Transport in Plants- Xylem Flashcards
1
Q
what is the role of the xylem?
A
transports water and ions in a solution from the roots to the leaves
2
Q
outline the structure of the xylem
A
- long
- tube like
- formed from dead cells (vessel elements) at the end
- no end walls
- makes a continuous tube
2
Q
what process occurs in the xylem
A
transpiration
2
Q
outline the cohesion tension theory of water transport
A
- water evaporates from the leaves as the top of the xylem through transpiration
- creates tension, pulling more water into the leaf
- water molecules are cohesive so they stick together, moving the whole collumn of water upwards
- water then enters the stem through the roots
2
Q
define transpiration
A
the evaporation of water from a plants surface, down its concentration gradient, as there is a higher water potential in the leaves than the air outside
3
Q
name the four factors which affect the rate of transpiration
A
- light intensity
- temperature
- humidity
- wind
4
Q
an increase in humidity _____ the rate of respiration
A
lowers
5
Q
an increase in light intensity, temperature and wind _______ the rate of respiration
A
increases
6
Q
what would you use to measure transpiration rate?k
A
Potometer
7
Q
outline how you would estimate the rate of transpiration
A
- cut a shoot underwater, preventing air from entering the xylem
- cut at a slant to increase surface area available for water uptake
- assemble the potometer underwater, insert the plant shoot under the water
- keeping the capillery tube submerged in a beaker of water, remove the rest of the apparatus from the water
- check that apparatus is air and water tight
- dry the leaves
- remove end of the capillary tube until water bubble has formed then place it back in the beaker
- record the starting position of the bubble
- record the distance travelled by the airbubble which acts as an estimation of rate of transpiration, start the stopwatch
