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Flowering Plants: Structure
and Organization
10.1 Organs of Flowering Plants
10.2 Tissues of Flowering Plants
10.3 Organization and Diversity of Roots
10.4 Organization and Diversity of Stems
10.5 Organization and Diversity of Leaves
Flowering Plants: Structure
and Organization
• Over 80% of all living plants are flowering plants
(angiosperms).
• The organization of flowering plants allows them
to grow on land.
• The vegetative organs of a flowering plant
consist of root, stems, and leaves.
• The leaves shape facilitates absorption of solar
energy and CO2.
• Roots anchor the plant and also absorb water
and minerals.
• Strong stems conduct water up to the leaves
from the roots
10.1 Organs of Flowering
Plants
Terminal bud
• A plants possess two systems:
1. The root system (roots).
2. The shoot system (stem and
leaves).
Leaf
Blade
Vein
Petiole
Axillary bud
Stem
Node
• A typical plant have three vegetative
organs which concerned with the
growth and nutrition: (root, stem
and leaves).
Internode
Node
Shoot system
Root system
• Also, a typical plant have
reproductive organs which have
specific function (reproduction):
Flowers, seeds, and fruits
Root
branch
Root
hairs
1- Roots system (The Root)
• Roots (in the majority of plants) is located underground.
• As a rule, the root system is extent to the shoot system.
Function of the roots
• Anchors the plant in the soil
• Gives it’s support
• Absorbs water and minerals from the soil for the entire plant
• Roots produce hormones that stimulate the growth of stems
• Store the foods, (as in Carrots, sweet and potatoes)
Suitability of the roots to their function
• The cylindrical shape to penetrate the soil and to absorb water
from all sides
• Root hairs and branches: increase the absorptive capacity
• Numerous root hairs increase the absorptive surface of a root
The shoot system : 1- The stem
• The shoot system of a plant is composed of the stem,
branches and leaves.
• Stem is the main axis of a plant
• Terminal bud occur at the top of the stem that allows
the stem to elongate and produce new leaves.
• An axillary bud, located at a node in the upper angle
between the leaf and the stem
• Axillary bud can produce new branches of the stem (or
flowers).
• A node occurs where leaves are attached to the stem.
• The region between nodes is called an internode.
Branch
Stem
Leaf
2- Leaves
Leaves are the major part
of a plant that carries on photosynthesis
• Photosynthesis is a process that requires water, carbon
dioxide, and sunlight.
• The size, shape, color, and texture of leaves are highly
variable.
• The shape of leaves can vary from spines to deeply
lobed.
• Plants that bear leaves the entire year are called
evergreens and those that lose their leaves every year
are called deciduous.
• The wide portion of the leaf is called the blade.
• The petiole is a stalk that attaches the blade to the
stem.
• The upper acute angle between the petiole and stem is
the leaf axil where the axillary bud is found.
• Not all leaves are foliage leaves.
• Some are specialized to protect buds, attach to objects
(tendrils), store food (bulbs), or even capture insects.
Monocotyledons and Eudicotyledons
• Flowering plants are divided into two groups, depending on the
number of cotyledons, or seed leaves, in the embryonic plant.
a. Monocotyledons (Monocots): have one cotyledon.
b. Eudicotyledons (Eeudicots): have two cotyledons.
1. Cotyledons of eudicots supply nutrients for seedlings, but in
monocots acts as a transfer tissue and the nutrients are derived
from the endosperm .
2. In the monocot root vascular tissues occurs in a ring.
3. In the eudicot root, the xylem is star-shaped and the phloem is
located between the points of the star.
4. Leaf veins are vascular bundles within a leaf.
5. Leaf veins in Monocots exhibit parallel venation, but in eudicots
exhibit netted venation, which may be either pinnate or palmate.
6. Monocots have their flower parts arranged in multiples of three,
and eudicots have their flower parts arranged in multiples of four
or five.
Root
Stem
Leaf
Flower
Monocot
Seed
Xylem and phloem in ring
Two cotyledon in seed
Phloem between
arms of xylem
Vascular bundles
in a distinct ring
Leaf veins parallel
Leaf veins in net
Flower parts 3
or multiple
Dicot
One cotyledon in seed
Vascular bundles
scattered in stem
Flower parts 4 or 5
or multiple
10.2 Tissues of Flowering
Plants
• A flowering plant has the ability to grow because it possesses
meristematic (embryonic) tissue.
