The structural adaptation of desert plants for water conservation is

Analyze the question: It asks for a structural adaptation that helps desert plants (xerophytes) conserve water. The main challenge in the desert is losing water through transpiration, so the adaptation must reduce water loss.

Explain the concept: Xerophytes reduce transpiration in several ways:

• Reduced leaves, often shrunk into spines (as in cactus), which means less surface area for evaporation
• Thick, waxy cuticle
• Sunken or few stomata, often closed during the day
• Rolled or folded leaves
• Deep or widespread roots, and water-storing stems

Check each option:

• A. Broad leaves with numerous stomata: A large surface area and many stomata would increase water loss. This is wrong.
• B. Spongy mesophyll: This is a normal leaf tissue found in most plants, with air spaces for gas exchange. It is not a special water-saving feature.
• C. Spiny leaves: Leaves reduced to spines have a very small surface area, so they lose very little water through transpiration. This is correct.
• D. Prominent stomata in leaves: Prominent, exposed stomata would lose more water. Desert plants have sunken or reduced stomata instead. This is wrong.

Answer: The correct option is C. spiny leaves.

Tip: For "desert plant / water conservation" questions, think "less surface area, less transpiration." Look for words like spines, reduced leaves, thick cuticle, sunken stomata. Avoid options with broad leaves or numerous stomata.