The Figure shows a seedling that has been placed on its side in the dark for two days. Auxin has collected on the lower side of both the shoot and the root. Figure [Image brief: a germinating seedling lying horizontally. The shoot on the right has curved upwards and the root on the left has curved downwards. Small dots on the lower side of both the shoot and the root are labelled 'auxin'. Labels: 'shoot', 'root', and an arrow pointing down labelled 'gravity'. No other labels.] Which statement explains why the shoot grows upwards but the root grows downwards?
Auxin inhibits cell elongation in both the shoot and the root.
Auxin stimulates cell elongation in the shoot but inhibits it in the root.
Auxin stimulates cell elongation in both the shoot and the root.
Auxin inhibits cell elongation in the shoot but stimulates it in 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.