Transpiration And Translocation

Question 1

What are 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’s ill 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

Sieve tube adaptations (phloem)?

Answer 6

• Specialised for transport
• No nuclei
• Each sieve tube had a perforated end, connecting its cytoplasm to the next tube

Question 7

What is a sieve cell?

Answer 7

• Cell that have 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

Companion cell adaptations (phloem)?

Answer 8

• Transport of substances in the phloem = require energy

- One or more companion cells attached to each sieve tube - provide energy

Question 9

What is a companion cell?

Answer 9

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

Question 10

What is translocation?

Answer 10

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

Question 11

What is transpiration?

Answer 11

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

Question 12

How does transpiration work (process)?

Answer 12

• 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 13

What are the 4 factors which affect transpiration?

Answer 13

• Wind
• Humidity
• Temperature
• Light Intensity

Question 14

How does wind affect transpiration?

Answer 14

The greater the wind = greater rate of transpiration

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

Question 15

How does humidity affect the rate of transpiration?

Answer 15

More humidity = less transpiration

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

Question 16

How does temperature affect the rate of transpiration?

Answer 16

Higher temperature = higher rate of transpiration

- Evaporation and Diffusion are faster at higher temperatures

Question 17

How does light intensity affect the rate of transpiration?

Answer 17

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 18

What is used to measure the rate of transpiration?

Answer 18

Potometer

Question 19

How must valid result be obtained by using a potometer?

Answer 19

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

Question 20

Where can phloem tubes transport substances to?

Answer 20

Both up and down the plant.