Plants respond to light, gravity, touch and water, and the chapter asks you to name, explain and predict those responses. The four lessons below build from vocabulary to evidence.
This chapter is part of SPM Biology, and it pairs with coordination and response in animals for comparison.
How do the four lessons connect?
Each lesson adds one layer to the same idea.
- Distinguishing tropic and nastic responses sets out the two types and how to tell them apart.
- Explaining growth responses to stimuli links auxin to bending in shoots and roots.
- Interpreting plant-hormone investigations teaches you to read tip-removal and agar-block experiments.
- Predicting responses using supplied evidence uses the evidence to forecast a new result.
What does one windowsill seedling show?
A seedling sits on a windowsill with the sun coming from the left. After two days its shoot curves to the left, and this is a tropic response, because the bending direction follows the direction of the light. The auxin in the shoot moves to the shaded side, where it makes cells elongate more, so the shaded side grows longer and the shoot bends toward the light.
The same seedling’s roots grow downward whatever the light does, which is a response to gravity. Next to it, a touch-sensitive plant folds its leaflets when brushed, and that movement does not depend on the direction of the touch. One windowsill contains tropic and nastic responses and a hormone explanation.
Who should start where?
If the two types of response blur together, begin with lesson one. If you know the terms but cannot explain the bending, go to lesson two. If experiment diagrams confuse you, start at lesson three, and if you can read them but cannot forecast results, lesson four is the quickest fix.
Test yourself with the plant responses practice set.
When does extra help make sense?
Plant response answers usually fail on one missing link, such as which side has more auxin. A teacher who reads your answer line by line can spot the missing link and show how to build the chain from stimulus to result.
If that sounds useful, see online one-to-one Biology tuition and mention plant responses when you enquire.