Mass Transport In Plants (4.11)

Question 1

Describe the process involved in loading and unloading glucose/sucrose from the phloem

Answer 1

Sucrose is released from the source into companion cells of the phloem. Through translocation sucrose moves down the phloem towards a sink where it will then diffuse into the sink cell out of the phloem.

Question 2

Explain why companion/transfer cells have a large number of mitochondria compared to the phloem cells

Answer 2

Once the sucrose reaches the phloem tissue in a source, it needs to be actively transported into the companion cells and sieve tube members. This process does require energy, and this is why the companion cells must have many mitochondria to release this energy through cellular respiration.

Question 3

Explain how water moves up the xylem

Answer 3

Water molecules have a dipolar nature, with partially charged oxygen and hydrogen. Therefore water holds certain properties such as cohesion and adhesion.