Question

Which one is not the correct ideotype for dryland farming?

• A. Thick leaves
• B. Shallow root system
• C. Leaves horizontally oriented
• D. High water requirement

Hint:

Ask which single trait would make a crop fail, not succeed, on scarce and unreliable rainfall.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
An ideotype is the ideal combination of plant traits bred or selected for a particular growing condition. Here we need the trait that does not belong in the ideotype meant for dryland, that is rainfed, moisture scarce farming.

Step 2: Key Formula or Approach:
A dryland crop ideotype is built around surviving and yielding on limited, erratic rainfall. Standard traits listed for this ideotype include a deep, well spread root system to draw on stored subsoil moisture, small and thick xeromorphic leaves that cut down transpiring surface, a more erect or vertical leaf orientation to reduce direct heat and radiation load, early maturity to escape terminal drought, and above all a low water requirement together with high water use efficiency.

Step 3: Detailed Explanation:
Thick leaves are consistent with a dryland ideotype, since a thicker, more leathery leaf with a heavier cuticle loses less water to transpiration than a thin, soft leaf.
A more vertical or erect leaf orientation is also consistent with the standard dryland ideotype, since it intercepts less direct solar radiation at midday than a leaf held flat and horizontal, keeping leaf temperature and water loss lower.
A high water requirement is the direct opposite of what a dryland ideotype needs. A crop bred for areas with scarce and unreliable rainfall must be able to complete its life cycle and give an economic yield on a low, not a high, water demand, so this trait cannot belong to a dryland ideotype.
A shallow root system is also generally not favoured for dryland crops, since a deep and well branched root system is usually preferred to tap moisture held lower in the soil profile once the topsoil has dried out, though some short duration dryland crops do rely on a quick, well spread surface root flush to catch light showers; even so, this is a more debated point than the water requirement trait.
Among the four choices, high water requirement is the clearest and most direct contradiction of what a dryland farming ideotype is defined to be.

Step 4: Final Answer:
High water requirement is not a correct ideotype trait for dryland farming.