Aspirant Academy
ENHI

RAS question

ASSERTION (A): Tropical rainforest trees develop buttress roots — large triangular root flanges extending outward from the base of the trunk. REASON (R): The nutrient-rich, deep soils of tropical rainforests cannot support the weight of tall trees through conventional root systems alone, necessitating additional structural support. Select the correct answer using the codes given below:

Correct answer: (C) A is true, but R is false.

Tropical rainforest trees do develop buttress roots for stability, but the given reason is false because rainforest soils are not nutrient-rich deep supports; they are generally nutrient-poor and often shallow or saturated near the surface.

  1. (A)

    Both A and R are true, and R is the correct explanation of A

  2. (B)

    Both A and R are true, but R is NOT the correct explanation of A

  3. (C)

    A is true, but R is false

  4. (D)

    A is false, but R is true

Explanation

Assertion A is true: buttress roots are large, plank-like flanges spreading outward from the trunk base, and they help tall tropical trees resist toppling. Britannica describes buttress roots as extensions of lateral surface roots that stabilise trees, especially in shallow saturated soils. Reason R is false because it reverses the soil condition. Tropical rainforest soils are not nutrient-rich deep stores; nutrients are rapidly cycled through biomass and litter, while heavy rainfall and leaching leave the soil poor in available nutrients. Britannica's rainforest account also notes that many rainforest trees have shallow root systems, with food-gathering roots close to the surface. The correct relationship is therefore: buttress roots support tall trees in shallow, wet rainforest soils, not in deep, nutrient-rich soils.

Why the other options are wrong

  • (A) A treats R as true and explanatory, but R wrongly describes tropical rainforest soils as nutrient-rich and deep rather than nutrient-poor with shallow or saturated rooting conditions.
  • (B) B says both statements are true, whereas R is factually false because the soil premise behind it is wrong.
  • (D) D rejects the assertion even though buttress roots are a recognised structural adaptation of many tropical rainforest trees, and it accepts a false reason.

Concept

This tests tropical rainforest adaptations, especially how vegetation responds to soil and moisture conditions. RAS often uses assertion-reason items here because candidates must connect plant form with ecological processes, not just memorise terms.

Source

Related questions