Translocation Of Manufactured Substances Flashcards
What is translocation?
The movement of substances manufactured in the leaves during photosynthesis to other parts of the plant
What is the main thing that is translocated in plants?
Sugars (mainly sucrose)
By phloem tissue
What kind of process is translocation?
Active
Requires energy
What are the functions of transpiration?
Transportation of water and mineral salts
Cooling of the plant
Why does transpiration cause cooling?
The evaporation of the water cools the plant
What seven adaptations prevent excess transpiration?
Size of leaf Thorns Leaf organisation Position of the stomata Sunken stomata Hairs on the leaves Thickened cuticle
How can the size of leaves prevent water loss?
The smaller the leaves, the smaller the surface area for evaporation
How do thorn prevent excess water loss?
Have fewer stomata
Limit transpiration
How does leaf organisation prevent water loss?
If leaves are vertical, then sunlight absorption will be limited at the hottest time of day
Lower leaves could be shaded by leaves higher up
How does the position of the stomata prevent water loss?
If stomata are placed on the underside of the leaf, then they are not exposed to as much heat
Transpiration is then limited
How can sunken stomata prevent water loss?
The region just outside sunken stomata traps air that is saturated with water vapour
The diffusion rate is kept low
Transpiration is limited
How do hairs on leaves prevent water loss?
They trap water vapour
Reduce the diffusion gradient
Limit transpiration
How does a thicker cuticle prevent water loss?
The thicker the cuticle the less evaporation takes place
What four external factors influence transpiration?
Temperature
Light intensity
Humidity
Wind
How does temperature affect transpiration?
Kinetic energy of the water and air increases
Diffusion occurs faster
Transpiration rate therefore increases with a higher temperature
How does light intensity affect transpiration?
More sunlight leads to more photosynthesis
More water is needed from the roots
Transpiration therefore increases with a greater light intensity
How does humidity affect transpiration?
More moisture in the air
Reduces the diffusion gradient
Diffusion occurs slower
Transpiration therefore decreases when there is a greater humidity
How does wind affect transpiration?
Wind removes the accumulated water vapour just outside the leaf
Diffusion gradient increases
Transpiration therefore increases when there is more wind
What is wilting?
It is when the turgor pressure on plant cells decreases
The structure of the plant deteriorates
The plant goes soft and floppy
When does wilting occur?
When the plant loses more water through transpiration than is absorbed by the roots
How can wilting be reversed?
If the plant absorbs more water
What is guttation?
When the plant loses water through hydathodes instead of through the stomata
When does guttation occur?
When there is high humidity
Why does guttation occur?
Humidity causes the diffusion gradient - needed for transpiration - to be reduced
The plant absorbs more water than it releases
Water droplets are squeezed out of the hydathodes
How can you tell whether guttation or transpiration is occurring?
Guttation: water in liquid form
Transpiration: water in gaseous form
What force plays a role in guttation?
Root pressure
What device can be used to test the effect of external factors on transpiration?
A potometer
