Transport of water in plants.

?
  • Created by: rachel
  • Created on: 13-02-13 10:54
Which figure shows the highest water potential? -400, -500 or -300 kPa
-300.
1 of 32
What can decrease the water potential in a cell?
- If they have more solutes in them than other cells. - If they are loosing more water through evaporation to the air than another cell is.
2 of 32
What is the symbol for water potential?
A trident.
3 of 32
Why would water move from cell P (water potential of -300kPa) to cell Q (water potential of -400kPa)?
Because -300 kPa is greater then -400 kPa, water moves from a higher water potential (P) to a lower water potential (Q).
4 of 32
From this diagram of three mesophyll cells (pg. 58) state the direction of movement between the cells.
Cell P - water moves to cells Q & R because they are of a lower water potential. Cell Q - water moves to cell R because cell R has a lower water potential.
5 of 32
Where is most of the water absorbed in plants lost to?
The atmosphere, during transpiration.
6 of 32
Water is absorbed by ______ hair cells & passes across the _____ of the root, through the _________ & into the ______ in the central region. From here it travels inside the xylem vessels until it reaches the ______ where it may reach cells and be use
root, cortex, endodermis, xylem, leaves.
7 of 32
What can water be used to do, within a plant?
- can be used as a raw material for photosynthesis. - enter a vacuole to give it turgidity and help with support etc. - Pass to the cell wall & evaporate into the air spaces in the leaf.
8 of 32
Water vapour that evaporates from cell walls may diffuse through the ______ into the atmosphere outside the leaf.
Stomata.
9 of 32
When water travels across the cortex of the root and across the leaf, what are the two main pathways it may follow? Briefly explain these pathways.
The apoplast pathway - along cell walls. The symplast pathway - from cell to cell through the plasmodesmata.
10 of 32
Which pathway would most of the water probably follow and why?
The apoplast pathway because it's the pathway with the least resistance.
11 of 32
Water always moves ____ a concentration gradient.
Down.
12 of 32
What is the endodermis?
A layer of cells that have impermeable material between the cell walls.
13 of 32
How is the endodermis a barrier to the apoplast pathway?
Water has to travel through cells to get into the xylem.
14 of 32
What is the function of the endodermis?
To select ions to pump from cortex into the xylem and then transport to rest of plant.
15 of 32
What is the transpiration pull?
The force that draws water up through xylem vessels.
16 of 32
Where does water evaporate from, in a plant?
From the cell surfaces inside a leaf.
17 of 32
What happens to the air spaces inside the leaves when water evaporates fro the cell surfaces inside the leaf? What would then happen if the stomata were open?
The air spaces in the leaf become fully saturated with water vapour. If the stomata were open at this stage, the water vapour would escape by diffusion.
18 of 32
Transpiration is the combined effect of _______ from the internal surfaces of leaves and the _____ of water vapour out of the leaves.
Evaporation, Diffusion.
19 of 32
Why does water move through plants?
Because of cohesive tension - cohesive forces between water molecules and the adhesive forces between water & the cellulose in cell walls.
20 of 32
Explain how temperature can effect the rate of transpiration occurring
On hot days, rate of evaporation > & air holds more water. Increasing temperature increases rate of transpiration.
21 of 32
Explain how humidity can effect the rate of transpiration occurring
On very humid days, atmosphere may hold as much water as air inside leaves. This means there is little/no gradient for the diffusion of water vapour. Increasing humidity, decreases rate of transpiration.
22 of 32
Explain how wind speed can effect the rate of transpiration occurring.
On windy days, water vapour molecules are blown away from the leaf surface as soon as they pass through from the stomata. Increasing air speed tends to increase the rate of transpiration.
23 of 32
Explain how light intensity can effect the rate of transpiration occurring.
Stomata open during daylight hours to obtain carbon dioxide for photosynthesis. When stomata are open, water vapour diffuses out of leaf down the diffusion gradient. At night - no photosyn. so close stomata to conserve H20. Light intensity > Transp >
24 of 32
How are some desert plants different to english plants in terms of opening and closing their stomata?
Some desert plants open their stomata at night to take in CO2 and close them during the day to conserve water.
25 of 32
How can you measure the rates of transpiration?
Using a potometer - however you must put potometer on a balance. You can measure transpiration rate by measuring loss in mass.
26 of 32
What can a potometer measure as well as transpiration?
It measures the rate at which lefty shoots cut from plants absorb water (water uptake) You measure the water uptake by following the movement of the bubble of air.
27 of 32
What are some of the precautions you should take when setting up a potometer.
- Leafy shoot cut under water & placed in potometer under H20 so air doesn't enter xylem vessels & block them. - Leafy shoot should be left in poto. for some time to adjust before readings are taken. - Conditions around shoot should remain constant.
28 of 32
What should you always do to increase reliability of results when using a potometer.
Do repeats.
29 of 32
when investigating one factor e.g. temperature, in a potometer, what should be kept contant?
The other conditions.
30 of 32
What form are the readings given from a potometer?
Distance travelled (of air bubble) in a certain period of time.
31 of 32
Calculate the volume of water that had been absorbed (volume of cylinder = pie squared x h [distance travelled by air bubble] if you know you have a tube with a radius or 1mm, if the bubble travels 20mm in 15 minutes
Volume of a cylinder - 3.14 x 1 x 20 = 62.8 mm3. Rate of water uptake - 62.8 / 15 = 4..2mm3min-1 (to the nearest 0.1mm3min-1)
32 of 32

Other cards in this set

Card 2

Front

What can decrease the water potential in a cell?

Back

- If they have more solutes in them than other cells. - If they are loosing more water through evaporation to the air than another cell is.

Card 3

Front

What is the symbol for water potential?

Back

Preview of the front of card 3

Card 4

Front

Why would water move from cell P (water potential of -300kPa) to cell Q (water potential of -400kPa)?

Back

Preview of the front of card 4

Card 5

Front

From this diagram of three mesophyll cells (pg. 58) state the direction of movement between the cells.

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

Plants
See all Biology resources »See all Biological molecules, organic chemistry and biochemistry resources »