in bundles from the apical meristem During
secondary growth the vascular tissues form in
cylinders from the vascular cambium 2o xylem to
the inside 2o phloem to the outside
Diagram transition from primary growth to
secondary growth same on next slide
123
Secondary xylem accumulates
124
Secondary Xylem Wood!
Micrograph cross section of woody plant showing
secondary tissues same on next slide
125
Annual growth rings are accumulating rings of
secondary xylem
126
Critical Thinking

• Why do eudicot trees taper???

Diagram pattern of accumulation of secondary
xylem as a tree grows same on next slide
127
Critical Thinking

• Why do eudicot trees taper???
• Elongation occurs from the tip
• Every year adds height to the stem
• Each new section of stem has just one layer of
  secondary growth
• The section below that has 1 layers
• The section below that has 2 layers
• The section below that has 3 layers
• etc, etc, etc
• The bottom of the tree has as many rings as the
  tree is old

128
Bark

• All tissues external to the vascular cambium
• Diameter expansion splits original epidermis
• Bark structurally and functionally replaces
  epidermis
• Inner bark
• Functional secondary phloem
• Outer bark
• Composition varies as tree matures

129
Bark Formation
Micrograph cross section of a tree showing bark
formation
130
Cork Cambium

• Meristematic tissue
• Forms in a cylinder during 2o growth
• Divides to produce cork cells
• Cells filled with waxy, waterproof suberin
• Eventually cork cambium becomes cork itself

131
More on cork cambium

• First layer develops from cortex
• De-differentiation!!!
• Second layer forms from cortex same process
• Third layer forms from cortex..
• Cortex eventually runs out
• Then what???

132
More on cork cambium

• First layer develops from cortex
• De-differentiation!!!
• Second layer forms from cortex same process
• Third layer forms from cortex..
• Cortex eventually runs out
• Then what???

133
More on cork cambium

• First layer develops from cortex
• De-differentiation!!!
• Second layer forms from cortex same process
• Third layer forms from cortex..
• Cortex eventually runs out
• Then what???

134
More on cork cambium

• First layer develops from cortex
• De-differentiation!!!
• Second layer forms from cortex same process
• Third layer forms from cortex..
• Cortex eventually runs out
• Then what???

135
Critical Thinking

• What is the next available layer of tissue???

Diagram lateral meristems and the secondary
tissues in a tree same on next slide
136
Critical Thinking

• What is the next available layer of tissue???
• Secondary phloem!

137
More on cork cambium

• First layer develops from cortex
• De-differentiation!!!
• Second layer forms from cortex same process
• Third layer forms from cortex..
• Cortex eventually runs out
• Then what???
• Cork cambium forms from 2o phloem once all the
  cortex is used up

138
More on cork cambium

• First layer develops from cortex
• De-differentiation!!!
• Second layer forms from cortex same process
• Third layer forms from cortex..
• Cortex eventually runs out
• Then what???
• Cork cambium forms from 2o phloem
• 2o phloem does NOT accumulate like 2o xylem

139
Stem Tissue Derivations and Fates
Diagram how undifferentiated cells develop into
the tissues of the plant body
Cells divide, expand and differentiate
140
Review Key Concepts

• What is a kingdom?
• Why study plants?
• What makes a plant a plant?
• The hierarchy of structure plant cells, tissues
  and organs
• Growth
• Primary growth elongation
• Secondary growth diameter expansion
• Morphogenesis occurs during growth

141
Monocots, Palmetto Trees, Ft. Moultrie and the
SC State Flag
Various images and a micrograph of a monocot stem
an example of one influence of plants on
American history