8. Transport in Plants Flashcards
What does the xylem transport?
Water and minerals.
What does the phloem transport?
Sugars (eg. sucrose and amino acids)
Describe the position of the xylem and phloem in the leaf
The xylem is on top of the phloem.
Describe the position of the xylem and phloem in the roots
The xylem is in the middle of the root in an X shape. The phloem is on the outside of the xylem.
Describe the position of the xylem and phloem in the stem
The xylem is on the inside of the stem, the phloem is on the outside of the xylem.
Describe the pathway of water through a plant
- Root hair cell
- Root cortex cell
- Xylem
- Mesophyll cells
How do you investigate the pathway of water
through a plant?
- Place a plant into a beaker of water with stain added to it
- After several hours, the leaves of the plant should turn the same colour as the dyed water.
- This shows water is being taken up by the plant.
- When a cross-section of the plant is taken, only the xylem vessels will be stained.
Describe the process of transpiration
- Water is lost through the stomata.
- More water is drawn up to replace the lost water.
What is the transpiration stream?
The transpiration stream is the flow of water through a plant.
Define transpiration.
The evaporation of water from the aerial parts of a plant on the surface of the mesophyll cells which is followed by diffusion of water vapour through the stomata.
Why is water lost from plants?
- Plants have large air spaces in them.
- Plants have stomata (pores) in the leaves
which allows water to diffuse out of the plant. - Plants have a large surface area for
evaporation to occur.
How do the interconnecting air spaces affect water vapour loss?
- The interconnecting air spaces between the
mesophyll cells create a large internal surface
area. - This increases the amount of water which can
evaporate from the leaf.
How do the shape and size of stomata affect water loss?
- A greater number of stomata leads to more
evaporation of water vapour from the leaves -
increasing rate of transpiration. - A larger size of stomata also leads to more
evaporation and increases the rate of transpiration.
Explain the movement of water through a plant
- Water evaporates from the leaves creating a
negative pressure in the xylem (transpiration
pull). - Water is drawn up the xylem in a column that is
held together by cohesion.
How does the temperature affect the rate of transpiration?
As the temperature increases, so does the transpiration rate.
How does the wind speed affect the rate of transpiration?
The faster the wind speed, the faster the water is moved away from the plant, creating a steeper gradient and increasing the transpiration rate.
What causes wilting?
A lack of water which means the plant cells are not turgid and so the plant is not supported.
Describe translocation
Translocation is the movement of sugars and amino acids up or down the phloem from source to sink (with the use of energy).
