Plant Tissues and
Plant Tissues and
Organs
Organs
Topic 13 Plant Science
Topic 13 Plant Science
Subtopics 13.1.2, 13.1.3,
Subtopics 13.1.2, 13.1.3,
13.1.4
13.1.4
Plant Tissues and
Plant Tissues and
Organs
Organs
Topic 13 Plant Science
Topic 13 Plant Science
Subtopics 13.1.2, 13.1.3,
Subtopics 13.1.2, 13.1.3,
13.1.4
13.1.4
Objectives:
Objectives:
List and describe the major plant organs their
List and describe the major plant organs their
structure and function
structure and function
List and describe the major types of plant cells and
List and describe the major types of plant cells and
their functions
their functions
List and describe the major types of plant tissues,
List and describe the major types of plant tissues,
identify their locations and describe their functions.
identify their locations and describe their functions.
Identify and describe the external parts of a monocot
Identify and describe the external parts of a monocot
and eudicot plant.
and eudicot plant.
Identify and describe the distribution of tissues in the
Identify and describe the distribution of tissues in the
stem, root, and leaf of a monocot and eudicot plant.
stem, root, and leaf of a monocot and eudicot plant.
Identify, describe, and explain the changes that occur
Identify, describe, and explain the changes that occur
in a eudicot stem as it matures.
in a eudicot stem as it matures.
Explain the relationship between the distribution of
Explain the relationship between the distribution of
tissues in the leaf and the functions of these tissues.
tissues in the leaf and the functions of these tissues.
Major Plant Organs
Major Plant Organs
Flowering plants possess three kinds of
Flowering plants possess three kinds of
vegetative (non-reproductive) organs:
vegetative (non-reproductive) organs:
roots,
roots,
stems, and leaves
stems, and leaves
.
.
The flower is the
The flower is the
reproductive organ of the Angiosperms.
reproductive organ of the Angiosperms.
Shoots consist
of stems and
leaves.
Functions are
photosynthesis
, support and
transport
Roots
anchor
and absorb
water and
minerals and
provides
nutrients for
the shoot
and
can be an
area of
storage
Organ Functions
Organ Functions
The shoot system of a plant consists of the stems
The shoot system of a plant consists of the stems
and the leaves, as well as flowers
and the leaves, as well as flowers
.
.
Leaves
Leaves
are the main sites of photosynthesis in plants
are the main sites of photosynthesis in plants
.
.
Stems
Stems
hold and display the leaves to the sun and provide
hold and display the leaves to the sun and provide
connections for the transport of materials between roots
connections for the transport of materials between roots
and leaves
and leaves
.
.
It may also serves as an area of storage.
It may also serves as an area of storage.
A
A
node
node
is the point where a leaf attaches to a stem
is the point where a leaf attaches to a stem
.
.
Regions of stem between nodes are the internodes
Regions of stem between nodes are the internodes
.
.
Flowers are modified leaves structure which
Flowers are modified leaves structure which
support the microsporangia and megasporangia
support the microsporangia and megasporangia
gametophyte generations and are involved in plant
gametophyte generations and are involved in plant
sexual reproduction. Flowers are usually located
sexual reproduction. Flowers are usually located
apically or a the end of a stem.
apically or a the end of a stem.
The root system provides support, storage and
The root system provides support, storage and
nutrition
nutrition
.
.
Plant Cell Types (Support and
Plant Cell Types (Support and
Storage)
Storage)
Parenchyma cells
Parenchyma cells
are the most
are the most
numerous type of cell in young
numerous type of cell in young
plants.
plants.
Parenchyma cells usually have
Parenchyma cells usually have
thin walls and large central
thin walls and large central
vacuoles.
vacuoles.
The photosynthetic cells in leaves
The photosynthetic cells in leaves
are parenchyma cells filled with
are parenchyma cells filled with
chloroplasts. These cells are
chloroplasts. These cells are
called mesophyll cells.
called mesophyll cells.
Some parenchyma cells store
Some parenchyma cells store
lipids or starch (potatoes).
lipids or starch (potatoes).
Other parenchyma cells serve as
Other parenchyma cells serve as
“packing material” and play a vital
“packing material” and play a vital
role in supporting the stem
role in supporting the stem
especially in nonwoody stems.
especially in nonwoody stems.
