Indole-3-acetic acid (IAA) is a common auxin that affects the growth of plants. An investigation was done to determine the effect of different concentrations of IAA on the growth of young roots. The results of this investigation are shown in the graph.
State the conclusion that can be drawn from these results.
A group of students investigated the effect of removing the root tip on the gravitropic response of a radicle.
The students had two groups of plants, each containing five seedlings, that were germinated at the same time and under the same conditions. Group 1 had the end 2 mm of the root tip removed, while Group 2 was left intact. All ten seedlings were laid flat and the position of each root tip was marked on a sheet of paper that was placed beneath the seedlings. After five hours the new position of the root tips were marked on the paper and the angle of bending was measured. An upward-bending root was recorded as a negative value and a downward-bending root was recorded as a positive value.
The results are displayed in the table.
Plant seedling
Root bending / degrees
Group 1 (without root tip)
Group 2 (with root tip)
1
0
42
2
-3
39
3
0
37
4
0
40
5
-2
35
Mean
-1
39
Suggest an explanation for the results shown in the table above.
