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