NTA Abhyas NEET2020BotanyTransport in PlantsPractice
The function of nucleated cells in phloem is to _____
Options
- Aprovide energy to sieve elements for active transport.
- Bprovide water to phloem.
- Cload sucrose into sieve elements by passive transport.
- Dload sucrose into sieve elements by active transport.
Correct answer
D. load sucrose into sieve elements by active transport.
Step-by-step solution
Companion cells move sugar and amino acids in and out of the sieve elements. In "source" tissue such as leaf, companion cells use transmembrane proteins to take up sugar and amino acids by active transport. Movement of sugars in the phloem begins at the source, where sugars are loaded (actively transported) into a sieve tube. Loading sets up a water potential gradient that facilitates the movement of sugar.