Compiled Notes for the following outcomes: Identify plant structure Describe the functions for each plant structure Explain the transportation of water and nutrients in xylem Explain the transportation of nutrients in phloem

1. TOPIC
6:
PLANT
STRUCTURES

2. Learning
outcomes
• Iden=fy
plant
structure
• Describe
the
func=ons
for
each
plant
structure
• Explain
the
transporta=on
of
water
and
nutrients
in
xylem
• Explain
the
transporta=on
of
nutrients
in
phloem

4. Plant
Organs
• Flowering
plants
have
two
major
components
to
their
structure.
1. A
root
system;
extends
below
ground
2. A
shoot
system;
composed
of
the
stem,
leaves,
and
reproduc=ve
organs.
• At
the
end
of
the
root
and
shoot
system
is
a
terminal
bud
from
which
ver=cal
growth,
called
primary
growth,
occurs.

6. Content
1. Leaf:
Structure,
func=on
and
adapta=on
2. Stems:
Structure,
func=on
and
adapta=on
3. Roots:
Structure,
func=on
and
adapta=on
4. Transporta=on
1. Xylem
2. phloem

7.
1.
Leaf
— plants
make
carbohydrates,
occurs
in
the
leaves
via
photosynthesis.
— To
conduct
photosynthesis,
leaves
need
solar
energy,
water,
and
carbon
dioxide.
— Photosynthe=c
leaves
share
similar
structural
components.
— The
blade,
the
wide
part
of
the
leaf
— The
pe=ole,
the
stalk
connec=ng
leaf
to
stem.

8. The
blade:
— the
wide
part
of
the
leaf
— Have
maximum
surface
area
for
the
collec=on
of
energy
&
absorb
CO2
The
pe5ole:
—
the
stalk
connec=ng
leaf
to
stem.
—
receive
H2O
from
the
root
by
way
of
vascular
=ssue
that
terminates
in
the
leaves

9. • There
is
tremendous
diversity
in
leaf
structure
between
plant
species.
• In
some
plant
species,
leaves
may
serve
addi=onal
func=ons,
such
as
storage.
• Some
plants
are
deciduous
(they
drop
their
leaves
during
certain
seasons.)

10. Leaves
adapta5ons
• Modified
as
tendrils-­‐
that
allow
the
plant
to
aZach
to
objects.
• The
leaves
of
cactus
are
spines
that
reduce
H2O
loss
&
protect
the
plant
from
browsing
animals.
• The
leaves
as
traps
for
catching
insects.

11. Organiza5on
of
Leaf
• The
top
and
boZom
of
a
typical
eudicot
leaf
is
composed
of
epidermis
– The
epidermis
o[en
has
hairs
or
glands.
– Stomata
are
located
on
the
lower
epidermis.
• The
interior
of
the
leaf
is
composed
of
photosynthe=c
mesophyll
cells.
– The
spongy
mesophyll
is
arranged
randomly
to
increase
surface
area
for
gas
exchange.
– The
palisade
mesophyll
is
comprised
of
elongated,
ver=cally-­‐
oriented
cells.
Contain
the
most
chloroplast.

14. 2.
Stems
• The
stem
is
the
main
axis
of
the
plant.
• Stems
can
produce
side
(lateral)
branches
from
lateral
(axillary)
buds.
•
Nodes
are
the
points
where
leaves
aZach
to
stems.
• An
internode
is
the
region
between
nodes.

15. • The
stem
also
contains
the
vascular
5ssue
that
transports
water
and
nutrients
to
leaves
(
to
support
photosynthesis).
• In
some
plant
species,
stems
may
also
carry
out
photosynthesis
or
serve
as
a
storage
organ
(e.g.
tuber)
Sweet potato- tuber plant

16. Monocotyledon
Versus
Dicotyledon
Plants
Vascular
5ssue:
— The
arrangement
of
the
vascular
=ssue
differs
between
monocots
and
eudicots.
— Plants
have
two
types
of
vascular
=ssue.
1. The
xylem
transports
water
and
minerals.
2. The
phloem
transports
organic
nutrients.
— The
vascular
=ssues
serve
as
a
type
of
circulatory
system
for
plants.

17. Monocot
vs.
Dicot
Vascular
Tissue
Arrangement
Scattered Forming a ring

18.
3.
Roots
• Roots
system
supports
the
plant
by
anchor
plants
to
the
soil.
• Roots
also
absorb
water
and
nutrients
from
the
soil.
• The
surface
area
of
roots
is
greatly
increased
by
the
produc=on
of
root
hairs.

19. Root
Hair

20. • There
are
different
types
of
root
systems.
1. Some
plants
have
a
single
taproot.
2. Grasses
have
fibrous
root
systems.
3. Some
plants
have
prop
roots;
a
type
of
adven55ous
root
for
support.
Root
system

21. • For
perennial
plants,
the
roots
act
as
a
storage
order
that
allows
the
shoot
system
to
regrow
each
year.
grow and bloom over the spring and
summer, die back every autumn and
winter, and then return in the spring
from their root-stock

22. TRANSPORTATION
OF
WATER
&
MINERALS
:
XYLEM

23. Xylem:
Tracheids
and
Vessel
Members
• Water
and
dissolved
mineral
ions
flow
through
conduc=ng
tubes
of
xylem
• Interconnected,
perforated
walls
of
tracheids
and
vessel
members
(dead
cells)
form
the
tubes

