Plant responses
Method overview
Place similar seedlings in controlled containers. Expose groups to directional light, uniform light/darkness or altered gravity orientation. Measure growth angle/length after a fixed time and compare controls.
Apparatus set-up
Diagramgerminating seedlings; Petri dishes; cotton wool; light box; clinostat or directional light; ruler/protractor
Independent variable
direction of light or gravity
Dependent variable
growth direction, angle or length
Control variables
seedling species/age; water; temperature; time; initial orientation; light intensity except direction
Apparatus
germinating seedlings; Petri dishes; cotton wool; light box; clinostat or directional light; ruler/protractor
Safety
Handle seedlings and glassware carefully; wash hands after biological material.
Scientific rationale
A control distinguishes directional response from normal growth; rotating a clinostat averages the gravity stimulus; auxin redistribution changes cell elongation.