Exchange and Transport in Plants

Question 1

Functions of the Xylem

Answer 1

• Carries dissolved minerals and water UP the plant
• Food storage (sclerenchyma)
• Structural support

Question 2

Functions of Phloem

Answer 2

• Transport sugars (sucrose)
• From leaf to rest of plant

Question 3

4 types xylem tissue in a plant

Answer 3

• Tracheid (pits cells)
• Vessel elements (large with lignin strengthened walls
• Xylem Parenchyma
• Sclerenchyma

Question 4

Structural features of Xylem

Answer 4

• Lignified cell wall (strength, withstands hydrostatic pressure so vessels do not collapse, impermeable to water)
• No end plates, (constant mass flow, cohesive forces aren’t impeded)
• No protoplasm, (so little resistance to transpiration stream)
• Pits in walls (allows continual flow of water in case of air bubbles)
• Small diameter of vessels (Prevents water column from breaking and assist with capillary action)

Question 5

Main types of cell in Phloem

Answer 5

• Sieve tube elements
• Companion cells
• Parenchyma for storage
• Strengthening fibres

Question 6

Structure of Phloem

Answer 6

• Sieve plates (have sieve pores, allow continuous movement)
• Cellulose cell wall (strengthens wall to withstand hydrostatic pressure moving assimilates)
• No nucleus, vacuole or ribosomes, (maximises space for translocation)
• Thin Cytoplasm (reduces friction to facilitate movement of assimilates)