Biology 9700 · AS & A Level · Transport mechanisms
Transport mechanisms — practice question
Barlinka is a type of the common grapevine, Vitis vinifera. Its grapes are used both to make wine and to be sold as fruit. Using less water to irrigate grapevine plants, while still achieving a high crop yield, brings economic and ecological advantages.
The speed of sap movement through xylem vessels from roots to leaves can be taken as an estimate of transpiration rate. It also shows the rate of water uptake.
(a)[2]
The hydrogen bonding of water molecules is important in the movement of sap through xylem vessels. State the terms used to describe:
• water molecules joining together inside the xylem vessel
• water molecules attaching to the cellulose molecules in the lining of the xylem vessel
(b(i))[2]
The overall trend of the results in Fig. 4.1 is the same for all three Barlinka grapevines. Explain why this pattern is shared.
(b(ii))[2]
With reference to Fig. 4.1, explain why the results differ among grapevines 1, 2 and 3.
(b(iii))[1]
Suggest an explanation for the drop in xylem sap flow rate at time P in Fig. 4.1.
(b(iv))[2]
Outline how you would find the surface area of one side of a leaf.
Worked solution & mark scheme
This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Cohesion among water molecules.” …