Transcript vascular tissue

Plant
Anatomy
Plant bodies organized
into …
Root system
Embedded in soil
Anchor plant
Absorb H2O & nutrients
Store surplus sugars
Transport H2O, minerals, sugars &
hormones
Interact with soil fungi and
microorganisms that
provide nutrients
Shoot System
Leaves, buds, flowers, stems & fruit
 Functions:
– Photosynthesis
– Transport
– Reproduction
– Hormone synthesis
Undifferentiated plant tissue which
gives rise to new cells (growth). This
can differentiate into any other type
of tissue needed by the plant.
• at tips of branches & roots:
– growth = primary growth,
increases height
– apical meristem
• around the perimeter of
roots & stems:
– growth = secondary, increases
diameter
– lateral meristem
– In stems in can produce wood,
cork(bark) also occurs in roots.
Primary Growth:
Primary growth
occurs where
apical meristem,
is located….
tips of shoots
roots at “Zone
of cell division”.
Tip of Shoot
Zone of
cell
Division
Root Cap
Shoot
Root
Secondary Growth:
Lateral Meristem is
also known as the
VASCULAR CAMBIUM.
It develops into the
secondary xylem
and phloem, which
Increases the width of
the plant root or stem.
Plants have 3 Types of Mature
Tissue:
Epidermis
 – single cell thickness –
 protection – cuticle
Ground storage,
 photosynthesis and
secretion
Vascular–
 – Xylem – H2O, minerals
 – Phloem – carbs (sucrose)
= food
#1 -Epidermis –
The outermost layer of the plant covering leaves,
floral parts, fruits, seeds, stems and roots.
a. Generally one cell layer thick
b. Composed of parenchyma and/or sclerenchyma.
c. Often contain various types of hairs
d. Contains guard cells- form stomata for gas exchange
FUNCTIONS OF EPIDERMIS:
• Protect the underlying cells,
• Prevents loss of moisture by secreting the cuticle.
• Transparent epidermal cells allow sunlight
to pass through to the chloroplasts
• Stomata openings allow gas exchange, necessary
for photosynthesis and respiration,
• Water vapor will be lost through stomata during
transpiration.
• Root-hair epidermis provides more surface area for
absorption of water.
#2 -GROUND TISSUE
Ground Tissue forms most of the bulk of a plant.
Ground Tissue is composed of three cell types :
 sclerenchyma
 parenchyma
 collenchyma
• Parenchyma are the least specialized. They have thin
walls. Form numerous plastids including chloroplasts, & store
food. Cells can revert to meristem in response to injury.
• Collenchyma are elongated cells with thick walls.
They provide flexible support especially to new growth areas.
• Sclerenchyma have very thick walls and are dead at
maturity. They give flexible support, May be short ( nut
shells), long ( flax) or gritty ( pear fruits)
#3 - VASCULAR TISSUE:
• Vascular tissue consists of xylem and phloem.
These two types of vessels run side-by-side, extending
from roots to leaves. They provide channels for the
transport of water and nutrients.
Xylem- Conducts water and
minerals from the roots to the leaves.
• Composed of ground cells and 2
types of conducting cells:
– Tracheids (A)
• thin cells w/ slanted endsstacked atop each other. Pits
allow transfer between cells
– Vessel elements (B)
• Perforated end walls. Vessel
members join together into long
tubes called vessels. Occur
primarily in angiosperms
A
B
Phloem
• Carries dissolved “stuff”
synthesized by the plant
• Phloem composed of 2 types of
cells
– sieve –tube elements (A)
• Possess no nucleus,
mitochondrion, or chloroplast
• Rate of flow through sieve-tube
elements is high
B
– Companion cells (B)
• Adjacent companion cells –
Parenchyma cells that do enough
biochemistry to keep the sievetube elements and themselves
alive.
A
Transport of food.
The xylem sap is
always a very dilute
solution, but the
phloem sap may
contain up to 25%
of dissolved solids
such as sucrose and
amino acids.
Tissue System
and Its
Functions
Component
Tissues
Dermal Tissue
System
• protection
• prevention of
water loss
Epidermis
Periderm (in
older stems and
roots)
Ground Tissue
System
• photosynthesis
• food storage
• regeneration
• support
• protection
Parenchyma
tissue
Collenchyma
tissue
Sclerenchyma
tissue
Vascular Tissue
System
• transport of
water, minerals
• transport of food
Xylem tissue
Phloem tissue
Location of Tissue
Systems
Plant Organs:
•Roots
•Stems
•Leaves
Root Functions:
• Absorb Nutrients
• Anchor the
Plant
• Store Food
Roots Control Water Flow:
• The root cortex is beneath the epidermis. The
innermost layer of the cortex, called the
endoderm, is a ring of cells surrounding the
vascular tissue and contains a waterproof
section.
• The waterproof portion is called the Casparian
Strip.
• The Casparian strip forces water to move
THROUGH the cytoplasm of the endodermal
cells.
• Proteins and components of the membrane then
control absorption of water and nutrients toward
the xylem which then distributes them
throughout the plant.
Pathway of water and Minerals
through the roots toward the
xylem
Notice…..Water enters the root through the
epidermis/ cortex cell walls and membrane. It
can NOT enter into the root after the
Casparian strip. Instead passes only through
the cell interior toward the xylem!!
Root Pressure:
• High mineral concentration
inside vascular tissue attracts
water due to osmosis.
• This pressure from incoming
water pushes fluids up the
xylem against gravity due to
root pressure.
• This moves water away from
the roots and more water can
enter root tips.
