Translocation

Question 1

Mass flow hypothesis 1

Answer 1

Active transport loads solutes into sieve tubes of the phloem at the source. This lowers water potential in the sieve tubes so the water enters via osmosis from xylem and companion cells. This creates high pressure in the sieve tubes at the source end

Question 2

Mass flow hypothesis 2

Answer 2

At the sink end solutes are removed. This increases the water potential inside the sieve tubes so water leaves the tubes by osmosis. This lowers the pressure inside the sieve tubes. This lowers the pressure inside the sieve tubes.

Question 3

Mass flow hypothesis 3

Answer 3

This creates a pressure gradient from source end and sink end. This cause solutes to move along sieve tubes when they’re needed.