A student explored how roots and shoots respond to gravity in plant growth. The procedure was carried out like this: damp cotton wool was put into two Petri dishes; in each Petri dish, three bean seedlings were fixed onto the cotton wool; each seedling in a dish was set so that its roots faced a different direction; Petri dish 1 was left on its side and held in a fixed position; Petri dish 2 was left on its side and kept rotating continuously; both dishes were kept in the dark; both dishes remained in these conditions for two days; after two days, the seedlings were examined. Fig. 6.1 is a diagram of the apparatus. Fig. 6.2 shows the seedlings after two days.
(a(i))[1]
Describe the growth pattern of the bean roots and shoots in Petri dish 1, as shown in Fig. 6.2.
(a(ii))[1]
State the name of the growth responses shown by the bean roots and shoots.
(a(iii))[5]
Explain how auxin causes the difference in the pattern of growth seen in the shoots of seedlings B and E shown in Fig. 6.2.
(b(i))[1]
State one other environmental factor that affects germination.
(b(ii))[2]
Suggest why oxygen and water are needed for germination.
Worked solution & mark scheme
This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: “roots grow downward (positive gravitropism) or shoots grow upward (negative gravitropism)” …