Which of the following factors is the main problem facing xerophytes?

Step 1: Analyze the question The question asks for the main problem facing xerophytes. So we first need to know what a xerophyte is.

Step 2: Explain the concept Xerophytes are plants adapted to live in very dry habitats, such as deserts and semi-arid regions. Examples include cactus, agave, and some acacia species. The Greek root helps: xero means "dry" and phyte means "plant".

Their environment is hot and dry, with very little available water. Because of this, they have developed adaptations such as:

• Thick, waxy cuticles to reduce water loss
• Reduced leaves or spines to cut down transpiration
• Sunken stomata
• Fleshy stems that store water
• Deep or widely spreading roots to reach water

These adaptations are solutions to one core problem: water scarcity.

Step 3: Evaluate the options

• A. Conservation of excess water: Incorrect. Xerophytes do not have excess water. They conserve scarce water, and this is their adaptation, not their problem.
• B. Competition for sunlight: Incorrect. Desert regions are sunny and plants are usually widely spaced, so light is not a limiting factor.
• C. Lack of adequate water: Correct. Dry habitats mean water is the limiting factor for survival.
• D. Formation of poor roots: Incorrect. Xerophytes typically have well-developed roots (deep taproots or extensive shallow networks), so this is not their problem.

Step 4: Answer The main problem facing xerophytes is lack of adequate water, which is option C.

Exam tip: When a question asks about the "problem" of a habitat-based plant group, identify the limiting factor of the habitat first:

• Xerophytes → too little water
• Hydrophytes → too much water, poor aeration
• Halophytes → high salt concentration

Remember that adaptations are the solutions, and the environment supplies the problem.