Transcript Division: Cycadophyta - Welcome to Mt. San Antonio College

Cycads are vascular,
seed plants that are
palm-like and are called
Sago Palms. The leaves
are found in a cluster at
the tops of the trunks.
Cycads were first to show
true secondary growth
along plant’s evolutionary
history.
Division:
Cycadophyta
Be able to recognize the
example.
1
The Ginkgo or
Maidenhair Tree have
characteristic fan-like
leaves. There is only one
species (from China) that
has survived. Only males
are usually planted in
yards because the female
plants have messy and
foul smelling fruit.
Be able to recognize the
example in the jar.
Division:
Ginkgophyta
2
The Gnetophytes are
unique gymnosperms
because they have
vessel elements. Our
example is Ephedra
or Mormon Tea. It
produces a drug
called ephedrine
which raises the heart
rate and raises blood
pressure.
Be able to recognize
the example.
Division:
Gnetophyta
3
The Conifers, which
include pines,
spruces, hemlocks,
and firs, are woody
trees or shrubs. Most
conifers have leaves
(megaphylls) that are
modified into needles
or scales.
Division:
Coniferophyta
Be able to recognize
the example.
4
The Pine Tree
contains both
male and female
cones. The pollen
(staminate) cones
are found low in
the tree and
produce pollen.
The ovulate cones
are high in the tree
and produce
seeds.
Division:
Coniferophyta
5
The male
(staminate) cone
consists of protective
scales called
(microsporophylls)
that contain
microsporangia
which go through
meiosis to produce
four haploid
microspores. These
microspores will
develop into pollen.
Male Cones
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Pollen Grains
The microspores
develop into pollen
grains. Each pollen
grain consists of four
cells and a pair of
wings which are
used for dispersal.
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Pollen Grains with Pollen Tube
Microsporangia produce
pollen grains with 4 cells:
2 prothallial cells, 1
generative cell (which
becomes a sterile cell
and a spermatogenous
cell) and one tube cell.
The spermatogenous cell
produces 2 sperm. Be
able to recognize the
pollen grain, wings,
pollen tube, and sperm.
8
The female (ovulate) cone
consists of protective
scales called
(megasporophylls) that
contain megasporangia
(ovules). The megaspore
mother cells produce 4
megaspores through the
process of meiosis. The
megaspores are
surrounded by a nutritional
nucellus and a protective
seed coat called an
integument. The
megaspores develop into a
female gametophyte.
Female Cones
9
At the end of the female
gametophyte (n), an
archegonium (n) which
contains two eggs (n) that
develop. They are
surrounded by two layers
of tissue, the nucellus (2n)
and the integument (2n).
The integument has a
channel that allow sperm in
(a micropyle) and the two
layers are separted by a
pollen chamber.
Female
Gametophyte
10
The pine embryo consist of
an integument, an
endosperm (food source),
cotyledons (food source),
the hypocotyl (that
develops into the shoot
system), and the radicle
(which develops into the
root system). While
developing, one of the
layers of the integument
will become a seed coat for
the seed.
Female Cone
with Mature
Embryo
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Angiosperm
Be able to recognize
the parts of a flower
and know their
functions
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Ovary Position
When the ovary is embedded below the calyx
and corolla, it is called epigynous. When the
ovary is produced on top of they parts, it is
called hypogynous. When the ovary is centrally
positioned it is called perigynous. Be able to
recognize these positions on the drawing.
13
Placentation
The position of the ovary where the ovules
(seeds) attach is called placentation. There are
three types of arrangements: parietal (top),
axial (middle), and free central (bottom).
pigynous. Be able to recognize these positions
on the drawing.
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Male
Gametophyte
The male gametophyte in flowering plants is a
pollen grain. They are produced in anthers. The
anthers have fours chambers that produce
quartets of pollen. The quartets break into
individual pollen grains.
15
Fertilization
The majority of plants do not self-fertilize
themselves. They depend on cross fertilization:
the transfer of pollen from one individual plant
to another. The most common mechanism to
keep plants from fertilizing themselves is called
are produced in self-incompatibility. This works
similar to an animal’s immune system where a
biochemical block prevents the pollen from
completing its development.
