Maize seeds were fixed to a board and given light from every direction. The board was set inside a clinostat, which kept the board turning. As the seeds germinated and the roots lengthened, the board continued to rotate without interruption. Fig. 6.1 shows the apparatus and the outcome after 5 days. The diagram is labelled clinostat, board, root, and a maize seed attached to the board.
(a(i))[5]
Complete the statements below to account for the root growth in Fig. 6.1.
Auxin is made in shoot and root [BLANK]. It moves down the root by [BLANK]. As the clinostat turns, [BLANK] acts equally on every side of the root. This makes auxin distribution in the root [BLANK]. Auxin triggers cell [BLANK], so the roots extend horizontally.
(a(ii))[1]
Predict how the growth of the germinating maize seeds shown in Fig. 6.1 will change.
(a(iii))[1]
State the term for the tropic response to light.
(b)[3]
State and explain how the cells would be expected to look.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “shoot and root tips” …