If an etiolated stem could be first saturated with auxin by spraying and then exposed to a streak of light from one side it will

Options

A. Bend towards the light
B. Bend away from light
C. Grow straight upwards
D. Be prevented from growing

Answer

To solve the question regarding the behavior of an etiolated stem that has been saturated with auxin and then exposed to a streak of light, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Etiolated Stems**:
- Etiolated stems are those that have grown in the absence of light, resulting in elongated, pale stems with small leaves. They are typically seeking light.

**Hint**: Remember that etiolated stems are adapted to grow towards light due to their lack of exposure to it.

2. **Role of Auxin**:
- Auxin is a plant hormone that promotes cell elongation. It is produced at the shoot apex and is crucial for phototropism (growth towards light).

**Hint**: Auxin is essential for directional growth in plants, particularly in response to light.

3. **Saturation with Auxin**:
- When the etiolated stem is saturated with auxin by spraying, it ensures that auxin is uniformly distributed throughout the stem.

**Hint**: Think about how the uniform presence of auxin affects the stem's growth response to light.

4. **Exposure to Light**:
- When the stem is exposed to a streak of light from one side, auxin will redistribute. Auxin tends to move away from the light source, accumulating on the shaded side of the stem.

**Hint**: Visualize how the distribution of auxin changes when one side of the stem receives light.

5. **Cell Elongation**:
- The side of the stem that accumulates auxin (the shaded side) will experience increased cell elongation compared to the side exposed to light.

**Hint**: Consider how differential growth on either side of the stem leads to bending.

6. **Resulting Movement**:
- Due to the differential growth (elongation) caused by auxin, the stem will bend towards the light source.

**Hint**: Remember that the stem bends towards the light because the opposite side (shaded side) is growing faster due to auxin.

### Final Answer:
The etiolated stem will **bend towards the light**.