Question

Take two glass jars and fill them with water. In next step, take two onion bulbs and place one on each jar. Placement of the onion bulbs on the mouth of each jar should be in such a way that the stem and root parts of each onion remain in contact with water (Figure 6). Observe the growth of roots in both the onion bulbs. Measure the length of roots on day 1, day 2 and day 3. However, on day 4 cut the root tips (i.e., up to 1 cm) in jar B. Observe the growth of roots in both jars for a few more days and record your observation in the following table:

Length of root	Day 1	Day 2	Day 3	Day 4	Day 5
1. Jar A
2. Jar B

From the above observations, answer the following questions:

1. Which of the jars has longer roots?
2. Do the roots continue growing even after you have removed their tips?
3. Why do the root tips stop growing in jar B after you have cut them?

Answer 1

1. Jar A has longer roots because its root tips remain intact. The apical meristem at each root tip produces new cells, allowing the roots to grow in length.
2. No. The roots in jar B stop elongating after their tips are cut off.
3. Cutting off the root tips removes the apical meristem, the actively dividing tissue responsible for growth in root length. Without it, the roots cannot continue to elongate.