One example of chemical control and co-ordination in plants is in the breakdown of food reserves during the germination of cereal grains, such as wheat. (a) Fig. 3.1 is a diagram of a grain of wheat. The numbered arrows indicate the sequence of events that occurs after the uptake of water by the grain of wheat. [Figure 3.1]

1. (a)(i)Name structures A, B and C, shown in Fig. 3.1. A B C[3]
2. (a)(ii)With reference to the three numbered arrows in Fig. 3.1, describe the sequence of events that follows the uptake of water by the grain of wheat.[6]
3. (b)Growth in plants occurs in areas such as shoot and root tips. Growth occurs by cell division and cell elongation. Fig. 3.2 shows the effect of the plant growth regulator auxin on mean cell length in the shoot tips of wheat seedlings. [Figure 3.2]
4. (b)(i)With reference to Fig. 3.2, calculate the overall rate of increase in mean cell length over the time period shown.[2]
5. (b)(ii)The pH of the cell walls decreased after the application of auxin. Outline the events that occurred to cause this decrease in pH.[2]
6. (b)(iii)Explain the increase in the length of the cells following the decrease in pH of the cell walls.[3]

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