Biology 9700 · AS & A Level · Control and coordination in plants
Control and coordination in plants — practice question
An investigation was done into how the plant growth regulator auxin affects apical dominance. The apical buds of 20 pea plants were removed and thrown away. The cut surfaces of 10 pea plants were covered with an inert paste containing auxin. The cut surfaces of the remaining 10 pea plants were covered with inert paste only. Another group of 10 pea plants had their apical buds left intact and were not covered with paste. This group acted as a control. The lengths of the side shoots on each of the three groups were measured at regular time intervals and mean values were worked out. The results are shown in Fig. 7.1.
(a)[3]
Explain why the side shoots become longer when the terminal buds are removed.
(b)[2]
Calculate the percentage difference, at 13 days, in the mean length of side shoots of plants treated with paste alone compared with the plants treated with paste and auxin. Give your answer to the nearest whole number. Show your working.
(c)[3]
Using data from Fig. 7.1, describe and explain the effect of auxin on the growth of side shoots.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “Auxin is produced by the apical bud” …