The wavelength of light absorbed by Pr form of phytochrome is
(a) 620 nm
(b) 640 nm
(c) 680 nm
(d) 720 nm

Options

A. 620 nm
B. 640 nm
C. 680 nm
D. 720 nm

Answer

To solve the question regarding the wavelength of light absorbed by the Pr form of phytochrome, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Phytochrome**: Phytochrome is a photoreceptor pigment in plants that plays a crucial role in regulating various physiological processes, including flowering.

2. **Identify the Forms of Phytochrome**: There are two forms of phytochrome:
- Pr (red light-absorbing form)
- Pfr (far-red light-absorbing form)

3. **Determine the Wavelengths**:
- The Pr form of phytochrome primarily absorbs light in the red region of the spectrum.
- The typical absorption range for the Pr form is approximately 660 to 680 nm.

4. **Analyze the Options**:
- (a) 620 nm
- (b) 640 nm
- (c) 680 nm
- (d) 720 nm

5. **Select the Correct Answer**: Since the Pr form absorbs light in the range of 660 to 680 nm, the closest option that fits this range is:
- **(c) 680 nm**.

### Final Answer:
The wavelength of light absorbed by the Pr form of phytochrome is **(c) 680 nm**.

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