• Apical meristems are located at or near the tips of stems and
roots.
• Apical meristems increase the length of the plants.
• Apical meristem continually produces three types of
meristem:
1.Protoderm which gives rise to epidermis (forms the outer
protective covering of a plant)
2.Ground meristem produces ground tissue (fills the interior
of a plant)
3.Procambium produces vascular tissue (transports water and
nutrients in a plant and provides support.
Epidermal Tissue
• The entire body of both non-woody (herbaceous) and young
woody plants is covered by a layer of epidermis.
• The walls of epidermal cells that are exposed to air are covered
with a waxy cuticle for prevent water loss and protects the plants
against bacteria and other organisms that might cause disease.
• In roots, certain epidermal cells have long, slender projections
called root hairs, to increase the surface area of the root for
absorption of water and minerals; they also help anchor the plant
firmly in place.
• On stems, leaves, and reproductive organs, epidermal cells
produce hairs called trichomes.
• In leaves, the lower epidermis of eudicots and both surfaces of
monocots contain specialized cells called guard cells (epidermal
cells) with chloroplasts.
Ground Tissue
• Ground tissue forms the bulk of a flowering plant and contains
parenchyma, collenchyma, and sclerenchyma cells
• Parenchyma
• Parenchyma cells are the
most abundant tissues in
the plant organs.
• They may contain
chloroplasts and carry on
photosynthesis
• Collenchyma
• Collenchyma cells are like
parenchyma cells except they
have thicker primary walls.
• The thickness is uneven and
usually involves the corners
of the cell.
• Collenchyma cells give
flexible support to immature
regions of a plant body.
Sclerenchyma
fiber
• Sclerenchyma cells have thick
secondary cell walls of lignin, that
makes the walls tough and hard.
• Most sclerenchyma cells are nonliving
• Their primary function is to support
the mature regions of a plant.
• Two types of sclerenchyma cells are
fibers and sclereids.
• Although fibers are occasionally found
in ground tissue, most are in vascular
tissue.
• Fibers are sometimes commercially
important.
• Sclereids are shorter than fibers and
are found in seed coats and nutshells.
• The hardness of nuts and peach pits is
due to sclereids.
sclereids
Vascular Tissue
• There are two types of vascular (transport) tissue:
• Xylem transports water and minerals from the roots to the leaves.
• phloem transports sucrose and other organic compounds,
including hormones, usually from the leaves to the roots.
• Both xylem and phloem are considered complex tissues because
they are composed of two or more kinds of cells.
• Xylem
• Xylem contains two types of conducting cells:
• Tracheids and vessel elements (VE), which are modified
sclerenchyma cells. Both cells are hollow and nonliving.
• But the vessel elements are larger, may have perforation plates in
their end walls, and are arranged to form a continuous vessel for
water and mineral transport.
vessel
element
vessel
element
tracheids
xylem
parenchyma
a. Xylem micrograph (left) and drawing (to side)
perforation
plate
tracheids
Pitted
walls
pits
b. Two types of vessels
Xylem structure
a. Photomicrograph of xylem vascular tissue and drawing showing general organization of xylem tissue.
b. Drawing of two types of vessels (composed of vessel
elements)—the perforation plates differ. c. Drawing of tracheids.
c. Tracheids
Phloem:
• The conducting cells of phloem are specialized parenchyma cells
called sieve-tube members which arranged to form a continuous
sieve tube.
• Sieve-tube members contain cytoplasm but no nuclei.
• Each sieve-tube member has a companion cell, which does have a
nucleus.
• The companion cells are believed to be involved in the transport
function of phloem.
• Sclerenchyma fibers also lend support to phloem.
In the roots, the vascular tissue is located in the vascular cylinder;
In the stem, it forms vascular bundles;
In the leaves, it is found in leaf veins.
sieve plate
sieve-tube
member
sieve-tube
member
companion cell
companion
cell
sieve plate
nucleus
phloem
parenchyma
a. Phloem micrograph (left) and drawing (to side)
b. Sieve-tube member and companion cells
Phloem structure
a. Photomicrograph of phloem vascular tissue and drawing showing general organization of phloem tissue. b. Drawing of sieve tube
(composed of sieve-tube members) and companion cells