Plants normally flowering in winter remain vegetative in summer even if they are kept at winter temperature because

Options

A. Transpiration rate becomes very high during summer
B. Laws of limiting factors are applicable in summer
C. Pollination fails to take place in summer
D. They do not get the required day length during summer

Answer

To solve the question regarding why plants that normally flower in winter remain vegetative in summer even when kept at winter temperatures, we can break down the reasoning step by step:

### Step-by-Step Solution:

1. **Understanding Plant Growth Conditions**:
- Plants have specific environmental conditions that trigger their growth and flowering. These conditions include temperature, light duration (photoperiod), and water availability.

2. **Identify the Plant Type**:
- The question refers to plants that typically flower in winter. These are usually classified as "short-day" plants, which require longer nights (or shorter days) to initiate flowering.

3. **Effects of Temperature**:
- While temperature can influence plant growth, simply keeping these plants at winter temperatures during summer does not guarantee flowering. Other factors must also be considered.

4. **Importance of Day Length**:
- For the plants in question, the critical factor is the photoperiod. These plants require a specific duration of light (usually less than 12 hours) to trigger flowering. In summer, the days are longer, which means they do not receive the necessary light conditions for flowering.

5. **Conclusion**:
- Therefore, even if these plants are kept at winter temperatures, they will remain vegetative in summer because they do not receive the required day length to induce flowering.

6. **Final Answer**:
- The correct answer to the question is that these plants do not get the required day length during summer, which is option D.