Biology 9700 · AS & A Level · Structure of transport tissues
Structure of transport tissues — practice question
Leaf veins contain transport tissues. Fig. 2.1 is a drawing based on an electron micrograph of a transverse section through the transport tissue in a leaf vein. The cells labelled A are altered companion cells called phloem transfer cells. Transfer cells move sucrose and other assimilates from mesophyll cells, B, into the phloem sieve tube element, C.
(main)
Use Fig. 2.1 together with the details given about the transport tissue in a leaf vein.
(a)[5]
State the roles of the mesophyll cells, B, and sieve tube element, C, and Explain how each structure is adapted for its role.
cell B - role
adaptation
cell C - role
adaptation
(b)[3]
The cell walls of the transfer cells, A, in Fig. 2.1 are folded inwards.
Explain the benefits of these wall infoldings for moving sucrose from mesophyll cells to phloem sieve tubes.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Photosynthesis is the light-energy-driven conversion of carbon dioxide into sugars” …