A seedling is placed on its side in the dark. After two days, the root has grown downwards. Auxin has collected on the lower side of the root. Which statement explains why the root grows downwards?
Auxin stimulates cell elongation on the lower side of the root.
Auxin stimulates cell division on the upper side of the root.
Auxin inhibits cell elongation on the upper side of the root.
Auxin inhibits cell elongation on the lower side of the root.
84 exam-style questions on OCR GCSE Biology 3.2 Coordination and control – the endocrine system, covering 3.2.1 Principles of hormonal coordination and control, 3.2.2 Roles of thyroxine and adrenaline, 3.2.3 Hormones in human reproduction, 3.2.4 Interactions of reproductive hormones, 3.2.5 Hormones in contraception, 3.2.6 Hormones in reproductive technologies, 3.2.7 Plant hormones in growth and coordination, 3.2.8 Effects of plant hormones, and 3.2.9 Uses of plant hormones. Each one has a worked solution and a mark scheme showing where the marks go.