Turn over 25 9 Water moves through xylem vessels in a plant during transpiration. Phloem tissue is responsible for transport of organic materials such as sucrose. (a) Compare and contrast the structure of xylem tissue and phloem tissue. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (b) A student used the potometer shown in the diagram to investigate the rate of water uptake in a leafy shoot. cut shoot reservoir scale air bubble beaker of water capillary tube The student investigated the effect of a combination of environmental conditions on the rate of water uptake. 26 The table shows the results of this investigation. Conditions Distance moved by the bubble in 5 minutes / cm Trial 1 Trial 2 Trial 3 Trial 4 Trial 5 Mean Still air, in light 2.4 2.2 2.2 2.2 2.1 2.2 Moving air, in light 6.5 6.7 6.4 6.2 6.3 6.4 Still air, in dark 0.9 0.4 0.0 0.0 0.0 0.3 Moving air, in dark 1.7 0.8 0.0 0.0 0.0 0.5 (i) The internal diameter of the capillary tubing is 0.3 mm. The volume of a cylinder is calculated using the formula πr2h Calculate the mean rate of water uptake for the shoot in moving air, in the light. Give your answer in mm3 min–1 to two significant figures. (3) Answer .............................................................. mm3 min–1 Turn over 27 (ii) Analyse the data to explain the results of this investigation. (3) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (iii) Describe how this investigation could be modified to make a valid comparison of water loss from the upper and lower surfaces of the leaves. (4) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (Total for Question 9 = 13 marks) 28 BLANK PAGE