for
transporting water
and minerals
in xylem
vessels
10.1
Transpiration in plants
1
Transpiration
creates
transpiration pull

10
Transpiration, transport and support in plants
34
Significance of transpiration
C
10.1
Transpiration in plants
helps
absorption of
water
by roots
2
Transpiration
creates
transpiration pull

10
Transpiration, transport and support in plants
35
cooling effect
Significance of transpiration
C
10.1
Transpiration in plants
3
Evaporation of
water removes heat
from the leaves

10
Transpiration, transport and support in plants
Common misconception
Common misconception
Water moves out of the leaf by osmosis
down the water potential gradient.
36
Water vapour
moves out of the leaf by
diffusion
down the concentration gradient
.
Water losses to the atmosphere by
evaporation.
Water losses to the atmosphere by
transpiration
.

10
Transpiration, transport and support in plants
37
How are stomata distributed
on leaves?
D
10.1
Transpiration in plants
•
different plants have different
numbers
and
distribution
of stomata
on leaves
•
adaptations
to different environments

10
Transpiration, transport and support in plants
38
Distribution of stomata on leaves
Terrestrial dicotyledonous plants
10.1
Transpiration in plants
Tomato
Stomatal density
(number per cm
2
)
Upper
epidermis
Lower
epidermis
1200
13 100
lower density

10
Transpiration, transport and support in plants
39
10.1
Transpiration in plants
Distribution of stomata on leaves
Submerged plants
Hydrilla
Stomatal density
(number per cm
2
)
Upper
epidermis
Lower
epidermis
0
0
no stomata

10
Transpiration, transport and support in plants
40
10.1
Transpiration in plants
Distribution of stomata on leaves
Submerged plants
Hydrilla
no cuticle
gases, water and
minerals
diffuse
directly
through all
surfaces

10
Transpiration, transport and support in plants
41
10.1
Transpiration in plants
Stomatal density
(number per cm
2
)
Upper
epidermis
Lower
epidermis
Water lily
9500
0
no stomata
Distribution of stomata on leaves
Floating plants

10
Transpiration, transport and support in plants
42
10.1
Transpiration in plants
Water lily
no cuticle
lower epidermis
Distribution of stomata on leaves
Floating plants

10
Transpiration, transport and support in plants
43
10.1
Transpiration in plants
Water lily
gas exchange
through stomata
water and minerals diffuse directly
lower epidermis
upper epidermis
Distribution of stomata on leaves
Floating plants

10
Transpiration, transport and support in plants
44
Structural adaptations of
leaves to prevent excessive loss
of water through transpiration
E
10.1
Transpiration in plants
terrestrial plant

10
Transpiration, transport and support in plants
45
10.1
Transpiration in plants
cuticle
impermeable to water
reduce water loss
1
Covered with cuticle

10
Transpiration, transport and support in plants
46
10.1
Transpiration in plants
sun
2
Fewer stomata on upper epidermis
dicotyledonous plant
leaf held horizontally

10
Transpiration, transport and support in plants
47
10.1
Transpiration in plants
few or no stomata
sun
temperature
reduce water loss
2
Fewer stomata on upper epidermis

10


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- Fall '09
- Xylem , Transpiration