Discussion
In polymer-traping model of phloem loading, raffinose and stachyose are synthesized in the.......
Answer: C
In the polymer-trapping model, raffinose and stachyose are made in the intermediary cell.
In plants such as cucurbits that load phloem symplastically, sucrose made in the mesophyll diffuses through plasmodesmata into specialised companion cells called intermediary cells. There it is combined with galactose to form the larger sugars raffinose and stachyose. These are too large to diffuse back through the narrow plasmodesmata towards the bundle sheath but can pass on into the sieve elements, so they are trapped in the phloem and concentrated there.
The mesophyll and bundle sheath supply sucrose, not the polymers, and the sieve element transports them but does not synthesise them.
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