Question

The following question consist of two statements, printed as assertion and reason. While answering the question, you are required to choose any one of the following five responses.

Assertion: Photosynthetically $C_4$ plants are less efficient than $C_3$ plants.

Reason: The operation of $C_4$ pathway requires the involvement of only bundle sheath cells.

Answer 1

Assertion reason relation

Photosynthetically $C_4$ plants are more efficient than $C_3$ plants because of absence of photorespiration in $C_4$ plants. $C_3$ plants perform photorespiration under low carbon dioxide condition due to oxygenase activity of RuBisCO.

Hence, the given assertion- “Photosynthetically $C_4$ plants are less efficient than $C_3$ plants.” is false.

Assertion reason relation

Two types of cells are involved in $C_4$ pathway- Mesophyll cells and bundle sheath cells. Carboxylation reaction occur in mesophyll cells where oxaloacetic acid is produced (first stable carbon dioxide fixation compound). Oxaloacetic acid is transported to bundle sheath cells where it is utilised in Calvin cycle to produce glucose.

Hence, the given assertion- “The operation of $C_4$ pathway requires the involvement of only bundle sheath cells.” is false.

Final answer

(D) If both assertion and reason are false.