Question

You observe that a plant with some type of mutation does not have a phototropic response. What is a possible explanation for this observation? The proton pumps are not able to move to the shady side of the plant. O Auxin is unable to bind to the receptor in the nucleus to release the repressor that is preventing transcription of more proton pumps. The auxin transporters are unable to move to the shady side of the plant cell. The auxin transporters are unable to move to the sunny side of the plant cell.

Answer 1

To answer this let's analyze first how the phottrophic response works. We have a plant's tip that is receiving light, when light falls from one side, auxins inside the tip of the plant travel to the shady part and promote its elongation, leading to a curvature towards the light source. The molecular action of auxin to the shady part tissue beggins with an activation of proton pumps.

The first answer is not correct, as the pumps are not the ones moving, they are already in every cell, but they have to get activated by a higher auxin concentration.

Second answer is not correct, the mechanism is not about more pump transcription event, proton pumps are already in place.

Fourth answer is not correct, auxins need to move to the shady part to elongate its tissue, not the sunny side.

The answer is the third option: Auxins transporters are unable to move to the shady side of the plant