16
Germinating Pollen
Under suitable
conditions, the tube
cell grows into a
pollen tube (with a
tube nucleus) inside
the style of another
flower. As the tube
grows, the
generative nucleus
lags behind and
eventually produces
two sperm.
17
Female
Gametophyte
In the female
gametophyte, the
ovule (surrounded by
the ovary wall)
develops an embryo
sac which goes
through the process
of meiosis to create
a megaspore. The
megaspore than
goes through mitosis
twice to produce the
four-nucleate stage.
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Female
Gametophyte
The 8-nucleate stage ovary.
The emryo is located within
the embryo sac which
contains 3 antipodals (which
disappear after fertilization), 2
polar nuclei (which join with a
sperm that produces the
endosperm (3n), 2 synergids
(which disappear), and an
egg (which is fertilized).
Because a sperm joins an
egg and another fuses with
the polar nuceli in flowering
plants, it is called double
fertilization.
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Seeds
Be able to
recognize the
parts labeled in
the diagram to
the right.
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Fruit and Seed
Dispersal
Dispersal by Wind:
Many fruits have a wing to
allow for dispersal and
may be carried up to six
miles away. Fruits that
are too large may even be
rolled along the ground
due to the wind. Seeds
themselves may be
winged or small enough to
be moved by a slight
breeze.
21
Fruit and Seed
Dispersal
Dispersal by Animal:
Birds, mammals and ants
all act as dispersal agents.
These seed or fruits can
be carried and dropped,
collected and stored,
eaten and passed through
a digestive tract, or stuck
in a mammals’s fur or a
bird’s feather’s. Humans
are the most efficient
transporters of fruits and
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seeds.
Fruit Wall
The fruit wall is a mature
ovary. The skin forms the
exocarp while the inner
boundary around the
seed(s) forms the
endocarp. The are
between these two areas
is called the mesocarp.
The three regions
collectively are called the
pericarp. In dry fruits, the
pericarp is often very thin.
23
Roots
Roots are used
to anchor the
plant in the soil,
to absorb
minerals and
water, conduct
minerals and
water and store
food.
24
Root Tip Regions
Regions
Function
Root Cap
Protect the apical meristem
Perception of Gravity
Cell Division
Production of new cells
Pushes meristem and root cap
through ground
Development of protoderm,
procambium, ground tissue
Apical Meristem
Elongation
Maturation
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Monocot Root
Tissue
Origin
Function
Epidermis
Protoderm
Produce root hairs,
protection, absorption
Stele
Procambium
Cortex
Ground Meristem
Xylem: water movement
Phloem: food movement
Pericycle: lateral roots
Cortex: storage
Endodermis: regulation of
movement
Passage Cells: lateral
movement of water
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Monocot Root
The three primary
meristems give rise to the
three primary tissues of
roots. (protoderm,
procambium, and the
ground meristem). You
will be beld responsible
for the following tissues:
Epidermis, Stele, Xylem,
Phloem, Pericycle, Cortex,
Endodermis, and Passage
Cells. You also need to
know their functions.
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Dicot Root
A dicot root differs from a
monocot root because it
usually lacks a pith. The
three primary meristems
give rise to the three
primary tissues of roots.
(protoderm, procambium,
and the ground meristem).
You will be beld
responsible for the
following tissues:
Epidermis, Stele, Xylem,
Phloem, Pericycle, Cortex,
Endodermis, and Passage
Cells. You also need to
know their functions.
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Dicot Root
Tissue
Origin
Function
Epidermis
Protoderm
Produce root hairs,
protection, absorption
Stele
Procambium
Cortex
Ground Meristem
Xylem: water movement
Phloem: food movement
Pericycle: lateral roots
Cortex: storage
Endodermis: regulation of
movement
Passage Cells: lateral
movement of water
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Carrot
A carrot is a modified
taproot. Look at a
longitudinal and cross
section of a carrot
(Daucus) root and be able
to identigy the following
structures: Cortex, stele,
pericycle and lateral roots.
