Question

As shown in the figure, place an onion on each gas jar in such a way that its base (roots) will remain dipped in water. Measure and record the length of the roots of both onions on the first, second and third day. On the fourth day, cut off 1 cm of the roots of the onion in flask B Measure the length of the roots of both onions for the next five days and record your observations in the following table.

Changes in roots of onion

Length (cm)	Day 1	Day 2	Day 3	Day 4	Day 5
Flask A
Flask B

(a) Which onion has longer roots? Why?

(b) Why did the roots of the onion in jar B stop growing?

Answer 1

(a) The onion in jar has longer roots as it continues to grow due to the presence of meristematic tissue at root tip which had dividing cells.

(b) The roots of onion in jar B stopped growing as the meristematic tissue present in the root tips were cut off.