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?