25. 1. The
water
and
nutrients
taken
up
by
roots
and
root
hairs
through
soil
water.
2. H2O
enter
the
root
by
osmosis
3. H2O
+
nutrients
are
transported
to
leaves
via
the
interconnected
vessel
elements
of
the
xylem.
4. H2O
+
nutrients
transported
to
leaves

26. 1.
Root
Pressure
• The
water
and
nutrients
taken
up
by
roots
and
root
hairs
through
soil
water.
• This
movement
is
provided
in
part
by
root
pressure,
a
posi5ve
pressure
created
when
water
enters
the
root
by
osmosis.
• Soil
hypotonic
à
root
hypertonic
Root pressure

27. 2.
Transpira5on
• Transpira=on
– Evapora=on
of
water
from
plant
parts
(mainly
though
stomata)
into
air
– pulls
water
upward
through
xylem
by
causing
con=nuous
nega=ve
pressure
(tension)
from
leaves
to
roots
• root
hypotonic
!
leaves
hypertonic

28. 3.
Cohesion-­‐Tension
Theory
• The
cohesion-­‐tension
model
explains
how
water
travels
up
the
xylem
to
leaves.
• leaves
have
numerous
openings
called
stomata.
• When
these
stomata
are
open,
water
evaporates
from
the
interior
of
the
leaf
to
the
outside
air,
a
process
called
transpira=on.

29. Cohesion-­‐Tension
Theory
1. As
plant
leaves
transpire
water,
a
tension
is
created
that
pulls
water
from
roots
to
leaves.
2. This
tension
is
maintained
because
water
molecules
display
an
aZrac=on
to
one
another
called
cohesion.
3. Hydrogen
bonds
among
water
molecules
resist
rupturing
(cohesion)
so
water
is
pulled
upward
as
a
con=nuous
fluid
column
4. Water
also
adheres
to
the
xylem
elements
in
a
process
called
adhesion.
5. Hydrogen
bonds
break
and
water
molecules
diffuse
into
the
air
during
transpira=on
Cohesion &
adhesion
Transpiration

30. Root pressure
created when
water enter root
cells via osmosis
Water rises through xylem
vessels because :
1. Cohesion: Water
molecules are
attracted to each
other
2. Adhesion: Water
molecules form
hydrogen bonds with
the xylem cell wall
Transpiration
Evaporation of water from
stomata creating a tension
that pulls the water column
from root to leaf
** Because of cohesion, new water molecules is drawn from the xylem which is
replaced by water from the roots

31. Opening
and
Closing
of
Stomata
— The
opening
and
closing
of
the
leaf
stomata
is
controlled
by
turgor
pressure
within
the
guard
cells.
— As
water
enters
the
guard
cells,
these
cells
swell,
opening
the
stomata.
— As
water
exits
the
guard
cells,
the
loss
of
turgor
causes
the
stomata
to
close.

32. Water
Conserva5on
• Cu5cle
– Waxy
covering
that
protects
all
plant
parts
exposed
to
surroundings
– Helps
the
plant
conserve
water

33. Water
Conserva5on
• Environmental
signals
cause
stomata
to
open
and
close
• Closed
stomata
limit
water
loss
(but
prevent
gas
exchange
for
photosynthesis
and
aerobic
respira=on)
• Some
plant
like
CAM
plant
adapt
for
water
conserva=on
and
photosynthesis
by
opening
their
stomata
at
night
to
allow
CO2
for
photosynthesis
and
close
stomata
during
the
day
to
prevent
dehydra=on.
The pineapple
is an example
of a CAM plant.
CAM= Crassulacean acid metabolism

34. TRANSPORTATION
OF
ORGANIC
NUTRIENT:
PHLOEM

35. Phloem:
Sieve-­‐Tube
Members

36. perforated end
plate of sieve-tube
Cell (sieve plate)
one of a series of
living cells that abut,
end to end, and form
a sieve tube
companion cell (in
the background,
pressed tightly
against sieve tube)
Phloem:
Sieve-­‐Tube
Members

37. Organic
Nutrients
in
the
Phloem

38. • As
mature
leaves
photosynthesize,
phloem
load
sucrose.
• Phloem
is
considered
source
of
sugar
(Source
cell).
• The
phloem
transported
sugar
to
=ssues
that
require
sugars,
called
sink
=ssues
(Sink
cell).
• Sugar
are
unloaded
at
sink
region
(ac=vely
growing
or
storage
parts
of
the
plant
)

39. Pressure
flow
theory
• Phloem
– Translocate
photosynthe=c
products
down
the
gradient
of
pressure
and
solute
concentra5on
• Transloca5on
Process
– Distributes
sucrose
and
other
organic
compounds
throughout
the
plant
– An
energy-­‐requiring
process
– Can
be
elaborate
by
Pressure-­‐flow
theory
Translocation

40. 1. Source
cells:
produce
glucose/
organic
molecules
(by
photosynthesis)
2. Glucose
is
converted
to
sucrose
for
transport
3. Companion
cell
loads
sucrose
4. Water
follows
from
xylem
by
osmosis
5. Sap
volume
and
pressure
increased
6. Sap
flow
within
phloem
7. Unload
the
organic
molecules
by
the
companion
cell
8. Sucrose
is
stored
in
sink
cell/
=ssues
(as
starch)
9. Water
diffuses
into
xylem
10. Water
recycles
as
part
of
transpira=on
to
re
supply
the
sucrose
loading
(1)
(2)
(3)
(4)
(5)
(7) (8)
(9)
(10)
Pressure
flow
theory
(6)
glucose

41. https://www.youtube.com/watch?
v=MxwI63rQubU
https://www.youtube.com/watch?
v=60SgZgK3Gss