Define the term tropism.
Organisms can only survive if they are able to respond to changes in their environment.
Describe how the plant growth factor, indoleacetic acid (IAA), allows plants to respond to light stimuli from their surroundings.
IAA has the opposite effect on the cells in plant roots. The growth factor is actively transported to the bottom region of the root tip where amyloplasts are located, as shown in Figure 1.
Figure 1
Explain why the amyloplasts are located at the bottom of the root tip.
In an investigation to test the effect of IAA on shoot growth in seedlings, three different environments were set up:
Group A = Shoot with the tip removed.
Group B = Shoot has been covered in a light proof container.
Group C = Shoot was grown under a directional light source.
Figure 2
Complete the diagram in Figure 2 to show what you would expect to see in the shoot which was grown under a directional light source. Remember to label the IAA molecules on your diagram.
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