Collenchyma cells
Collenchyma cells
are supporting
are supporting
cells that lay down primary cell
cells that lay down primary cell
walls that are thick in the corners.
walls that are thick in the corners.
Collenchyma cells provide support
Collenchyma cells provide support
to leaf petioles, nonwoody stems,
to leaf petioles, nonwoody stems,
and growing organs.
and growing organs.
These cell types compose the
These cell types compose the
cortex and pith tissues of the root
cortex and pith tissues of the root
and stems.
and stems.
Plant Cell Types (Support)
Plant Cell Types (Support)
Sclerenchyma
Sclerenchyma
cells are the
cells are the
main supporting cells of a
main supporting cells of a
plant. They have a thick
plant. They have a thick
secondary cell wall that
secondary cell wall that
contains a substance called
contains a substance called
lignin, a component of wood.
lignin, a component of wood.
Therefore they are found in
Therefore they are found in
woody plants.
woody plants.
There are two types of
There are two types of
sclerenchyma cells: elongated
sclerenchyma cells: elongated
fibers and variously shaped
fibers and variously shaped
sclereids
sclereids
.
.
Fibers often organize into
Fibers often organize into
bundles
bundles
.
.
(They are common
(They are common
components of xylem.)
components of xylem.)
Sclereids may pack together
Sclereids may pack together
very densely. (Sclereids are
very densely. (Sclereids are
found in fruits such as pears
found in fruits such as pears
and are what given them their
and are what given them their
gritty texture.) They are often
gritty texture.) They are often
referred to as “stone cells”.
referred to as “stone cells”.
Plant Cell Types Vascular (Transport)
Plant Cell Types Vascular (Transport)
Xylem
Xylem
The xylem conducts water from roots to above ground plant parts.
The xylem conducts water from roots to above ground plant parts.
It contains conducting cells called
It contains conducting cells called
tracheary elements
tracheary elements
.
.
Tracheids are evolutionarily more ancient tracheary elements
Tracheids are evolutionarily more ancient tracheary elements
found in gymnosperms.
found in gymnosperms.
Both tracheary elements and
Both tracheary elements and
tracheids
tracheids
undergo apoptosis(die)
undergo apoptosis(die)
and do their jobs as empty cells (only the cell walls remain).
and do their jobs as empty cells (only the cell walls remain).
Vessel elements
Vessel elements
are the water “pipeline” system in flowering
are the water “pipeline” system in flowering
plants, also formed from dead cells. Flowering plants have both
plants, also formed from dead cells. Flowering plants have both
tracheids and vessel elements.
tracheids and vessel elements.
Vessel elements are generally larger in diameter than tracheids
Vessel elements are generally larger in diameter than tracheids
and are laid down end-to-end to form hollow tubes.
and are laid down end-to-end to form hollow tubes.
Phloem
Phloem
Cells of the phloem are alive when they do their job, unlike those
Cells of the phloem are alive when they do their job, unlike those
of the xylem.
of the xylem.
The characteristic cell of the phloem is the
The characteristic cell of the phloem is the
sieve tube member
sieve tube member
.
.
Cells of the phloem are arranged end-to-end and form long sieve
Cells of the phloem are arranged end-to-end and form long sieve
tubes, which transport carbohydrates and other materials.
tubes, which transport carbohydrates and other materials.
The plasmodesmata in sieve tube members enlarge as they
The plasmodesmata in sieve tube members enlarge as they
mature, resulting in end walls that look like sieves.
mature, resulting in end walls that look like sieves.
At functional maturity, a sieve tube is filled with sieve tube sap
At functional maturity, a sieve tube is filled with sieve tube sap
(water, sugars, and other solutes).
(water, sugars, and other solutes).
The sieve tube members have adjacent companion cells.
The sieve tube members have adjacent companion cells.
Companion cells
Companion cells
retain all their organelles and may regulate the
retain all their organelles and may regulate the
performance of and support the sieve tube members.
performance of and support the sieve tube members.
Xylem and Phloem Cell
Xylem and Phloem Cell
Types
Types
Plant Tissues
Plant Tissues
A tissue is an organization of cells that work
A tissue is an organization of cells that work
together as a functional unit.
together as a functional unit.
Parenchyma cells make up parenchyma
Parenchyma cells make up parenchyma
tissue, which is a simple tissue.
tissue, which is a simple tissue.
