Question

Assertion: Phloem transports solutes towards the sink.
Reason: Turgor pressure helps in the movement of sap through the phloem.

• A. A is correct and R is the correct explanation of A
• B. Both A and R are correct. But R is not the correct explanation of A
• C. Only A is correct
• D. Both A and R are incorrect

Answer 1

The correct option is A A is correct and R is the correct explanation of A

Glucose produced by the photosynthetically active parts of the plant, which is converted to sucrose and translocated to the different parts of the plant through the phloem. Phloem tissue is composed of sieve tube cells, which form long columns with holes in their end walls called sieve plates. Cytoplasmic strands pass through the holes in the sieve plates forming continuous filaments.

The entry of sucrose in the cells increases the solute concentration in the phloem and decreases the water potential. The elevated solute concentration prompts water to flow from the xylem into the phloem by osmosis.

As water flows from xylem to phloem, water potential and turgor pressure increases in the sieve tubes cell and the phloem sap i.e. water and solutes, will move to areas of lower pressure through the perforated sieve plate.

The positive pressure generated drives the movement of phloem sap down the pressure gradient, transporting the solutes away from the source and consequently towards the sink.