Transcript Transport in plants (13.4) and Plant Reproduction

Transport in plants (13.4)
and
Plant Reproduction
5.3
Plant Tissues
 Groups of
specialized cells
form tissues
except when
dormant (ex.
during extreme
cold or heat)
 These tissues
include dermal,
ground and
vascular tissue.
Plant Tissues Located In Various Organs
Dermal
tissue
• Dermal tissue forms the outermost covering
of the plant’s organs. It forms a protective
barrier and controls the exchange of water
and gases between the plant and its
environment. An epidermal cell is one type
of cell that forms dermal tissue.
Ground tissue
 Ground tissue
has several
functions
 Some ground
tissue is
responsible for
photosynthesi
s, other tissues
provide
support for the
plant’s body
Vascular Tissue
 Vascular tissue is
responsible for
transporting
water, nutrients
and sugars
throughout the
plant (ex. xylem
and phloem)
 It also helps to
provide physical
support for the
plant’s body
Vascular tissue
(Xylem & Phloem)
• Xylem
transports
water and
minerals from
plant roots to
other parts of
the plant
• Phloem
transports
sugars from
leaves to other
parts of the
plant
Sugar and Water Movement in
Plants
Transpiration
• 90% of water that enters the leaf is lost out
of stomata through transpiration
How is water transported 100m up
without muscles?
• Positive pressure
(pushing)
– Root pressure
• Negative pressure
(pulling)
– Transpirational pull
Water Movement
• Water is moved up
from the roots of the
plants, up the stem
and out the leaves by
the Transpiration-Pull
Theory (CohesionTension pull theory).
Water Movement
•
The theory is based on
the three key properties
of water:
1) Cohesion: the ability of
water molecules to stick
together
2) Adhesion: the ability of
water molecules to stick
to the sides of hollow
tubes.
3) The high surface
tension of water.
Water Movement
• Water molecules are
absorbed into the
roots through the
process of osmosis.
• Here water is forced
through the
endodermis into the
xylem, but only if the
xylem has room for it.
Water Movement
• At the leaves, water is
being used in
photosynthesis or it is
evaporated out of the leaf
through the stomata (a
process known as
transpiration)
• Due to the cohesion of
water molecules, as one
is pulled out of the
stomata or used in the
leaf, another takes its
place.
Water Movement
• Due to adhesion, the
water is able to stick
to the sides of the
xylem tubes and not
slide back down
towards the root.
Water Movement
• This occurs
throughout the entire
length of xylem in the
plant!
• Due to these
properties, water can
be pulled against the
force of gravity
upwards of hundreds
of feet!
Water Movement
• As water is being
pulled up through the
stem, more water is
forced through the
endodermis of the
root to replace water
lost at the leaves, so
there is a continual
flow of water through
the plant.
Sugar Movement
Sugar Movement
• This process is known as the PressureFlow Theory
• It was suggested by Ernst Munch, a
German plant physiologist, in 1926.
Sugar Movement
1. Glucose is created
at the leaf (The
Source) during
photosynthesis.
Glucose is changed
into the disaccharide
sucrose in order to
be transported in the
plant.
Sugar Movement
2. This sucrose is
actively transported
(uses energy) into
the phloem cells in
the leaf.
3. There is a high
concentration of
sugar (sucrose) in
the phloem at the
source.
Sugar Movement
4. Because there is so
much sugar in the
phloem, some water
moves in from the xylem
to try and balance out
the concentration.
5. This creates a high
amount of pressure in
the phloem near the
source.
Sugar Movement
6. Meanwhile sugar is being actively transported
into the root or any other storage area in the
plant (The Sink).
7. Sinks have lots of sugar (usually joined
together to form starch).
8. The phloem cells around a sink have low
amounts of sugar and therefore water will leave
them and cause them to have a low amount of
pressure.
Sugar Movement
Sugar Movement
9. Due to the difference in pressure in the phloem cells at
the Source and the Sink, sugar will be forced down the
phloem along this pressure gradient.
• http://www.youtube.com/watch?v=-b6dvKgWBVY
Learning Check
• Pg 563, Q 25-30
• Pg 566, Q 1,2,3
Plant Reproduction
Angiosperms (flowering plants)
• Plants that protect their seeds within the
body of a fruit.
• Make up ¾’s of all plants, including:
– Trees, shrubs, herbs,
grasses, water plants…
Structure of a Flower
1. Pistil
2. Stigma
3. Style
4. Ovary
5. Stamen
6. Filament
7. Anther
8. Petal
9. Sepal
10. Receptacle
11. Stem
Male Reproductive Structure
The stamen consists
of two parts: Anther
and Filament
The anther is where
meiosis occurs to
produce haploid
pollen
The filament is a stalk
that supports the
anther
Female Reproductive Structure
The pistil consists of
the stigma, style and
ovary
The sticky stigma
receives the pollen
from the anther
The pollen grows a
tube down through
the style
Meiosis occurs in
the ovary to produce
haploid ovules
Reproductive Structures
• Petals: colourful
structures that attract
pollinators.