Monocot
Dicot
Types of Roots:
Lateral
Roots
• TaprootsCommon in dicots
• Lateral RootsExtensions off the
taproot
• Fibrous roots –
Common in monocots
Taproot
STEMS:
STEMS – Part of the “SHOOT” system
• Vascular bundles run its length
– Monocots: scattered throughout
– Dicots: arranged in a ring around the edge
Stem
Growth:
• Primary Growth –
apical meristem
at tips.
• Secondary
Growth – Lateral
meristem, adds
layers of vascular
tissue.
– Wood is
secondary
growth xylem
accumulated
over the years!
LEAVES:
Organized to maximize sugar production.
Waxy cuticle cover minimizes water loss
Leaf mesophyll contains the palisade mesophyll,
important for photosynthesis and spongy mesophyll,
for diffusion of gasses into and out of the leaf.
Veins contain vascular bundles for carrying water
and nutrients from soil to the leaves and products of
photosynthesis away from the leaves to other parts
of the plant.
Stomata regulate water loss and gas exchange
Leaves of Monocots
such as Corn have
many Vascular
Bundles of similar
dimensions.
Dicot leaves have a
large central
Vascular Bundle with
smaller and smaller
Lateral Bundles.
Bundle Sheath:
• Specialized cells that surround veins.
• Important in photosynthesis for C4 plants
– Allows plant to bind CO2 with PEP on hot days.
Bundle Sheath cells are impermeable to CO2
Transpiration
is a force that pulls
water from the soil
through the roots
and to the rest of
the plant.
Water evaporates through the leaves and
creates a “suction” effect which enforces the
water to be sucked through the stem.
Water is sucked from the lower
part of the plant to the leaves,
from where it escapes into the
surroundings, through the
vascular bundles. This is
called the transpiration
stream.
4 factors which control rate
of transpiration are :
1)light intensity,
2)humidity,
3)air movement,
4) temperature.
PLANT HORMONES:
Stimulates cell division and elongation
especially in the stems of plants.
Mediates bending in response to gravity ( gravitropism )
and light ( phototropism)
Stimulates root initiation on plant cuttings
Auxin responsible for preference to grow taller vs. to grow
lateral in width.
Synthetic auxins are used as weed killers.
Can cause seedless (parthenocarpic) fruit development.
First plant hormone to be discovered.
• Works ALONG WITH auxin to promote cell division
and leaf enlargement.
• Works AGAINST auxin because it stimulates the
growth of lateral buds .
• Delays senescence ( aging). Used by florists as a
preservative on flowers.
• Produced in plant roots, move up to other tissue.
Stimulates stem & leaf elongation.
Work ALONG WITH auxins to
promote cell growth.
Used to stimulate growth of seeds
after dormancy, and rapid growth
of floral stalks (to help ensure
pollination).
This hormone is a GAS.
Promotes fruit ripening. As fruit ripens it releases more
ethylene causing neighboring fruits to ripen also.
Stimulates flower abscission ( die/ fall off plant) .
Stimulates leaf abscission ( dies/ falls off plant).
Produced in large quantities when a plant is stressed by
Drought, injury, disease or flooding.
Works against auxins.
ASEXUAL REPRODUCTION:
• Plants can be
“cloned”.
• Cuttings, grafts, and
runners allow for a
plant to reproduce
new, genetically
identical individuals.
SEXUAL REPRODUCTION
in Gymnosperm:
 Gymnosperms do not produce flowers.
 Seeds are produced inside cones.
 In gymnosperms the cone is the female reproductive part
and the pollen is the male reproductive part.
 Gymnosperm produce two types of cones.
 The male cone is called the pollen cone.
 The larger female cone is the seed cone.
 A single tree usually produces both pollen and seed
cones.
Female Pine Cone
Male Pine Cone
• Pollination
– Pollen grain lands on stigma
– Pollen tube grows toward ovary
– Two sperm nuclei travel down pollen
tube
– One sperm fertilizes the egg, second
sperm fertilizes the 2 polar bodies
and becomes the 3n endosperm &
becomes the embryo’s food.
• This process is called double
fertilization.
Polar nuclei
Seed Development
• After fertilization
– Ovule becomes
the seed.
– Ovary becomes
the fruit
• Seed consists of:
– Seed coat
– Embryo
– Cotyledon ( food
for embryo)
• Seeds packaged into an
attractive box-
FRUIT.
• Various fruit forms provide
different types of dispersal :
– Fruit eaten by animal,
seed just discarded.
– Fruit digested by animals,
seeds released in feces.
– Burs carry seeds on fur.
– Winged fruits use the
wind for dispersal.
Seeds Differ Between
Monocots and Dicots:
Growth of a Plant Toward or Away
From a Stimulus.
• Phototrophism – growth toward light.
• Gravitropism-growth away from gravity.
• Thigmotropism- growth around object
when in contact with the plant.
• Caused by the unequal
accumulations of Auxin.
• Auxin accumulates on
the dark side of a plant.
• Cells containing auxin
will elongate faster.
• Faster growth on the
dark side causes plant to
tilt toward the light.
A key regulatory
process in plants to
insure that roots grow
down and shoots grow
up in developing
seedlings
The result of the
hormones Auxin and
Gibberellin.
Touched cells produce Auxins and
transport it to untouched cells. Some
untouched cells will then elongate
faster so growth Bends around the
object.
Plants can respond to day length to control
many activities, among them being the
flowering of various species. This ability to
respond to day length is linked to an inner
light sensitive circadian rhythm.
Flowering plants can be classified as long
day, short day or day neutral plants.
Plants use the pigment phytochrome to
sense day length or photoperiod. It is
sensitive to red light waves of daylight.