Xylem and phloem are complex tissues; they
Xylem and phloem are complex tissues; they
are composed of a number of different cell
are composed of a number of different cell
types.
types.
Tissues are grouped into tissue systems that
Tissues are grouped into tissue systems that
extend throughout the body of the plant
extend throughout the body of the plant
from to form the various organs of the plant.
from to form the various organs of the plant.
There are three plant tissue systems:
There are three plant tissue systems:
vascular, dermal, and ground
vascular, dermal, and ground
.
.
Plant Tissues
Plant Tissues
Vascular Tissue
Vascular Tissue
The
The
vascular tissue system includes the
vascular tissue system includes the
xylem and phloem
xylem and phloem
; it is the conductive or
; it is the conductive or
“plumbing” system of the plant.
“plumbing” system of the plant.
The
The
phloem transports carbohydrates
phloem transports carbohydrates
from sites of production (sources such as
from sites of production (sources such as
leaves) to sites of utilization for energy or
leaves) to sites of utilization for energy or
where it is being stored (sinks) elsewhere
where it is being stored (sinks) elsewhere
in the plant.
in the plant.
The
The
xylem distributes water and mineral
xylem distributes water and mineral
ions taken up by the roots to the stem and
ions taken up by the roots to the stem and
leaves
leaves
.
.
Dermal Tissue
Dermal Tissue
The
The
dermal tissue system is the outer
dermal tissue system is the outer
covering of the plant
covering of the plant
.
.
All parts of the young plant body are
All parts of the young plant body are
covered by an
covered by an
epidermis, which is a single
epidermis, which is a single
layer or multiple layers of cells.
layer or multiple layers of cells.
The epidermis contains epidermal cells
The epidermis contains epidermal cells
and other specialized cells such as guard
and other specialized cells such as guard
cells.
cells.
The
The
shoot epidermis secretes a layer of
shoot epidermis secretes a layer of
wax-covered cutin, the cuticle, which helps
wax-covered cutin, the cuticle, which helps
retard water loss from stems and leaves.
retard water loss from stems and leaves.
Ground Tissue
Ground Tissue
The ground tissue system makes up
The ground tissue system makes up
the rest of a plant and consists
the rest of a plant and consists
primarily of parenchyma tissue.
primarily of parenchyma tissue.
Ground tissue functions primarily
Ground tissue functions primarily
in storage, support,
in storage, support,
photosynthesis, and the production
photosynthesis, and the production
of defensive and attractant
of defensive and attractant
substances (oils and toxins).
substances (oils and toxins).
Meristems (Plant Stem Cells)
Meristems (Plant Stem Cells)
In plants the growth of
In plants the growth of
roots and stems is indeterminate and is
roots and stems is indeterminate and is
generated from specific regions of active cell division.
generated from specific regions of active cell division.
The localized regions of cell division in plants, called
The localized regions of cell division in plants, called
meristems
meristems
, are
, are
forever embryonic.
forever embryonic.
They have the ability to produce new cells
They have the ability to produce new cells
indefinitely.
indefinitely.
The cells of meristematic tissues are analogous to the stems cells
The cells of meristematic tissues are analogous to the stems cells
found in animals
found in animals
.
.
When a meristem cell divides, one daughter cell develops into
When a meristem cell divides, one daughter cell develops into
another meristem cell, and the other differentiates into a more
another meristem cell, and the other differentiates into a more
specialized cell. The meristem gives rise to all plant cell and tissue
specialized cell. The meristem gives rise to all plant cell and tissue
types.
types.
There are two types of meristems:
There are two types of meristems:
Apical meristems give rise to the primary plant body, which is the
Apical meristems give rise to the primary plant body, which is the
entire body of many plants.
entire body of many plants.
Lateral meristems give rise to the secondary plant body.
Lateral meristems give rise to the secondary plant body.
The stems and roots of some plants form wood and become thick; it
The stems and roots of some plants form wood and become thick; it
is the lateral meristems that give rise to the tissues responsible for
is the lateral meristems that give rise to the tissues responsible for
this thickening.
this thickening.
Apical meristems are located at the tips of roots and stems and in
Apical meristems are located at the tips of roots and stems and in
buds.
buds.
