Question

Assertion (A): Desert plants take CO2 at night.

Reason (R): They avoid faster evaporation of transpirational water.

• A. Both A and R are false.
• B. Both A and R are true, and R is the correct explanation for A.
• C. Both A and R are correct, but R is not the explanation for A.
• D. A is true, and R is false.

Answer 1

The correct option is B

Both A and R are true, and R is the correct explanation for A.

The correct option is A:

Explanation for the correct option:

Statement:

1. The climate in the desert is extremely hot, and it rarely rains there.
2. Desert plants produce food by photosynthesis, which is a process in which tiny holes (stomata) on the leaves and stems of plants are left open to absorb CO2 from the surrounding atmosphere.
3. However, the plant loses some water each time it opens a hole.
4. The water will quickly evaporate if this occurs repeatedly throughout the day because of the high temperature.
5. Desert plants avoid this by delaying the opening of their carbon dioxide pores until after sunset.

Reason:

1. It has flat, green stalks that serve as both water reservoirs and photosynthetic kitchens.
2. Additionally, the stem has a thick wax layer covering it that aids in water absorption.
3. To absorb water, its roots penetrate the ground deeply.
4. To prevent water loss, the leaves are transformed into spines.

Final answer: Both A and R are true, and R is the correct explanation for A.