Transpiration

?
What are the causes of transpiration?
Transpiration pull, Capillary action and Root pressure
1 of 27
Transpiration definition
the evaporation of water from the leaves of the plant
2 of 27
How does water move out of the xylem into surrounding cells?
Moves by osmosis, down a water potential gradient, from an area of high water potential to low water potential.
3 of 27
Why is water potential low in palisade mesophyll tissue?
Evaporation in the mesophyll tissue leads to a low water potential
4 of 27
How does water move out of the plant?
Water vapour diffuses out of the stomata, down a water vapour potential gradient from an area of high water vapour potential to an area of low water pptential.
5 of 27
What creates the transpiration pull?
Diffusion of water vapour out of leaf 'pulls' on the coloumn of water in the xylem vessel.
6 of 27
Cohesion definition
water molecules are attracted to each other be hydrogen bonds
7 of 27
Why does water have cohesive forces?
water is polar, and therefore has hydrogen bonds
8 of 27
Cohesion-tension theory
Water vapour diffusing out of stomata exerts a 'tension' or pull on the chain of water molecules in the xylem vessels.
9 of 27
Capillary Action
Water attracted to lignin in outer walls of xylem vessel (adhesion), lignin is polar, forces of attraction between water and lignin, water sticks to vessel.
10 of 27
What are the three pathways of water?
Apoplast pathway, symplast pathway, vacuolar pathway
11 of 27
Apoplast pathway
water moves through cell walls, until casparian *****
12 of 27
Symplast Pathway
water moves through cytoplasm
13 of 27
Vacuolar pathway
water moves through vacuoles and cytoplasm
14 of 27
Root pressure
Pumping of mineral ions into roots via active transport, increases hydrostatic pressure
15 of 27
What is the purpose of the casparian *****?
stops the apoplast pathway when it reaches the endodermis, water has to move into cells
16 of 27
What is the casparian ***** made out of?
suberin (thick waxy band) - impenetrable
17 of 27
How does water moving through the apoplast pathway move across the endodermi?
water must move into cytoplsm
18 of 27
How does water enter into the xylem vessels?
water enters through bordered pits, mineral iond are actively transported into the xylem
19 of 27
What are the factors that affect rate of transpiration?
Thickness of waxy cuticle, humidity, wind speed, temperature, stomatal density, surface area of leaves and light intensity
20 of 27
Thickness of waxy cuticle
acts as a hydrophobic layer, repels water than lands on leaves, prevents too much evaporation
21 of 27
Humidity
Increased humidity means increase in water vapour, water vapour potential gradient becomes less steep, less diffusion out of stomata
22 of 27
Wind Speed
Increased wind speed, more water vapour blown away faster, lowering water vapour potential, steepening gradient
23 of 27
Temperature
Higher the temperature, more kinetic energy, faster rate of evaporation of water to water vapour inside air spaces.
24 of 27
Stomatal Density
The more stomata there is, the more water vapour diffuses out of the leaves
25 of 27
Surface area of leaves
The larger the surface area the more evaporation occurs
26 of 27
Light intensity
Increased light intensity, increases ATP production within guard cells, increasing active transport of potassium ions into guard cells, increases water movement into guard cells, turning it turgid and opening up stomata
27 of 27

Other cards in this set

Card 2

Front

Transpiration definition

Back

the evaporation of water from the leaves of the plant

Card 3

Front

How does water move out of the xylem into surrounding cells?

Back

Preview of the front of card 3

Card 4

Front

Why is water potential low in palisade mesophyll tissue?

Back

Preview of the front of card 4

Card 5

Front

How does water move out of the plant?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Human, animal and plant behaviour resources »