Shoot apical meristems supply the cells that extend stems and
Shoot apical meristems supply the cells that extend stems and
branches.
branches.
Root apical meristems supply the cells that extend roots.
Root apical meristems supply the cells that extend roots.
Apical meristems are responsible for primary growth, which leads to
Apical meristems are responsible for primary growth, which leads to
elongation and organ formation.
elongation and organ formation.
Location of Meristematic
Location of Meristematic
Tissues
Tissues
Secondary Growth
Secondary Growth
Some roots and stems develop a secondary body
Some roots and stems develop a secondary body
(wood and bark).
(wood and bark).
Secondary body tissues are derived from two lateral
Secondary body tissues are derived from two lateral
meristems: vascular cambium and cork cambium.
meristems: vascular cambium and cork cambium.
Vascular cambium
Vascular cambium
is a cylindrical tissue consisting
is a cylindrical tissue consisting
of cells that divide frequently.
of cells that divide frequently.
These cells form the
These cells form the
secondary xylem toward the inside, and the
secondary xylem toward the inside, and the
secondary phloem towards the outside of the stem.
secondary phloem towards the outside of the stem.
The
The
cork cambium
cork cambium
produces protective cells that
produces protective cells that
protect the outermost layers of the stem from water
protect the outermost layers of the stem from water
loss and microorganisms.
loss and microorganisms.
The layer of growth of the cork cambium is the
The layer of growth of the cork cambium is the
periderm
periderm
.
.
Growth in the diameter of the stems and roots,
Growth in the diameter of the stems and roots,
produced by vascular and cork cambia, is called
produced by vascular and cork cambia, is called
secondary growth
secondary growth
.
.
Wood is secondary xylem
Wood is secondary xylem
.
.
Bark is everything external to the vascular cambium
Bark is everything external to the vascular cambium
(periderm plus secondary phloem)
(periderm plus secondary phloem)
.
.
Young Stem Structure (Monocot and
Young Stem Structure (Monocot and
Eudicots)
Eudicots)
The shoot apical
The shoot apical
meristem also forms the
meristem also forms the
three primary meristems:
three primary meristems:
protoderm, ground
protoderm, ground
meristem, and cambium
meristem, and cambium
.
.
It also lays down the
It also lays down the
beginnings of leaves and
beginnings of leaves and
lateral buds, called
lateral buds, called
leaf
leaf
primordia and bud
primordia and bud
primordia.
primordia.
Vascular tissue in the
Vascular tissue in the
stem is arranged in
stem is arranged in
vascular bundles.
vascular bundles.
The eudicot stem also
The eudicot stem also
contains pith and cortex
contains pith and cortex
storage tissues. Only
storage tissues. Only
eudicot stems have a
eudicot stems have a
vascular cambium or
vascular cambium or
cork cambium!
cork cambium!
Growing Eudicot Stem
Growing Eudicot Stem
Structure
Structure
These
tissues form
a vascular
bundle. In
woody plants
they grow
together and
fuse to form a
continuous ring
creating annual
growth rings.
Mature Eudicot Stem
Mature Eudicot Stem
Secondary growth increases the
Secondary growth increases the
diameter of stems and roots.
diameter of stems and roots.
Secondary growth results from
Secondary growth results from
the activity of vascular and cork
the activity of vascular and cork
cambia.
cambia.
Vascular rays connect storage
Vascular rays connect storage
parenchyma to the sieve tubes of
parenchyma to the sieve tubes of
the phloem.
the phloem.
Only eudicots have a vascular
Only eudicots have a vascular
cambium and a cork cambium and
cambium and a cork cambium and
thus undergo secondary growth
thus undergo secondary growth
.
.
Cross sections of most tree trunks
Cross sections of most tree trunks
in temperate zone forests have
in temperate zone forests have
annual rings
annual rings
.
.
Annual rings form due to
Annual rings form due to
differential rates of growth in
differential rates of growth in
spring (when water is plentiful)
spring (when water is plentiful)
and in summer
and in summer
.
.
Wood that is no longer conducting
Wood that is no longer conducting
water is known as heartwood
water is known as heartwood
.
.
Sapwood is wood that is actively
Sapwood is wood that is actively
conducting water and minerals in
conducting water and minerals in
the tree.
the tree.
