Question

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R
Assertion A: Leaves exposed to the Sun, are thinner, have larger area of lami have more chlorophyll and less stomata.
Reason R: Plants become structurally and physiologically adapted to the amount of solar radiations received.

• A. Both A and R are correct and R is the correct explation of A
• B. Both A and R are correct but R is NOT the correct explation of A
• C. A is correct but R is not correct
• D. A is not correct but R is correct

Hint:

Sun Leaves = THICKER, smaller lami area, dense stomata, thick cuticle (prevents water loss).
Shade Leaves = THINNER, broader lami area, higher chlorophyll content (captures maximum light).

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
The question tests knowledge regarding atomical and physiological leaf adaptations (sun leaves versus shade leaves) under varying solar irradiance levels.

Step 2: Key Formula or Approach:
Plants adapt leaf structure based on solar exposure:
• Sun Leaves: Adapted to high light intensity $\to$ Thicker lami, multi-layered palisade mesophyll, smaller surface area, higher stomatal density, lower total chlorophyll per unit weight.

• Shade Leaves: Adapted to light capture in dim conditions $\to$ Thinner lami, larger surface area (lami), higher total chlorophyll content to maximize light absorption.

Step 3: Detailed Explation:

• Alysis of Assertion A: Assertion A claims that sun leaves are *thinner*, have *larger area*, *more chlorophyll*, and *fewer stomata*. This description actually corresponds to shade leaves. Sun leaves are thicker (due to well-developed palisade tissue), have smaller leaf area to restrict transpiration, higher stomatal density, and less total chlorophyll per weight. Thus, Assertion A is incorrect.

• Alysis of Reason R: Plants demonstrate phenotypic plasticity, adapting both structurally (cuticle thickness, mesophyll layers) and physiologically (photosynthetic capacity, light saturation points) to ambient light levels. Thus, Reason R is correct.

Step 4: Fil Answer:
Assertion A is not correct, but Reason R is correct.