OBJECTIVES
1. The curvature movement of plants in response to the stimulus of water is called
A. hydrotropism.
B. geotropism.
C. phototropism.
D. thigmotropism.
The diagrams below are illustrations of an experimental set-up to demonstrate a type of tropic response in
plants. Study them and answer questions 2 & 3
2. The type of response demonstrated is
A. phototropism.
B. geotropism.
C. hydrotropism.
D. thigmotropism.
3. The conclusion drawn from the experiment is that
A. shoots of plants, are negatively thigmotropic.
B. shoots of plants are negatively geotropic.
C. leaves of plants are positively phototropic.
D. roots of plants are positively hydrotropic.
4. Which of these instruments can be used to perform an experiment on geotropism?
A. Potometer.
B. Cup anemometer.
C. Klinostat.
D. Kymograph.
5. Growing radicles of seedlings are
A. negatively phototropic.
B. positively phototropic.
C. negatively geotropic.
D. negatively hydrotropic.
THEORY
1. (a) In a tabular form, distinguish between tropic movements and nastic movements. (b) Explain how light brings about tropic movement in the stem and root of a flowering plant
2. Describe an experiment to demonstrate the effect of gravity on the roots of plants
3. (a) State two differences between tactic and nastic movements in plants (b) Give two examples each of organisms that show (i) tactic movement (ii) nastic movement
4. What would be observed when a growing seedling is placed horizontally?
5. Describe an experiment to show that plant roots respond positively to gravity
6. (a) Define tropic and nastic movements, (b) Give two examples of tropism. (c) List four differences between tropic and nastic movements.
7. (a) List three organs of a higher plant that can respond to stimulus (b) What is tactic movement? (c) Explain the following terms, giving one example in each case: (i) Phototaxis (ii) Hydrotaxis (iii) Chemotax
8. (a) What is irritability (b) Complete the table by stating the type of response elicited by each of the given actions.
| Action | Type of response |
| Euglena moving towards source of light | |
| Opening and closing of mimosa plant leaves | |
| Mosquitoes avoiding repellants | |
| Earthworm moving away from light | |
| Sperm cell moving towards chemical substances of an ovum | |
| Four o’ Clock plant opening at 4:00pm | |
| Shoot of bean seedling growing towards sunlight |