The cortex and stele are
separated by a white line
called pericycle. Small
white lines can be seen
going from the pericycle to
the outside. These are
the lateral roots.
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As the root of a young seedling
grows, it penetrates the soil.
Epidermal cells produce root They
absorb water and dissolved
minerals from the soil. The small
size and larger number of hairs
enormously increase the
absorptive surface of the root and
bring it in contact with a large
volume of soil. For optimum
growth, the soil should be loosely
packed in order to allow for gas
exchange. Observe the living
radish seedlings (Rhaphanus)
under a dissecting scope. The
white strings along the roots are
the root hairs.
Root Hairs
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Vascular tissue running
the length of a stem
composed of primary
tissue is called a
vascular bundle.
Vascular bundles are
made up of xylem
(usually seen in red)
which face the pith and
phloem (usually seen in
green) which faces the
cortex. Be able to
recognize the difference
between the two tissues.
Vascular
Bundles
32
In stems of herbaceous
plants, there is usually only
primary tissue. Identify the
following structures: vascular
bundles, pith, epidermis,
fibers, phloem, and xylem.
Notice that the vascular
tissue is found in vascular
bundles arranged in a ring.
usually seen in red) Inside
the ring is a collection of
ground tissue called the pith.
The fibers stain red and they
are found on the outer tips of
the vascular bundles. The
fibers add support.
Herbaceous
Dicot Stem
(Ranunculus)
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The tissue arrangement in
monocot stems differ from
that of dicots. The vascular
bundles are scattered and
not found in any set pattern.
The xylem is usually found
toward the center of the stem
and the phloem is usually
facing outward within a
vascular bundle. Look at the
prepared slide of a scross
section (CS) of the
herbaceous monocot Zea
(corn). The monocot stem
does not have a true pith.
Herbaceous
Monocot Stem
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Woody Dicot Stem
Most vascular plants undergo secondary
growth, which increases girth (width). Two
lateral meristems are responsible for secondary
growth: the vascular cambium which produces
xylem and pholem: and the cork cambium
which produces a tough covering called bark.
Secondary growth occurs in all gymnosperms
and most dicot species of angiosperms but is
rare in monocots. We will observe prepared
slides of the tree basswood (Tilia) to
demonstrate the different tissues moving from
the inside to the outside of the stem.
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Woody
Dicot
Stem
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Woody Dicot Stem
Tissue
Function
Pith
Storage
Primary Xylem
Moves water and minerals
upward
Secondary Xylem Moves water and minerals
upward
Vascular Cambium Produces secondary growth
Secondary Phloem Moves nutrients around the
plant
Primary Phloem
Moves nutrients around the
plant
37
Woody Dicot Stem
(Continued)
Tissue
Function
Cortex
Storage
Phelloderm
Made of parenchyma cells
Unknown function
Produces phelloderm and cork
cells
Physical barrier for protection
Cork Cambium
Cork Cells
38
Age of a Woody Dicot
The age of a dicot
can be determined
by counting the
number of rings.
The rings are made
up of dead cells
called xylem. The
type of year (rainfall
amounts) can be
determined by the
width of the ring.
39
Tissues of a
Tree Trunk
By examining a cross
section of a mature tree,
many important regions
can be seen by the
unaided eye. Sapwood
and heartwood are
made up of secondary
xylem. Sapwood is
younger and function for
water movement.
Heartwood is older,
darker wood that no
longer functions for
water movement and is
used for support.
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Spiral Xylem
Vessels
Conifers have xylem that
consist primarily of tracheids;
no fibers or vessel elements.
The wood tends to be soft and
is often called soft woods. The
woods of woody dicots
possess vessels elements and
tend to be hard and are called
hard woods. Xylem vessels in
woody dicots are spiral in
shape. These special cells are
used for carrying water and
minerals upward in the stem.
Be able to recognize a spiral
xylem vessel from the melon
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plant Cucurbita.
