Question

In the leaves of C4 plants, malic acid formation during CO₂ fixation occurs in the cells of?

• A. Phloem
• B. Mesophyll
• C. Epidermis
• D. Bundle Sheath

Answer 1

The correct option is B

Mesophyll

The correct option is B.

Explanation for the correct answer:

1. Chlorophyll pigment is present in mesophyll cells in the C4 plants where carbon dioxide fixation takes place.
2. Thus, the production of malic acid happens in mesophyll cells.

Explanation for the incorrect answer:

Option A:

1. Phloem is a vascular tissue whose function is to transport the organic nutrients from leaves to other parts of the plants.
2. It does not take part in CO₂ fixation during photosynthesis.

Option C:

1. The epidermis is the outermost layer of the cells of the stem, roots, fruits, etc.
2. It has a waxy cuticle which provides protection to the plants from mechanical injury and water loss.

Option D:

1. Bundle sheath has chloroplast which is the site for the Calvin cycle (dark reaction) of photosynthesis.
2. It is surrounded by mesophyll cells. This arrangement is known as Kranz anatomy.

Final answer: Mesophyll is the site of production of Malic acid during fixation of CO_2.