Given below is an experimental setup to demonstrate a particular tropic movement in germinating seeds (seeds fixed to a perforated trough of moist sawdust). Study the diagram and answer the questions that follow: Given below is an experimental setup to demonstrate a particular tropic movement in germinating seeds (seeds fixed to a perforated trough of moist sawdust). Study the diagram and answer the questions that follow:
Name the tropic movement shown by part 1.
Topic: Tropic movement of the radicle
Answer
The radicle shows POSITIVE GEOTROPISM (growth towards gravity) and POSITIVE HYDROTROPISM (growth towards water).
Use the words POSITIVE and NEGATIVE — they are what earn the mark. POSITIVE means growth TOWARDS the stimulus, NEGATIVE means AWAY from it.
The radicle is positive to BOTH gravity and water, and in this apparatus both stimuli are present — gravity pulling down and moist sawdust supplying water. That is what sets up part (iii).
The plumule shows the reverse: NEGATIVE geotropism and POSITIVE phototropism.
WHY EACH ORGAN BEHAVES SO: the root must reach water and anchor the plant; the shoot must reach light for photosynthesis. Each grows in the direction that serves its function.