Question

Which of the following is not correct with respect to mass flow hypothesis?

• A. Loading of phloem sets up a water potential gradient that facilitates the mass movement in phloem.
• B. The sugar which is transported in phloem sieve.
• C. The sugar is moved bidirectionally
• D. As hydrostatic pressure in phloem sieve tube increases, pressure flow stops and sap accumulates in phloem.

Answer 1

The correct option is D As hydrostatic pressure in phloem sieve tube increases, pressure flow stops and sap accumulates in phloem.

According to the mass flow hypothesis, the loading of phloem or accumulation of sugars sets up a water potential which causes the water from nearby xylem cells to enter the phloem tissue and a turgor pressure is developed which causes mass movement.

The flow of sugar is through sieve tubes and the flow is many a time bidirectional.

Due to hydrostatic pressure, pressure flow increases and the phloem sap starts moving.

So the correct answer is 'As hydrostatic pressure in phloem sieve tubes increases, pressure flow stops and sap accumulates in phloem'.