Roots
Roots
The root apical meristem produces all the cells that contribute to growth in
The root apical meristem produces all the cells that contribute to growth in
the length of the root.
the length of the root.
The root cap covers and protects the delicate growing area of the root as it
The root cap covers and protects the delicate growing area of the root as it
pushes through the soil.
pushes through the soil.
The root cap also detects the pull of gravity and controls the downward
The root cap also detects the pull of gravity and controls the downward
growth of roots.
growth of roots.
Tissues of the root are divided into three zones: cell division, cell elongation,
Tissues of the root are divided into three zones: cell division, cell elongation,
and cell differentiation.
and cell differentiation.
The growing region above the apical meristem comprises the three
The growing region above the apical meristem comprises the three
cylindrical meristems: protoderm, ground meristem, and procambium.
cylindrical meristems: protoderm, ground meristem, and procambium.
The protoderm gives rise to the epidermis, adapted for protection and
The protoderm gives rise to the epidermis, adapted for protection and
absorption of water and minerals. Root hairs are long, flattened epidermal
absorption of water and minerals. Root hairs are long, flattened epidermal
cells that increase the root’s surface area and aid in water absorption.
cells that increase the root’s surface area and aid in water absorption.
The ground meristem gives rise to the cortex, which functions in storage.
The ground meristem gives rise to the cortex, which functions in storage.
The endodermis , which surrounds the central portion of the root called the
The endodermis , which surrounds the central portion of the root called the
vascular cylinder or stele, contains suberin, which makes the cells waterproof
vascular cylinder or stele, contains suberin, which makes the cells waterproof
and enables control of water into the vascular tissue.
and enables control of water into the vascular tissue.
The stele is produced by the procambium, and includes xylem, phloem, and
The stele is produced by the procambium, and includes xylem, phloem, and
pericycle tissues.
pericycle tissues.
The pericycle consists of one or more layers of undifferentiated cells and has
The pericycle consists of one or more layers of undifferentiated cells and has
three important functions.
three important functions.
It is the tissue in which lateral roots arise.
It is the tissue in which lateral roots arise.
It can contribute to secondary growth by giving rise to a lateral meristem
It can contribute to secondary growth by giving rise to a lateral meristem
that thickens the root.
that thickens the root.
Its cells contain membrane transport proteins that export nutrient ions
Its cells contain membrane transport proteins that export nutrient ions
into the cells of the xylem.
into the cells of the xylem.
Root Tip Structure
Root Tip Structure
Root Structure (Monocot vs Eudicot)
Root Structure (Monocot vs Eudicot)
Root Structure (Monocot vs
Root Structure (Monocot vs
Eudicot)
Eudicot)
Eudicots have their Monocots
have pith
xylem centrally located tissue that is
centrally
usually in an X formation. located.
Xylem cells
no pith is present! arranged in
a ring.
Leaf Structure
Leaf Structure
Leaf anatomy is adapted to carry out photosynthesis,
Leaf anatomy is adapted to carry out photosynthesis,
limit evaporative water loss, and transport the
limit evaporative water loss, and transport the
products of photosynthesis to the rest of the plant.
products of photosynthesis to the rest of the plant.
The two zones in leaf parenchyma that
The two zones in leaf parenchyma that
photosynthesize are the palisade mesophyll and the
photosynthesize are the palisade mesophyll and the
spongy mesophyll.
spongy mesophyll.
Within the mesophyll is air space through which CO
Within the mesophyll is air space through which CO
2
2
can diffuse to the photosynthesizing cells
can diffuse to the photosynthesizing cells
.
.
Veins supply mesophyll cells with water and
Veins supply mesophyll cells with water and
minerals, and they transport the products of
minerals, and they transport the products of
photosynthesis to the rest of the plant.
photosynthesis to the rest of the plant.
The epidermis of the leaf is the outermost cell layer,
The epidermis of the leaf is the outermost cell layer,
which is covered by a waxy cuticle. The epidermis
which is covered by a waxy cuticle. The epidermis
functions to keep water and photosynthetic products
functions to keep water and photosynthetic products
in the leaf.
in the leaf.
Guard cells allow controlled gas exchange through
Guard cells allow controlled gas exchange through
pores in the leaf (the stomata).
pores in the leaf (the stomata).
Leaf Structure
Leaf Structure
Leaf Structure
Leaf Structure