Question

In C3 plants, photosynthesis occurs in
A. Bundle sheath cells
B. Peroxisomes
C. Mesophyll cells
D. Kranz anatomy

Answer 1

Hint: Photosynthesis, the process by which green plants and certain other organisms transform light energy into chemical energy.

Complete Answer:
- Plants which use the C3 pathway to fix carbon via the Calvin Cycle are called the C3 plants. The stomata are open during the day and closed at night. These plants are predominant in temperate regions.
Example: Soybean. About 85% of the plant species are C3 plants. These plants do not have any adaptations to minimize photorespiration. Unlike C4 plants, C3 plants do not have any separation for $CO_2$ fixation and Calvin cycle.
- Mesophyll cells have many chloroplasts, which contain the specialized light-absorbing green pigments, called chlorophyll. In photosynthesis, the plant utilizes solar energy to oxidize water, thereby releasing oxygen. To reduce carbon dioxide, they form large carbon compounds, mainly sugars.
- Mesophyll cells are the site of photosynthesis in C3 plants.

Hence the correct option is option C, ‘Mesophyll cells’.

- Mesophyll cells are present on leaves, between the upper and lower epidermis. There are 2 types of mesophyll cells: The palisade and the spongy cells.
- The palisade parenchyma is located just under the epidermis of the leaf to absorb more light. They have a lot of chloroplast present on them and are the main site of photosynthesis on leaves.
- The spongy mesophyll cells, located below the palisade cells, have a lot of spaces between them which help the carbon dioxide to move around the leaf. It also helps the plants to bend. The thickness of spongy parenchyma is between 1.5 to 2 times that of palisade cells.
The thin cell wall of the palisade cell allows the gases to easily diffuse through. In spongy cells, photosynthesis occurs at high light intensities.

Note: The mesophyll cells minimize the photorespiration process and supply a stable flow of carbon dioxide to the Calvin cycle even when the stomata are closed.