7. Transport in plants
A section of Biology, 9700
Listing 10 of 457 questions
With reference to the structure of a leaf, explain the difference between evaporation and transpiration. Apple, Pyrus malus, sour cherry, Prunus cerasus, and peach, Prunus persica, are dicotyledonous trees that are of importance to commercial growers for the fruit that they produce. A student chose a small area of land where all three species of fruit tree were growing. Leaf samples were removed and, using a microscope, the mean number of stomata per square millimetre was estimated for each species. The rate of transpiration of each species was then measured on each of three separate occasions. The student performed the investigation outside where the trees were located and recorded the weather conditions on each day. The mean transpiration rate was calculated per unit area of leaf. The results are shown in Table 3.1. Table 3.1 fruit tree mean number of stomata / mm–2 mean transpiration rate / cm3 h–1 hot dry day warm dry day warm rainy day apple 0.19 0.35 0.21 sour cherry 0.09 0.28 0.25 peach 0.03 0.08 0.07 With reference to Table 3.1, describe and explain the results of the investigation. The mean transpiration rate of each species was calculated over a 24 hour period. Describe how the transpiration rate during the night would differ from the transpiration rate during the day. Explain your answer. Suggest which of the three species of fruit tree has been described as ‘drought-resistant’ and would be economical to grow in areas where water is scarce. Many fruits are thought to have beneficial health effects. Sour cherries and peaches may contribute to improved health for tobacco smokers. Read the following statements. For each, explain how the fruit contributes to protecting smokers from smoking-related diseases. Glutathione is a protein known to be involved in the repair of damaged DNA. Regularly eating sour cherries increases the level of glutathione in the body. A diet rich in peaches can help reduce inflammation of the bronchi and bronchioles.
9700_s12_qp_22
THEORY
2012
Paper 2, Variant 2
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