Plant responses to the environment

This topic covers how plants respond to light and gravity through hormones, mainly auxins, and the tropisms that result. The 8 questions here are worth 13 marks in the November 2024 Paper 1 set. Of the 13 marks, 9 are for recalling facts and terms and 4 for explaining. Questions often describe a small experiment with shoots, tips and agar blocks.

The 2024 Diagnostic Report says candidates wrote "no growth" for a shoot with its tip cut off and replaced by plain agar, when there would be no upward growth but the lateral branches would still grow. In explanation questions they wrote about phototropism instead of the set-up given, and did not link auxins diffusing through the agar to cell division and elongation. They also added "positive" or "negative" to a tropism when the plain term, such as geotropism, was needed. Read the set-up carefully and name what changes.

Where marks are lost: in our words, from Department of Basic Education, NSC 2024 Diagnostic Report, Part 1 (Book 1).