In succulent plants, the stomata open in the night and close in the day . which among the following would be the best hypothesis to explain the Mechanism of stomatal in the night only?

Options

A. `CO_2` accumulates, reduces pH, stimulate enzymes resulting in accumulation of sugars.
B. Increases in `CO_2` concentration , conversion of organic acids into starch resulting in the increased conversation into sugars resulting in `K^+` transport
C. Low `CO_2` concentration accumulates organic acids resulting in the increased conversion into sugars resulting in `K^+` transport.
D. `CO_2` used up , increase pH results in accumulation of sugars.

Answer

To solve the question about the mechanism of stomatal behavior in succulent plants, we need to understand the physiological processes that occur during the night when these plants open their stomata.

### Step-by-Step Solution:

1. **Understanding Succulent Plants**:
- Succulent plants, such as cacti, have adapted to store water in their leaves and stems. This adaptation allows them to survive in arid environments.

2. **Stomatal Behavior**:
- In succulent plants, stomata open at night and close during the day. This is contrary to most plants, which typically open their stomata during the day for photosynthesis.

3. **Nighttime Processes**:
- During the night, there is incomplete oxidation of carbohydrates. This means that the carbohydrates produced during the day are not fully broken down.

4. **Accumulation of Organic Acids**:
- As a result of this incomplete oxidation, organic acids accumulate in the plant cells. The primary organic acid that accumulates is malic acid.

5. **Role of CO2**:
- The accumulation of organic acids leads to a situation where carbon dioxide (CO2) does not get released. Instead, CO2 accumulates in the guard cells of the stomata.

6. **Effect on Guard Cells**:
- The accumulation of CO2 in the guard cells leads to a decrease in pH (acidification). This acidification stimulates enzymes that result in the accumulation of sugars.

7. **Turgor Pressure**:
- The increase in sugars and organic acids in the guard cells increases their turgor pressure, causing the stomata to open.

8. **Conclusion**:
- Therefore, the best hypothesis to explain the mechanism of stomatal opening at night in succulent plants is that CO2 accumulates, reduces pH, stimulates enzymes, and results in the accumulation of sugars.

### Final Answer:
The best hypothesis is: **CO2 accumulates, reduces pH, stimulates enzymes resulting in the accumulation of sugars.**

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