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The Leaf
Leaves are the photosynthetic organs of the
plant. Leaves act as solar panels that capture
sunlight and convert solar energy into chemical
energy in the form of sugars using carbons
dioxide and water. The structure of a leaf can
actually be divided into three major regions: the
epidermis, the mesophyll, and the veins (vascular
bundles). Observe the cross section (CS) of a
leaf. You will be held responsible for the following
regions, structures and functions.
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The Leaf
Region
Structure
Function
Epidermis
Cuticle
Prevents water loss
Epidermal
Cells
Guard Cells
and Stomates
Pallisade
Layer
Spongy Layer
Protective layer
Mesophyll
Veins
Vascular
Bundles
Gas Exchange
Photosynthesis
Photosynthesis and gas
exchange
Transport
44
The Lower
Epidermis
Look at the prepared slide of
the lower epidermis (Sedum –
CS) Be able to recognize the
following structures: Guard
cells, stomates, lower
epidermal cells. The epidermal
cells will look like puzzle
pieces. The guard cells are
regulated by turgor pressure.
When they are full, the
stomates are open. When they
are empty, the stomates are
closed.
45
Pine Needles
Pine trees have adaptations
for living in arid conditions.
In arid regions, one of the
largest problems faced by
plants is water loss through
the stomates. Pine needles
have their stomates
recessed (sunken) within the
surface of the leaf. Observe
a cross section (CS) of a
pine needle and be able
tecognize the following
structures: guard cells and
stomata.
46
Minerals and Plant
Nutrition
Plants need certain nutrients to do well. Know the
following symptoms and their causes.
Chlorosis – lack of N or K
Deep Green or Purple Pigmentation – lack of P or N
Stunted Growth – lack of P or N
Necrosis – Lack of K
47
Pitcher Plants
Pitcher plants are found in
damp, boggy soils in
northeast Florida, which are
deficient in nitrates and
phosphates. They capture
their prey by having their
funnel shaped leaves
covered with nectar glands
and down curved teeth.
Once the insect lands, they
move down to a slick area
with no foothold. The insect
falls into the fluid at the
bottom where it is absorbed.
48
Venus Flytrap
Venus Flytraps are found
in damp, boggy soils in the
Carolinas, which are
deficient in nitrate. They
capture their prey by using
their modified leaves that
contain two lobes. Each
lobe has an outer area that
contains teeth. Each lobe
has trigger hairs that
signal the leaves to close
on their prey (flies or larger
insects – smaller insects
can escape).
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Sundew
Sundews are found in
acid, boggy soils, along
roadside ditches, which
are deficient in nitrates.
They capture their prey by
having modified leaves
that contain stalked glands
or tentacles which contain
highly viscid mucus. They
catch only small or very
weak prey. Flies and ants
can escape.
50
Gibberellins
Gibberellic Acid effects germination.
Observe the seeds that were treated with
the hormone and compare them to the
control seeds. Gibberellic acids promote
seed germination and plants treated with it
will grow quicker. This hormone could be
used to speed up growth in agricultural
plants.
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Gibberellins
Gibberellic Acid effects growth rate.
Observe the plants that were treated with
the hormone and compare them to the
control plants. Gibberellic acids promote
stem elongation and plants treated with it
will grow longer. This hormone is used to
produce flower shoots but can cause
problems if the stems grow too quickly.
52
Some researchers believe
it is the tip of the plant.
Observe the plant that was
placed next to a light. Auxin
is the hormone that is
thought to be responsible
for the plant bending
toward the light. It is the
stem that is actually
“bending”. The plant
actually doesn’t bend. The
cells away from the light
are affected more by auxin
and elongate faster which
“bends” the plant toward
the light.
Phototropism
53
Shoots display a negative
gravitropism. Observe the
plant that was placed on its
side. Plants may tell up from
down by the settling of
Statoliths (plastids with
heavy starch grains). Auxin
is the hormone that is
though to be responsible for
the plant “bending” upward.
The stem actually doesn’t
bend. The cells on the
bottom of the plant are more
affected than the upper cells
and elongate faster which
“bends” the plant upward.
Gravitropism
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