Evaluate the following assertions about phototropism. Select True or False for each statement. T/F Cells on the illuminated side of a stem elongate more than cells on the shaded side. T/F Phototropism is triggered by blue light. T/F Phototropins play a significant role in phototropism. T/F The bending of the plant is due to cell elongation in response to auxin.

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Step 1: Evaluate the first statement: 'Cells on the illuminated side of a stem elongate more than cells on the shaded side.' This statement is False. In phototropism, cells on the shaded side of the stem elongate more than those on the illuminated side, causing the plant to bend towards the light source.

Step 2: Evaluate the second statement: 'Phototropism is triggered by blue light.' This statement is True. Blue light is known to trigger phototropism in plants.

Step 3: Evaluate the third statement: 'Phototropins play a significant role in phototropism.' This statement is True. Phototropins are proteins that respond to blue light and initiate the phototropic response.

Step 4: Evaluate the fourth statement: 'The bending of the plant is due to cell elongation in response to auxin.' This statement is True. Auxin is a plant hormone that promotes cell elongation. In phototropism, auxin is distributed more on the shaded side of the stem, causing those cells to elongate more and the plant to bend towards the light.

Step 5: Summarize the evaluations: The first statement is False, while the second, third, and fourth statements are True.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Phototropism

Phototropism is the growth response of a plant toward or away from light. This phenomenon is primarily observed in stems and leaves, where the plant bends towards the light source, maximizing light absorption for photosynthesis. The differential growth rates on the illuminated and shaded sides of the plant are crucial for this bending effect.

Auxin

Auxin is a plant hormone that regulates various aspects of growth and development, including phototropism. When light is detected, auxin is redistributed to the shaded side of the plant, promoting cell elongation there. This unequal distribution of auxin causes the plant to bend towards the light, as the cells on the illuminated side grow less.

Phototropins

Phototropins are a class of photoreceptors in plants that are sensitive to blue light. They play a critical role in initiating the phototropic response by detecting light direction and triggering the signaling pathways that lead to auxin redistribution. This mechanism is essential for the plant's ability to adapt its growth in response to light conditions.

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