Transport in plants Flashcards
State three features of the leaf hown above which indicate that it live in a dry environment and explain these features (6)
- thick cuticle - waterproofing
- curled - trapping water
- hairs - trap water
- sunken stomata - trapping water vapour
- surface area - less area which water can be lost
What is the name given to plants that live in dry environments (1)
xerophytes
What the role of the xylem (1)
- transports water and minerals
What is the role of phloem (1)
- transports sucrose and amino acids
Explain how epidermal cells carry out its function in the uptake of water and minerals in the plant (4)
- waterproof as casparian strip is impregnated in suberin
- blocks apoplast pathway
- active trasport of minerals by endodermal cells
- into symplast pathway
- active tranport of minerals into pericycle
- water follows via osmosis
- water and mineral ions move into xylem vessels
Explain what is meant by transpiration and th factors affecting transpiration (7) describe how you use a potometer to investigate one of these factors(3)
Transpiration
* evaporation of water vapour from inside the leaves and stem of a plant
* through the stomata
* down a water potential gradient
* high temperature increases rate of transpiration
* increasd kinetic energy increase rate of movement of water molecules
* increased air movement increases transpiration
* increasing diffusion gradient
* high humidity decreases rate of transpiration
* decreased diffusion gradient
* high light intenssity increases rate of transpiration
* because of stomatal opening
Potometer
* set up under water/ make sure it is airtight
* air movement can be changed by using a fan
* volume of water measures per unit of time
* to give a close approximation of transpiration rate
State the process by which plant lose water from their leaves (1)
- transpiration
Describe one theory that would explain how water moves up the stem of the leafy shoot (3)
- water lost from leaves / by transpiration
- causing tension on water molecules
- cohesive forces between water molecules
- adhesive forces between water molecules and xylem
- water molecules pulled ip xylem
- no mention hydrostatic of root pressure
Describe the role of potasium ions in operation of guard cells closing stomata (1)
- pumped out of guard cells
Describe the role of water potential of cells in operation of guard cells closing stomata (1)
- increased water potential so water moves out
Describe the role of unevenly thickened cell walls in operation of guard cells closing stomata (1)
- decreeased water so decreased volume of cell
How does increased humidity affect rate of transpiration and why (2)
- decrease water loss evaporation
- reduces concentration gradient between inside and outside leaf
How does increased temperature affect the rate of transpiration and why (2)
- increase rate of water loss
- greater rate of evaporation from surface of leaf
Describe the uptake of water by plants from the soil into xylem (7) Explain the role of ions in this process (3)
Uptake of water
* water absorbed by root hair cells
* water can move through vell walls
* moves across cortex via apoplast route
* can also move across plasma membrane via osmosis
* water moves from cytoplasm of one cell to the next via plasmodesmata
* called the symplast route
* water can also move through cytoplasm and vacoules via cavuolar route
* casparian sstrip
* made of subein
* stops apoplast route and water forced into symplast route
Ions
* ions absorbed into root hair cells by active transport
* ions lower water potential in root hair cells
* an endodermis ions absorbed into cyctoplasm by active transport
* ions travel through periccle into xylem
* lower water potential in xylem
* lower water potential in root hair cell or xylem increase osmotic gradient between soil and cell contents
State what is meant by the term transpiration (2)
- loss of water vapour
- through stomata
State two practical measures which should be taken when setting up the apparatus to ensure the potometer functions correctly give reasons for your answers (4)
- shoort cut undder watter
- prevent air bubbles entering
- shoot with large number of leaves
- ensure measurable rate of transpiration
- avoid wetting leaves
- blocks stomata
- leave time for apparatus to ettle down
- allow plant to adapt to new conditions
- seal joints with caseline
- prevent air enertering apparatus
- ensure bubble set art appropriate position
- enable suitable reading to be taken