SB6d Flashcards
What is transpiration?
Transpiration is the process of water movement through a plant and its evaporation through aerial parts of the plant, such as the stomata of leaves and flowers.
What is the potometer?
The rate of transpiration can be measured using the set up below, which is
called the potometer.
What are the 4 environmental factors that affect the rate of transpiration?
Temperature
Humidity
Wind
Light intensity
How does Temperature affect the rate of transpiration?
The higher the temperature the faster molecules move, as they gain kinetic energy (they evaporate faster).
Faster rate of transpiration.
o In the potometer the bubble of air would move faster towards the plant.
How does Humidity affect the rate of transpiration?
The higher the humidity the slower the rate of transpiration as there
is a higher concentration of water vapour outside the leaf.
o Smaller concentration gradient inside and outside the leaf.
o In the potometer the bubble of air would move slower towards the plant.
How does Wind affect the rate of transpiration?
The more the wind the faster molecules will move.
If water molecule around the leaf are blown away, the concentration
of water outside is less, therefore water diffuses out.
o Bigger concentration gradient inside and outside the leaf.
Faster rate of transpiration.
o In the potometer the bubble of air would move faster towards the plant
How does Light intensity affect the rate of transpiration?
When there is more light, plants want to do more photosynthesis.
Stomata would open more losing more water vapour in the process.
Faster rate of transpiration.
o In the potometer the bubble of air would move faster towards the plant.
What is translocation?
Translocation is the movement of substances (nutrients) in various parts of the plant.
Explain the process of translocation.
Sucrose and other molecules is translocated (transported) in the sieve tubes of the phloem tissue.
Companion cells actively pump sucrose into or out of the sieve cells
companion cells push sucrose into phloem cells using energy (active
transport).
As sucrose is pumped into sieve tubes, the pressure increases causing the solution to flow up to growing shoots or down to storage organs (leaves/roots).
Why does translocation occur?
Root cells do not photosynthesise and therefore cannot produce their own food.
Nutrients, like sucrose, need to be transported to these cells by translocation
State the substance transported, the tissues involved, direction of movement and source of movement for both transpiration and translocation.
In Transpiration the substance transported are Water and mineral ions (dissolved in water) while in translocation it is Sucrose and other nutrients
In Transpiration the tissues involved is the Xylem tissue. While in translocation it is the Phloem tissue
In Transpiration the direction of movement is Upwards (against gravity) via capillary action. While in translocation its Upwards AND downwards via the pressure flow hypothesis.
In Transpiration the source of movement is From root hair cells. While in translocation its From photosynthetic cells.
Name the parts of the potometer and their purpose.
Stopper = to hold plant in position and prevent air from escaping
Capillary tube = has scale on it like a ruler so that you can
measure the distance travelled by the bubble.
Bubble = moves in the tube according to how much water is
absorbed by the plant.
Reservoir = to reset the experiment (push bubble back) and try
again.
