Biology 9700 · AS & A Level · Transport mechanisms
Transport mechanisms — practice question
Once a leaf has just been produced, it is regarded as a sink for carbohydrate. As development continues, the leaf begins photosynthesis and then acts as a source of carbohydrates and other assimilates. Fig. 3.1 illustrates how the structure of plasmodesmata in the leaf alters as it grows.
(a)[2]
Suggest the benefit of complex plasmodesmata between cells in leaves.
(b)[4]
Assimilates are moved into phloem sieve tubes. Explain how assimilates in phloem sieve tubes travel from the veins of a mature leaf to sinks, such as flowers and fruits, elsewhere in the plant.
Worked solution & mark scheme
This 6-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Faster/more efficient movement/diffusion of assimilates through plasmodesmata via symplast pathway” …