The active spectrum of transpiration is

Options

A. Green and ultraviolet
B. Orange and red
C. Blue and far red
D. Blue and red

Answer

To determine the active spectrum of transpiration, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Transpiration**: Transpiration is the process by which water vapor is lost from the plant to the atmosphere, primarily through small openings called stomata.

2. **Role of Stomata**: Stomata are crucial for transpiration. They open and close in response to environmental factors, particularly light.

3. **Light and Stomata Opening**: Stomata open in response to light. This means that the type of light can influence the rate of transpiration.

4. **Identify the Action Spectrum**: The action spectrum refers to the range of light wavelengths that are most effective in promoting a particular biological process. For transpiration, the action spectrum consists of red and blue light.

5. **Effectiveness of Blue Light**: Among the light wavelengths, blue light is particularly effective in stimulating the opening of stomata. This makes it a key player in the transpiration process.

6. **Conclusion**: Since the action spectrum of transpiration includes both red and blue light, and blue light is the most effective in opening stomata, we conclude that the active spectrum of transpiration is red and blue light.

### Final Answer:
The active spectrum of transpiration is **blue and red light**.