Plant Transport Flashcards
Why do plants require a transport system
High metabolic demand
Multicellular plant so diffusion won’t be quick enough to ensure cells receive strong supply of nutrients
Small SA:V ratio
Relate the structure of xylem to its function
Long,continuous columns made of dead tissue , allowing transportation of water
Contain pits,allow water to move sideways between vessels
Thickened woody substance called lignin to provide structural support and prevent collapse inwards
Relate the structure of phloem to its function
Plasmodesmata to allow flow of substances between cytoplasm of different cells
Sieve tube elements to transport sugar around the plant
Companion cells designed for active transport of sugars into tubes
Describe the structure and function of the vascular system in the roots
Consists of xylem and phloem
Xylem arranged in an X shape to provide resistance against force
Describe the structure and function of the vascular system in the stem
Consist of xylem and phloem
Xylem on the inside of the bundle to provide support
Describe the structure and function of the vascular system in the leaves
Consists of xylem and phloem, forms due midrib and veins
Involved in transport and support
Define transpiration
The evaporation of water from the leaves of a plan as a result of gaseous exchange
What are the factors that affect the rate of transpiration
Increased light
Increased temperature
Increased humidity decreases transpiration
Increased air movements
How can we measure transpiration rate
Photometer
Place the cut plant in a water filled tubes that contains one air bubble
Define water potential as a mechanism of movement in plants
Water potential =the likely hood of water to move by osmosis down a conc gradient
Explain the apoplastic pathway
Water moves through the cell walls and intercellular spaces
Can be used until water reaches Casparian strip
Explain the symplastic pathway
Water moves through the cytoplasm via plasmodesmata
Water must be actively transported into cells
Explain the cohesion tension theory
- water molecules from hydrogen bonds with each other, causing them to stick together
- surface tension of water creates sticking effect
- when water is lost via transpiration more can be drawn up the stem
What are the adaption of XEROPHYTES that allow them to live in dry conditions
- Thick waxy cuticle
- Stomata often closed
- Hair to trap moist air
What are the adaptation of HYDROPHYTES that allow them live in wet condition
Stomata often open
Air space for buoyancy
Wide , flat leaves
How does translocation occur
Sucrose produced in leaves loaded into sieve tubes via active transport
Lowers water potential
Water move in from xylem
Assimilates move along sieve tube towards areas of lower hydrostatic pressure
Sucrose diffuses into surrounding cells
How can you estimate the rate of transpiration
Using a potometer
How can you investigate transpiration by using a potometer
1) Assemble potometer in water and insert shoot underwater
2) remove out of water BUT keep end of the capillary tube submerged into beaker of water
3) check if it’s air/water tight
4) Remove end of capillary tube from beaker until one air bubble had formed
5) record starting position of air bubble
Why does putting a leaf with a bag effect transpiration
Increases humidity
Which increases transpiration
What do plant organelles consist of
Vacuoles - cell sap
Chloroplasts - photo synthesis
What is unique about plant cell walls
Rigid structure
Made of cellulose(beta glucose) - permeable substances can go in and out
Act as defensive mechanism, protect from invading pathogens
Gives shape
Name and describe two pathways that water takes to reach xylem vessels at the base of the stem
Symplast- passing through the cytoplasm
Apoplast-between the cell walls
Explain why movement of amino acid at the roots can maintain a pressure gradient along the phloem
At roots,substances produced in the leaves are likely to be unloaded from the phloem
Increases water potential in the sieve tubes, water then leaves
Reduces pressure inside sieve tube, root< leaf end
Give one similarity and one difference between the position of the phloem in a transverse section of root tissue compared with a transverse section of stem tissue
Similarity: phloem is more towards the outer edge of the plant then the xylem
Difference : root,surrounds one central mass of xylem cell rather then discrete bundle in stem
