Question

Rohan set up an experiment with germinating bean seeds. He fixed the seeds on a wire mesh with moist sawdust placed below them. At the start, the radicles grow downward and the plumules upward. After a few days though, he noticed that the radicles began bending towards the moist sawdust instead of simply going straight down.

1. Name two types of tropic movements shown by the radicles in this experiment.
2. What stimuli are responsible for these movements?
3. Which one of the stimuli mentioned by you above in (b) is more effective for the growth of the radicles in this experiment?
4. Why do the plumules continue to grow upwards even after the radicles bend?

Answer 1

1. Two types of tropic movements shown by the radicles in this experiment are geotropism and hydrotropism.
2. Stimuli responsible for these movements are gravity and moisture.
3. Moisture is more effective for the growth of the radicles in this experiment.
4. The plumules continue to grow upwards because they are negatively geotropic, that is, they grow in the direction opposite to gravity.