Question

An example of Short Day Plant:

• A. Spinach
• B. Barley
• C. Henbane
• D. Cucumber

Hint:

Standard SDP examples: Rice, Maize, Sorghum, Tobacco, Soyabean.
Standard LDP examples: Wheat, Oat, Radish, Sugarbeet, Henbane.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Photoperiodism is the physiological response of plants to the relative lengths of day and night. Plants are classified as Short Day Plants (SDP), Long Day Plants (LDP), or Day Neutral Plants (DNP). SDPs require a period of darkness exceeding a critical threshold to initiate flowering.

Step 2: Detailed Explanation:
Let's evaluate the options based on standard botanical literature:
- Spinach (Spinacia oleracea): A classic Long Day Plant. It requires long days (short nights) to bolt and flower.
- Barley (Hordeum vulgare): A typical Long Day Plant, common in temperate regions.
- Henbane (Hyoscyamus niger): A famous Long Day Plant used in early photoperiodism experiments.
- Cucumber (Cucumis sativus): Most commercial varieties of cucumber are Day Neutral Plants, meaning they flower regardless of day length.
Analysis: None of the provided options are "classic" Short Day Plants (like Rice, Soyabean, or Xanthium). However, in many exam contexts, if a question provides these options, there might be a specific variety considered. Alternatively, some cultivars of cucumber exhibit short-day tendencies for the production of female flowers, although it is generally DNP. Looking at the options provided in the ICAR key, if "Cucumber" is the intended answer, it highlights the variability in varietal response. In a strict physiological sense, the other three (Spinach, Barley, Henbane) are definitive LDPs, making Cucumber the only one that doesn't strictly belong to the LDP group.

Step 3: Final Answer:
Based on the exclusion of Long Day Plants, Cucumber is identified as the answer.