Which does not take place in short day plants ?

Options

A. An interrupted critical dark period
B. Critical period is interrupted by light
C. Dark period is interrupted by red light followed by far-red light
D. Critical period is not interrupted by white or red light.

Answer

### Step-by-Step Solution:

1. **Understanding Short Day Plants**:
- Short day plants are those that flower when the duration of daylight is shorter than a certain critical length. They require a long period of darkness and a short period of light to initiate flowering.

2. **Identifying the Critical Dark Period**:
- The critical dark period for short day plants must be continuous and uninterrupted. If this dark period is interrupted, it can prevent the plant from flowering.

3. **Analyzing the Options**:
- **Option 1**: "An interrupted critical dark period" - This does not occur in short day plants as they require an uninterrupted dark period to flower.
- **Option 2**: "Critical period is interrupted by light" - This is a correct statement for short day plants; they do not flower if their critical dark period is interrupted by light.
- **Option 3**: "Dark period is interrupted by red light followed by far red light" - This can lead to flowering since far red light can reverse the effect of red light, hence this does not apply to short day plants.
- **Option 4**: "Critical period is not interrupted by white or red light" - This is also true for short day plants; they need the dark period to remain uninterrupted.

4. **Conclusion**:
- The option that does not take place in short day plants is "Critical period is interrupted by light". This is because short day plants require an uninterrupted dark period to flower.

### Final Answer:
The correct answer is: **Critical period is interrupted by light**.

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