Transpiration And translocation

Question 1

What are the Xylem and Phloem responsible for doing?

Answer 1

Transporting substance from the roots to the rest of the plant

Question 2

WHat substances does Xylem transport?

Answer 2

Water and mineral ions

Question 3

How are xylem vessels adapted to their function?

Answer 3

• Thick side walls and rings of lignin - form rigid tubes that will not burst/collapse (provide support)
• Dead cells- no cytoplasm, empty tube for water to flow through
• tiny pores - allows water and mineral ions to leave the xylem vessel
• The lack of cell walls between cells - water flow isn’t slowed down

Question 4

How do xylem vessels form long empty tubes

Answer 4

They die during their development and their top and bottom cell walls disintergrate

Question 5

What do phloem tubes transport around a plant?

Answer 5

Sugars, amino acids, cell sap

Question 6

How are phloem tubes adapted to transport substances around a plant?

Answer 6

Holes in the ends of the cell walls – allows liquids to flow from one Sieve sell to the other
– small amount of cytoplasm plus no nucleus – more room for central channel
– contains a pore through which sucrose solution can be pumped

Question 7

What is a sieve cell?

Answer 7

– A cell that has a large central channel for sugar to flow through
– form sieve tubes in the phloem tissue
– connected together by holes in the cell walls – allow sugar to neighbour sieve cell

Question 8

What is a companion cell?

Answer 8

• Alongside sieve cell
• Actively pump SUCROSE in and out of sieve cells
• Pimping IN increases pressure and causes sucrose to flow up/down where needed

Question 9

What is translocation?

Answer 9

The movement of sucrose (a sugar) through the phloem in a plant

Question 10

What is transpiration?

Answer 10

Water transport in plants is set up by evaporation of water from the leaves.
- Down a water potential gradient

Question 11

How does transpiration work (process)?

Answer 11

• Water flows into a root, up the stem and out of leaves
• Water moves up the XYLEM as a broken chain - forces of attraction between each molecule
• As water leaves the xylem, more get pulled up from the stem

Question 12

What are 4 factors that affect transpiration?

Answer 12

• WInd
• Humidity
• Temperature
• Light Intensity

Question 13

How does the wind affect transpiration?

Answer 13

The greater the wind = the greater the rate of transpiration

- Moving air removes water vapour, increasing the rate of Diffusion of water vapour from leaf

Question 14

How does humidity affect the rate of transpiration?

Answer 14

More humidity = less transpiration

- Diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air

Question 15

How does temperature affect the rate of transpiration?

Answer 15

Higher temperature = higher rate of transpiration

- Diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air

Question 16

How does light intensity affect the rate of transpiration?

Answer 16

Higher light intensity = higher rate of transpiration

• More photosynthesis
• The stomata open wider to allow more CO2 into the leaf for photosynthesis- more water can evaporate for transpiration

Question 17

What is used to measure the rate of transpiration?

Answer 17

Potometer

Question 18

How must valid results be obtained by using a potometer?

Answer 18

• Plant shoot must be fresh and healthy
• Plant shoot must be cut under water
• No air bubbles in apparatus
• Leaves must be dry

Question 19

Where can phloem tubes transport substances to?

Answer 19

Both up and down the plant