Question

In part A of a plant, sugars are actively transported into the phloem tissue. In part B, sugars are actively transported out of the phloem. Which way will the phloem sap move under these
conditions?

• A. From A to B
• B. From B to A
• C. First from A to B; then, once the pressure builds up, from B to A
• D. First from B to A; then, once the pressure builds up, from A to B

Answer 1

The correct option is A From A to B

Sap will flow from high to low pressure areas in the plant. Adding sugars to the sap causes water to enter the phloem, thus increasing pressure. Removing sugars causes water to leave the phloem, thereby reducing pressure. Hence, sap will move from A to B.