Topic 3 Transport in plants Flashcards
Why can unicellular organisms rely on diffusion?
- large sa vol ratio
- oxygen + nutrients can diffuse directly and quickly in and out of cell
Why do larger organisms need a transport system?
- small sa vol ratio
- diffusion doesn’t occur quickly enough to sustain them
- larger organisms require organ systems w/ specialised adaptations to supply all their cells w nutrients + oxygen and collect waste (thru diffusion) to be excreted from the body
What is the function of the waxy cuticle?
- prevent water loss
What is the function of the upper epidermis?
Thin + transparent to allow more light through to chloroplasts
What is the function of the palisade cells?
- contain lots of chloroplasts to absorb more light
What is the function of the spongy layer?
Contains lots of air spaces to allow carbon dioxide to diffuse through leaf and increase the surface area
What is the function of the stomata?
- holes in the leaf to allow carbon dioxide to diffuse in and oxygen to diffuse out
What is the function of the guard cells
To open and close the holes in the leaf
To close to prevent water loss
What does the xylem do?
- transports water and dissolved minerals from the roots to the other parts of plant
What does the phloem do?
- transports sucrose + amino acids between leaves + other parts of plant
Describe the structure of xylem cells
- only transports from roots to shoots
- no cell wall so form continuous tubes
- hollow + strengthened through lignin
- xylem cells are dead
Describe the structure of phloem cells
- living
- sieve plates between cells where cell walls have partially broken down
- form continuous tubes
How are xylem and phloem arranged inside the root?
In vascular bundles
- xylem always on inside and phloem on outside
Explain how water is absorbed by root hair cells
- hair like extension increases the surface area to volume ratio
- thin walls (short distance)
- this increases rate of active transport (absorption of mineral ions)
- the cytoplasm of root hair cell lower water potential than soil
- water moves into root hair cell via osmosis
- higher of nitrates inside root hair cell than in soil
- nitrates move into root hair cell via active transport (+energy)
After the water is absorbed by the root hair cells, it moves into the root cortex cells. Explain how this happens.
There is a high water potential in root hair cell whereas there is a low water potential in root cortex cell, since water enters via osmosis (high -> low water potential)
