NEET2023BotanyChapterActual
The function of companion cells 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 into and out of the sieve elements. In "source" tissue such as the 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.