Transport in Plants

Question 1

What are some adaptations of the phloem sieve tubes to enable mass flow?

Answer 1

• Elongated elements
• Sieve plates
• Little cytoplasm
• No nucleus

Question 2

Name the sugar molecule most commonly translated.

Answer 2

Sucrose

Question 3

Describe how assimilates are loaded into the phloem.

Answer 3

• Active transport of hydrogen ions creates concentration gradient.
• The hydrogen ions move back into companion cells via facilitated diffusion.
• Sucrose moves in with hydrogen ions by co-transport.
• Sucrose diffuses through the plasmodesmata into the sieve tube.

Question 4

Describe three steps a student should take when setting up the potometer to ensure that the
apparatus works correctly.

Answer 4

• Cut last 2-3 cm off the end at an angle.
• Check there is no air bubbles in the apparatus
• Check the apparatus is air tight
  Check the shoot is healthy

Question 5

What is the loss of water vapour from the aerial parts of a plant is known as?

Answer 5

Transpiration

Question 6

Explain why water loss from the leaves of a plant is unavoidable.

Answer 6

• Stomata open to allow gaseous exchange
• For photosynthesis which is essential for the plant to make sugars

Question 7

Explain why water loss from the leaves of a plant is unavoidable.

Answer 7

• Stomata open to allow gaseous exchange
• For photosynthesis which is essential for the plant to make sugars

Question 8

Name the type of plant adapted to reduce water loss from its leaves.

Answer 8

xerophyte

Question 9

Two adaptations of leaves that reduce evaporation.

Answer 9

• Thick cuticle that is impermeable
• Hairy leaves trap water vapour.
• Fewer stomata diffuses reduces diffusion
• Smaller leaves create a smaller SA.

Question 10

How does the structure of the xylem relate to its function?

Answer 10

• Long, continuous columns made of dead tissue –> transportation of water
• Pits —> allow water to move sideways between vessels
• Thickened with a tough substance —> provides structural support

Question 11

How does the structure of the phloem relate to its function?

Answer 11

Sieve tube elements –> transport sugars around the plant

Companion cells —> designed for active transport of sugars into tubes

Plasmodesmata —> allow flow of different substances between cytoplasm of different cells.