Question

Identify crops based on water requirement
(A). Maize $<$ Sugarcane $<$ Cowpea
(B). Sunflower $<$ Pearl millet $<$ Soybean
(C). Rice $<$ Sorghum $<$ Redgram
(D). Pineapple $<$ Amaranthus $<$ Cotton
Choose the correct answer from the options given below:

• (A) and (C) only.
• (B) and (D) only.
• (C) and (D) only.
• (D) only.

Hint:

CAM plants (like pineapple) are highly water-efficient because they open their stomata at night to capture $\text{CO}_2$, minimizing transpirational water loss during the day.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Different crops have distinct water requirements based on their photosynthetic pathway ($\text{C}_3$, $\text{C}_4$, or CAM), leaf surface area, stomatal conductance, and total growing duration.

Step 2: Detailed Explanation:
Let's analyze the water requirement trends for each option:
- Option (A): Sugarcane has one of the highest seasonal water requirements of any crop (1500–2500 mm) due to its long growing season.
Cowpea has a very low water requirement (350–500 mm).
Therefore, the sequence Maize $<$ Sugarcane $<$ Cowpea is incorrect.
- Option (B): Pearl millet is an extremely drought-hardy $\text{C}_4$ crop with a low water requirement (250–350 mm), which is lower than both sunflower and soybean.
Therefore, this sequence is incorrect.
- Option (C): Rice is a highly water-intensive crop with a seasonal water requirement of 1200–1500 mm, which is much higher than both sorghum and redgram.
Therefore, this sequence is incorrect.
- Option (D): This sequence is correct:
1. Pineapple: A CAM plant with thick, waxy leaves. It has an extremely low water requirement (about 300–400 mm).
2. Amaranthus: A fast-growing $\text{C}_4$ crop with a moderate water requirement (about 400–500 mm).
3. Cotton: A long-duration $\text{C}_3$ crop with a high seasonal water requirement (700–1300 mm).
This matches the sequence: Pineapple $<$ Amaranthus $<$ Cotton.

Step 3: Final Answer:
The only correct water requirement sequence is given in statement (D).