Question

Translocation takes place using energy in the form of

• A. ATP
• B. NADPH
• C. FADH
• D. Glucose

Answer 1

The correct option is A ATP

Phloem carries sugars from sources where they are released (e.g. photosynthesising leaves) to sinks where they used (e.g. growing fruit, storage organs like roots which store the sugars as starch). This process is called translocation. The sugars cross the cell membranes of specialized parenchyma cells called companion cells. This cell-surface membrane can regulate the transport of the sugar and also drives it by actively, pumping sugar from the neighboring parenchyma cells into the phloem sieve tubes using membrane protein pumps that require cellular energy in the form of ATP. This pumping of sugars into the companion cell/sieve tube element creates an osmotic gradient, lowers the solute potential of the companion cell and hence lowers its water potential.

So, the correct answer is option A.