Plant Transport Flashcards
Why do we need plant transport systems?
- High Metabolic Demand
- Low SA: V Ratio
- Long Distance from external surface to cells
- Ensures molecules reach all tissues
Explain how water enters the endodermis in root cells?
- Ions enter via active transport
- Lower water potential
- Water moves in by osmosis
Why do we need plant transport systems?
- High metabolic demand
- Low SA:V Ratio
- Diffusion rate is not sufficient
- Long distance from external surfaces to cells
- Ensures nutrients/molecules reach all parts of the plant
Why do plants need water?
- Evaporation to keep them cool
- Nutrients/Molecules travel in aqueous medium
- Turgor pressure for cell expansion
- Raw material for photosynthesis
What is the parenchyma?
Support tissue
Adaptations of root hair cells?
- High SA: V Ratio
- Lots of them!
- Microscopic size: penetrate between soil particles easily
- Maintain water potential gradient
- Thin CSF
Adaptations of xylem?
- Immature cells produce lignin which kills the cells.
- Lignin for mechanical strength and support
- No end cell walls to allow for continuous stream of water
- Dead
- Non lignified boarder pits to allow for lateral movement of water
- Lignin to reinforce the plant wall against the transpiration pull
Where is a companion cell located?
Vascular tissue
What does a companion cell transport?
H+, Assimilates e.g sucrose
What does a root hair cell transport?
Mineral ions e.g Nitrate Ions
How does the Casparian Strip prevent ions from reaching the xylem of the plant by the apoplast pathway?
- Strip is impervious to water/ solutions
- Forces water to pass through cell surface membrane
- Phospholipid bilayer repels ions (hydrophilic molecules due to its hydrophobic core)
Explain why water molecules can form hydrogen bonds with nitrate ions.
- Water is a polar molecules
- Nitrate ion is charged
- Hydrogen bonds form between H on water and O on nitrate ion
A group of students want to observe the xylem, how should they go about this?
- Put leaf in dye
- Cut a transverse section
- Observe under low power under a light microscope
How do xeropohytes xylem differ to hydrophytes xylem?
- Hydrophytes have no lignin (water provides turgor pressure for strength)
- Xerophytes have thinner walls
A similarity between xylem and phloem?
- Both made up of cells joined end to end
- Xylem vessels and phloem sieve tube elements both lack nuclei
Differences between xylem and phloem?
- Lignified
- Sieve tube elements
- Companion cell
- End Walls
- Bordered pits
- Cytoplasm
- Vessels
What is the function of the bordered pits?
Lateral movement of water
What are the precautions when using a potometer?
- Do not allow air to enter to ensure continuous stream of water
- Keep abiotic factor constant as it affects the rate of transpiration
- Keep screw clip closed to prevent entry of water whilst measuring
Describe how a potometer can be used to achieve a more accurate transpiration rate.
- Potometer airtight
- Dry leaves
- Cut shoot under water/ Slanted cut
- Measure distance air bubble travels during a fixed time interval
- Constant conditions
Suggest three ways in which students could improve their tree sampling method.
- Same / similar, size / age, trees/ leaves
- Repeat and calculate mean
- Record at same time of day/year
- Evenly distributed around the tree
- Systematic sampling / sample at set distances
The students concluded that there is a positive correlation between distance of the tree from
the river and mean leaf hair density.
Suggest reasons for this positive correlation.
- Further away from river there is less water available
- Transpiration causes water loss
- Hairs trap water vapour
- Reduced water potential gradient inside and outside the leaf
Suggest how water is being lost from the cut stem when all the leaves have been treated with
petroleum jelly.
- Evaporation from upper leaf surfaces.
- Epidermis/ Cuticle
State what assumption is made when using this apparatus to measure the rate of
transpiration.
Transpiration equals uptake.
Symplast Pathway