• Sepals: surround and
protect the flower
bud.
Learning Check
• Pg 584, Q 1-6
Structural Differences
• Complete Flowers
– Sepals, petals, stamens and pistils
• Incomplete Flowers
– Missing one or more of the above
• Perfect Flowers
– Have both pistils and stamens
• Imperfect Flowers
– Have either pistils or stamens, but not both
• Monoecious
– plants have individual flowers that are
imperfect but they have both male and female
flowers (oaks, corn)
• Dioecoious
– Plants that have reproductive structures
divided between two plants (willow)
Pollination
• Self-pollinating plants
– Pollinate themselves (either same flower or
elsewhere on plant
– Loss of genetic variation
• Cross-pollinating plants
– Most angiosperms
– Receive pollen from another plant
– Ensures genetic diversity
Pollination
Wind, insects or other
animals transfer
pollen from the anther
of one flower to the
stigma of another
Flowers vary
depending on
pollination
mechanism
Pollination Vectors
Wind Pollination: Dull, scentless
flowers with reduced petals
Bees/Butterfly Pollination: Bright
color, nectaries, scent.
They sip nectar, get pollen on coats,
transfer pollen from flower to flower
Bird Pollination: Nectaries, bright
colors, tube-like flowers
Moth Pollination: White petals,
open at night
Fly Pollination:Rank odor, flesh
colored petals
Seed and Fruit Development
After fertilization,
the petals and
sepals fall off
flower
Ovary “ripens”
into a fruit
The ovule
develops into a
seed
Seed Dispersal MechanismsAllow plants to colonize new areas and
avoid shade of parent plant
Wind Dispersal - Flight mechanisms,
like parachutes, wings, etc.
Ex. Dandelion, maples, birch
Animal Dispersal - Fleshy fruits which
animals eat, drop undigested seeds in
feces or burrs which stick to
animals’ coats
Gravity Dispersal Heavy nuts fall to
ground and roll
ex. acorns
Water Dispersal - Plants
near water create floating
fruits
ex. coconuts
Learning Check
• Pg 586, Q 7-12
• Pollen
Grain
• Anther
Sac
Pollen grains contain two haploid cells produced through meiosis.
1- The Tube cell – will grow the pollen tube.
2- The Generative cell – will go through mitosis to create
two sperm cells.
Ovary
Each ovule within an ovary has a micropyle (an opening for the
pollen tube).
The ovules’ megasporangium undergo meiosis to produce four
haploid cells (3 die leaving 1 megaspore)
The megaspore undergoes mitosis 3 times to produce 8
haploid cells within the embryo sac.
Fertilization
After pollen lands on the stigma, a pollen
tube grows down through the style to
ovary
Generative cell creates the two sperm
nuclei
Double fertilization occurs:
one sperm fertilizes the egg
 one sperm the two polar nuclei together
Result of Double Fertilization
The sperm nucleus and egg nucleus join
to form a 2n (diploid) embryo
The other sperm nucleus and the two
polar nuclei join to form a 3n (triploid)
endosperm. The endosperm is the food
supply for the embryo.
First link
SEED GERMINATION
• Seeds initially germinate as they absorb
water, bursting the seed coat so the
growing plant can produce energy
• This starts a chain of chemical reactions
which will result in the development of a
plant embryo
STEPS IN SEED GERMINATION
1. Water is added (most important)
– Activates enzymes necessary for cellular respiration in
the maturing seedling so it can produce the energy
needed to grow
2. Seeds are exposed to heat
– Chemical energy in seed’s starch is converted to
glucose during germination
3. Seeds are exposed to light
– Chemical energy in seed’s starch is converted to
glucose during germination
4. Oxygen is available
Seed Germination
• Radicle is first part of
embryo to appear
(develops into root)
• Hypocotyl appears above
soil (photosynthetic tissue)
SEED DORMANCY
• Dormancy is the block of complete germination of a
viable seed under favourable conditions
• Advantage: Germination is delayed until conditions are
favourable for the survival of both the seed and the
maturing plant
– Ex. Even though some conditions are favourable in
late November, dormancy occurs due to the onset of
winter.
• Seed banks are a plant strategy to ensure that not all
the seeds of one species germinate in a single year. This
insurance save a species in the event of a catastrophic
drought, extreme cold, etc.
Jigsaw
• Each person take two techniques in
artificial propagation and explain it to the
class (pg 590-591)