Question

Vein loading of sucrose into companion cell is

• A. Diffusion
• B. Active process
• C. Passive transport
• D. Turgor

Answer 1

The correct option is B Active process

By active transport, using energy in the form of ATP and a cotransport system, the sugar is moved to phloem sieve tube cells through the companion cells. This will create a hypertonic condition in the phloem near the source, and using the increased osmotic pressure in this area, the phloem sap will move to the low-pressure area near the sink. Finally, it will be taken out to sink also by active transport.

The passive transport which includes diffusion not possible because plants use energy in this form of transport described above.

The turgor pressure is the force within the cell exerted by water against the cell wall. But this won't help in the loading of sucrose into companion cells but rather might help in the osmotic transport.