Xylem Flashcards
1
Q
transpiration
A
the evaporation of water from the leaves through the stomata
2
Q
cohesion
A
the tendancy of water molecules to stick together because they are polar
3
Q
what does xylem transport?
A
water and dissolved minerals
4
Q
what direction does xylem move water?
A
up
5
Q
describe the structure of xylem
A
- a hollow tube of dead cells
- there are no cell walls between cells
6
Q
describe the cohesion-tension theory
A
- water is lost via transpiration through stomata
- this creates a low pressure at the top of the xylem
- because water molecules are cohesive and stick together due to being polar
- water is pulled up the xylem in an unbroken chain creating tension
- this causes water to be sucked up to the leaves
7
Q
how does temperature affect the rate of transpiration?
A
- higher temperatures increase the amount of evaporation of water through stomata
- and the rate of transpiration increases
8
Q
how does light affect the rate of transpiration?
A
- more light increases the amount of stomata open
- because more photosynthesis takes place
- this means the rate of transpiration increases
9
Q
how does humidity affect the rate of transpiration?
A
- decreases the vapour gradient
- decreases rate of transpiration
10
Q
how do dry/windy conditons affect the rate of transpiration?
A
- increases the vapour gradient
- increases rate of transpiration
