Plant Biology Flashcards
1
Q
What is the function of the xylem?
A
- Move water from the roots to the leaves
2
Q
What is the function of the phloem?
A
Move nutrients around the plant
3
Q
What is the difference in the structure between phloem and xylem
A
- Xylem vessels are dead and open ended made from lots of cellulose for strength
- The phloem cells are alive and have partially permeable membranes
4
Q
What is transpiration?
A
The diffusion and evaporation of water from the underside of leaves through stomata
5
Q
What 4 factors affect the rate of transpiration - explain why
A
- Temperature - The warmer the air, the faster the evaporation
- Light - Stoma are open to allow oxygen and carbon dioxide movement, therefore more water is lost
- Wind - The more wind, the faster the transpiration because there is a higher concentration gradient that is maintained by water vapour quickly moving away
- Humidity - More water around the leaves slows down transpiration as there is a smaller concentration gradient
6
Q
How does the structure of leaves aid there function?
A
- Waxy cuticle - keeps the leaf waterproof on the top surface to prevent the loss of water
- upper epidermis - thin to allow as much light as possible through to the palisade cells
- palisade cells - full of chloroplast because they are clots to the top for photosynthesise
- spongy mesophyll there are space around the cells to allow the moment of air and water around the leaf
- lower epidermis - contains the guard cells
- guard cells - swell to open the stomata In light, guard cells take up water by osmosis because the concentration of potassium is high, so become turgid. Because their inner walls are rigid they are pulled apart, opening the pore.
7
Q
Why does the increase of potassium in guard cells cause water to also move into them?
A
As potassium increases, more water moves in to balance the water potential between the guard cell and its surroundings
