UPSC Prelims 2018 · Question 2 of 99

UPSC Prelims 2018 question on Desert Plant Adaptations

Which of the following leaf modifications occur(s) in the desert areas to inhibit water loss?

1. Hard and waxy leaves
2. Tiny leaves
3. Thorns instead of leaves

Select the correct answer using the code given below:

  1. 2 and 3 only
  2. 2 only
  3. 3 only
  4. 1, 2 and 3
Show answer

Answer: D. 1, 2 and 3

Analysis

All three modifications reduce water loss in desert plants, so the answer is (d) 1, 2 and 3.

Statement by statement

Statement 1 is CORRECT. A thick, waxy cuticle on hard leaves is a standard xerophytic device for preventing transpiration loss.

Statement 2 is CORRECT. Xerophytes typically have leaves that are few, tiny, or needle like, cutting the surface area available for transpiration.

Statement 3 is CORRECT. Leaves reduced to spines only is explicitly listed among the water conservation modifications of xerophytes, the cactus being the familiar example.

Source

NCERT Class 6, Chapter 9, pages 83 and 84.

How to crack it

The chain runs from one principle, not three facts. Transpiration scales with exposed leaf surface and how freely water escapes it, so anything that shrinks the surface or seals it must qualify. Test each item against that principle instead of recalling a list. Note too that when every listed item illustrates the same phenomenon, the all-inclusive option is usually right, and aspirants lose this by assuming UPSC would not make (d) correct so plainly.

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