Tropisms in plantsIB MYP Biology: Flashcards

Exam questions on Tropisms in plants

1. A sunflower seedling is grown in a pot on a classroom windowsill in Cape Town. After a week its shoot has bent towards the window, while its roots have grown downwards into the soil.
   Explain why it is an advantage to the seedling that its shoot grows towards the light.2 marks
2. Auxin is a plant hormone made in the tip of a growing shoot. In an experiment, light shines onto a shoot from one side only.
   Explain how the movement of auxin makes the shoot bend towards the light.2 marks
3. A student investigates whether cress seedlings respond to light. She grows 20 seedlings in each of two identical boxes kept at the same temperature and given the same amount of water. Box 1 has a small hole in one side, so light enters from one side only. Box 2 is lit equally from all sides. After five days she measures how far each shoot has bent from the vertical. The mean angle was 38 degrees in Box 1 and 3 degrees in Box 2.
   State a testable hypothesis for this investigation, with a scientific reason, and identify the independent and dependent variables.3 marks