Mass transport in plants Flashcards
Role of xylem
Transport of water and mineral ions from the roots up to the leaves
Role of phloem
Transport of sugars from leaves to respiring cells
Roles of water in plants
- Cell turgidity
- Metabolite
- Hydrolysis reactions
- Transport of inorganic ions
By what process are mineral ions taken into root hair cells?
Active transport
Explain movement of minerals and water into xylem
Minerals actively transported into xylem, lowering water potential. Water follows by osmosis
Features of xylem vessels
- Hollow (cells have no end wall)
- Lignified (lignin in cell walls - structural polymer)
- Long continuous tube
- Very rigid (due to lignin forming in helices)
What is the transpiration stream?
Bulk transport of water up the stem of a plant through xylem vessels (passive)
What is transpiration?
Evaporation of water from plants’ leaves
What 3 forces aid movement of water through transpiration stream?
- Pulling force - due to evaporation of water from leaves
- Root pressure - water taken into the roots by osmosis - pushing force
- Capillary action in xylem
What is capillary action?
Combination of adhesion and cohesion, aiding upward movement of water. Continuous unbroken column of water molecules
What factors affect the rate of transpiration?
Temperature
Light
Air movement
Humidity
What do potometers help us do?
Measure rate of transpiration
What is translocation?
Transport of organic molecules from one part of the plant to another
Where does translocation take place?
The phloem
What is the phloem made out of?
- Sieve tube elements with end walls that are perforated by sieve plates
- Companion cells
