Question

(short writing) Phototropism is a phenomenon observed in plants. Phototropism is best described as a plant’s response to light. Auxin is a hormone and signaling molecule found in plants that promotes cell elongation. It is observed that auxin concentrations are lower in the parts of the plant that are closest to light. Auxin concentrations are higher in the parts of a plant that are in the shade.

Answer the following in the space provided.
Describe phototropism using what you know about signal transduction. Start with auxin as a signaling molecule.
Explain how altering the receptor would affect the signaling pathway.
Predict how a plant would respond to exposure to light on all sides of a growing stem.
Provide reasoning and justification for your prediction.

Answer 1

1) a) Auxin moves to the darker side of the plant, causing the cells there to grow larger than corresponding cells on the lighter side of the plant. This produces a curving of the plant stem tip toward the light, a plant movement known as phototropism. Auxin also plays a role in maintaining apical dominance.