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6/26/2014
Bi 151
Plant Morpho-anatomy
Lecture 1
What are plants???
Plants: General Structural Features
Jan Lorie M. Robil, M.Sc.
Kingdom Plantae (plants)
1.
2.
3.
4.
Multicellular
Autotrophs (chloroplasts)
Cellulose in cell walls
Eukaryotic (true nucleus; DNA enclosed
by a membrane)
What are some structural
features of plants?
1. Cellulosic cell walls
2. Chloroplasts
3. Appearance
a. Can include stems, leaves, and roots
b. Some lack true stems, leaves, and roots
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Flowering Plants
ANGIOSPERMS
Magnoliids
Eudicots
Monocots
White Champaca
Waling-waling
Jade vine
Shoot and Root systems
Shoot system
Basic Morphology
• above or below ground
• no clear demarcation
• morphology and anatomy are somewhat
continuous
• adventitious parts
Leaf
Leaves
Jatropha curcas
Alamanda cathartica
Stem
Leaves-modifications
Casuarina equisetifolia
Schefflera odorata
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Leaf shape
Leaf shape
A. Elliptic
B. Obovate
C. Ovate
D. Lanceolate
E. Reniform
F. Cordate
G. Trullate
H. Deltoid
I. Rhomboid
J. Amplexicaul
K. Perfoliate
L. Connate-perfoliate
M. Ensiform
N. Ligulate
O. Sagittate
P. Plated
Leaf venation
Psidium guajava
Citrus sp.
Bauhinia purpurea
Hibiscus sp.
Leaf venation
parallel venation
acrodromous venation
Eudicot
Stem
Monocot
Miconia sp.
Bambusa sp.
Stem - modifications
tubers
stolon
rhizome
tendril
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Roots
Plant Cells and Tissues
An Evolutionary Perspective
Plants are structurally complex
Plants Arose from the Green Algae
• All the cells of a plant are genetically
identical
• But the information is expressed in
different ways in different places at
different times in a synchronized fashion
• Silurian Period Over 400 Million Years Ago
... but plants arose from structurally simple
ancestors
Evidence That Plants Arose from
the Green Algae
• Pigmentation
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Evidence That Plants Arose from
the Green Algae
Evidence That Plants Arose from
the Green Algae
• Pigmentation
• Cellulose in their
cell walls
• Pigmentation
• Cellulose in their
cell walls
• Starch stored in
the plastid
• Some green algae
undergo cell
division by means
of a phragmoplast
Evidence That Plants Arose from
the Green Algae
• Pigmentation
• Cellulose in their
cell walls
• Starch stored in
the plastid
• Some green algae
undergo cell
division by means
of a phragmoplast
The structural complexity of
plants evolved in response to the
challenges of life on land
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Plants can be
considered simply
as a group of the
green algae that have
become adapted for
life on land.
Challenges for Colonizing the Land
Solutions (Adaptations)
Dehydration
Dehydration
Dermal tissue; Cuticle
Support
Support
Secondary Walls
Transport of
Water and Minerals
Transport of
Water and Minerals
Xylem Tissue
Transport of
Photosynthate
Transport of
Photosynthate
Phloem Tissue
Fertilization
Fertilization
Reproductive organs
Ground Tissue System
Vascular plants are made up of
three tissue systems which are
represented in each plant organ.
• Includes cells and tissues like those found
in the green algae
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Dermal Tissue System
• found in all plants
Dermal tissue of
a hornwort, a
non-vascular
plant
Vascular Tissue System
• Are tissues
that transport
substances
long distances
in a plant.
Cells and Tissues of the Ground
Tissue System
Green
Algae
All
Plants
Parenchyma
Collenchyma
Sclerenchyma
Parenchyma
• Parenchyma cells are living,
undifferentiated plant cells usually lacking a
secondary cell wall.
• Typically, parenchyma cells are totipotent.
– Each cell retains the ability to grow into a
whole plant.
– This makes genetic engineering much easier
with plants than with animals.
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Parenchyma Tissue
• Function
– Growth/Wound Healing/Reproduction
Parenchyma Tissue
• Functions
– Growth/Wound Healing/Reproduction
– Photosynthesis
Parenchyma Tissue
• Functions
– Growth/Wound Healing/Reproduction
– Photosynthesis
– Storage
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Collenchyma Tissue
• Is a simple tissue consisting only of
collenchyma cells
• Collenchyma cells are living cells with
thickened primary walls.
• They never have secondary walls.
