Pigments of `PS` I occur in

Options

A. Appressed part of granal thylakoids
B. Stromal thylakoids and non-appressed parts of granal thylakoids
C. Both appressed and non-appressed parts of granal thylakoids
D. Stroma

Answer

To answer the question about where the pigments of Photosystem I (PS I) occur, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Photosystems**:
- Photosystem I (PS I) is one of the two photosystems involved in photosynthesis, the other being Photosystem II (PS II). Each photosystem contains pigments that absorb light energy.

2. **Location of PS I**:
- PS I is located on the thylakoid membrane of chloroplasts. Specifically, it is found on the outer surface of the thylakoid membranes.

3. **Thylakoid Structure**:
- Thylakoids can be categorized into two parts: the appressed (or granal) thylakoids and the non-appressed (or stromal) thylakoids. Granal thylakoids are stacked, while stromal thylakoids connect these stacks.

4. **Pigments in PS I**:
- The pigments associated with PS I include chlorophyll a and other accessory pigments. These pigments are primarily located on the outer surface of the thylakoids and in the non-appressed parts of the granal thylakoids.

5. **Evaluating the Options**:
- Option 1: Apparous part of granal thylakoids - Incorrect, as PS I is not located here.
- Option 2: Stromal thylakoids and non-apparous part of granal thylakoids - Correct, as PS I is found in these areas.
- Option 3: Both apparous and non-apparous parts of granal thylakoids - Incorrect, as PS I is not found in the apparous part.
- Option 4: Stroma - Incorrect, as PS I is not located in the stroma itself.

6. **Conclusion**:
- The correct answer is Option 2: Stromal thylakoids and non-apparous part of granal thylakoids.