Topic F- Plant Transport

Question 0

Define osmosis in terms of water potential

Answer 0

• in osmosis water goes from a high water potential to low water potential down a water potential gradient, through a partially permutable membrane
• this process is passive ( no energy required)

Question 1

Describe the role of the phloem

Answer 1

Function:

a) transports sugar produced in leaves
b) divided tube
c) cells are alive
d) materials in the cell wall: cellulose
e) directions of the flow: up and down the stem to growing and storage tissues two ways

Question 2

Describe the role of the xylem

Answer 2

Function:

a) it absorbs water from the soil of its root hair cells
b) transports water and mineral ions
c) continuous tube
d) cells are dead
e) materials in the cell wall: cellulose+lignin
f) Directions of flow of substance:up the stem from the roots to the shoots and leaves ( one direction only)

Question 3

Define transpiration

Answer 3

Transpiration is the loss of water by evaporation from plants

Question 4

Explain how light intensity can effect the rate of transpiration

Answer 4

1. An increase in light intensity-> faster rate of photosynthesis
2. More photosynthesis means plant requires more CO2
3. /:\ plant open stomata further to allow CO2 to enter
4. With stomata open water vapor can escape in other directions
   End result: increase in light intensity->increase in transpiration

Question 5

Which environmental factors effect transpiration?

Answer 5

1. Temperature
2. Light intensity
3. Humidity
4. Wind speed

Question 7

Explain how humidity can effect the rage of transpiration

Answer 7

1. More humidity means more water vapor in the air
2. More water vapor outside the leaf means shallower concentration gradient
3. Shallow gradient means slower rate of diffusion
4. Slower rate-> less transpiration
   End result: inc. in humidity-> decrease in transpiration

Question 8

Describe experiments to investigate the role of environment factor in determine the rate of transpiration from a leafy shoot

Answer 8

1. A POTOMETER can be used to measure the rate of WATER UPTAKE
2. It does not measure transpiration
3. However because the water used in PHOTOSYNTHESIS and CELL TURGER the rate off water uptake can be used to APPROXIMATE transportation
4. To calculate the WATER LOSS we must use a MASS POTOMETER
   - the loss in mass from the apparatus is due to the loss of water

Question 9

Explain how water is absorbed by root hair cells

Answer 9

• Minerals go from LOW CONC. in soil to HIGHER CONC. in roots against a concentration gradient
• This requires energy from respiration /:\ roots need oxygen. This also requires protein channels to help transport the minerals

Question 10

Describe how temperature can effect the rate if transpiration

Answer 10

1. Increase in temp. -> increase in evaporation in the leaf
2. More evaporation in leaf->higher concentration of water vapor in leaf
3. Higher conc. of H2O vapor-> steeper concentration gradient /:\ faster rate diffusion
4. Higher temp. also means the air can hold more water vapor
   End result: increase in temp->increases rate of transpiration

Question 10

Explain how wind speed can effect the rate of transpiration

Answer 10

1. In still air a pocket of humid air collects around the stomata
2. This will reduce the rate of transpiration
3. However the wind will move the humid air and regain concentration gradient
   End result: increase in wind speed-> increase in transpiration

Question 11

Explain how the transpiration stream works

Answer 11

1. Water enters by osmosis
2. Water and mineral ions are carried up the xylem vessels to the rest of the plant
3. Carbon dioxide enters the leaf through the stomata by diffusion
4. In the leaf water joins with carbon dioxide to make sugar and oxygen
5. Some of the sugar is store as starch; some is carried to the rest of the plant
6. Oxygen passes through stomata and into the air by diffusion ( a useful waste product)
7. Sugar and amino acids are carried around the plant in the phloem tubes