Collenchyma Tissue
Collenchyma Tissue
• Support in herbaceous tissues
• Flexebility
• Support in herbaceous tissues
400x
Collenchyma acts in opposition to turgor pressure,
And, together, they lend rigidity to the plant
Sclerenchyma Tissue
• Sclerenchyma (hard) cells develop a
secondary wall, and are not involved in
transport.
• Sclerenchyma lends integrity to plant
tissues, and/or they serve to support and
protect the plant.
• There are two types of sclerenchyma cells.
– Fibers
– Sclereids
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Fibers
Sclereids
Brachysclereids
Unbranched Sclereids
Branched Sclereids (astrosclereids)
Ground Tissue System
• Includes:
– Parenchyma cells and tissue
– Collenchyma cells and tissue
– Sclerenchyma cells and tissue
• These are not exclusively found in the
ground tissue
Dermal Tissue System
Dermal Tissue System
• In herbaceous plants, an epidermis makes
up the dermal tissue system.
• Cell types of the epidermis
• Basal Cells of the Epidermis of the Shoot
– Basal Cells of the Epidermis
As the cuticle is air-tight as well as water-proof it must
be perforated to allow for gas exchange.
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If these openings are bounded by guard cells
then these are called stomata.
Dermal Tissue System
• Herbaceous plants have an epidermis. In
the shoot, the epidermis includes
– basal cells and guard cells
Dermal Tissue System
• Mature woody plant
– the epidermis is replaced by a periderm.
Periderms include cork which functions like
the epidermis in retaining water.
The word “cell” was first used in a biological
context in 1665 by Robert Hooke to describe
the units that make up the tissue of a wine cork.
Cork Tissue is Water-proof
Dermal Tissue System
• Tissues and structures
– Herbaceous growth (primary)
• Epidermis (including basal cells and guard cells)
– Cuticle (cutin)
– Wood growth (secondary)
• Periderm with cork tissue
– Suberin
Suberin
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Green
Algae
All
Plants
Vascular plants
have cells with secondary
walls that include lignin
Vascular
tissue is
necessary
for a plant
to become
tall.
But why not simply remain short?
The Vascular Tissue System
includes two types of tissues .
Because of competition for light.
Xylem
Phloem
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Vascular Tissue System
Xylem
• complex tissues
• Moves water
and minerals
up the plant
• and provides
support to
the plant.
– they are made up of more than one cell type.
– Simple tissues are made of one cell type such
as parenchyma, collenchyma and
sclerenchyma tissues.
Phloem
Moves
photosynthate
(usually sucrose)
around the plant
Evolution of Xylem and Phloem
The evolution of xylem is a direct response to the unique
challenges of life on land relating to water transport and
support.
The evolution of phloem is not specific to the challenges of
life on land, but was simply a response to the challenge of
becoming a large photo-autotroph.
Large photo-autotrophs invariably need to fuel a significant
amount of non-photosynthetic tissue.
MacArthur Highway through Dau, Mabalacat, Pampanga Province, Luzon Island, Philippines
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Xylem
• Xylem is a complex tissue that includes
tracheary elements
– Tracheary elements are dead at maturity and
have always have a secondary wall.
– Water moves through these cells by mass
flow.
– The pressure inside tracheary elements is
less than the ambient pressure and the
secondary walls prevent the cells from
collapsing.
Cohesion-Tension Theory
Role of Secondary Walls
• Water is pulled up the tracheary elements,
because water molecules stick together
(cohere) via hydrogen bonds
• adhesion of water molecules to inner cell
wall surface
• Secondary walls keep
the tracheary
elements from
collapsing
• help support the plant
• forms pits (holes) in
the wall
Vessel elements in an
elongating plant stem
Tracheary Elements
• Two types
– Vessels
– Tracheids
• both have pits (holes)
• but only vessels have
perforations
A perforation is an area between
tracheary elements where both the
primary and secondary wall has
been removed.
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Vessels
Phloem
• Vessels have independently evolved in six
different plant groups.
• a complex tissue that includes sieve
elements
– Flowering plants have them (Angiosperms)
– Conifers Don’t (Gymnosperms)
Sieve Cells (Conifers)
Sieve-Tube Elements
• made up of
sieve-tube members
Sieve-Tube Elements
(Angiosperms)
Gymnosperms have a
different type of sieve
element called a sieve cell
- Associated with albuminous cells
– have sieve plates
– and are associated
with companion cells
Vascular Tissue System
Xylem
Always includes tracheary elements
Vascular Tissue System
Phloem Always has sieve elements
If sieve-tube members then also companion cells
If sieve cells then also albuminous cells
Tracheids and/or vessel elements
May have
Parenchyma
May also have
Parenchyma cells
Fibers
Fibers
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