Question

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

Assertion: Dark reaction occurs only at night in the stroma of chloroplast.

Reason: $C{O}_2$ fixation occurs only during $C_3$ cycle.

Answer 1

Assertion-Reason relation

The term ‘Dark reaction’ doesn’t mean it happens in dark or night. It only means that light is not a direct essential factor for this reaction to occur. So, the step of fixation of carbon dioxide during dark reaction can occur in the presence or absence of light. It can occur both during the day and night time. Hence, assertion statement is incorrect.

Assertion-Reason relation

$C{O}_2$ fixation is common in both $C_3$ and $C_4$ plants. $C{O}_2$ gets fixed by Calvin cycle in both these type of cycles.

However, in $C_4$ plants, the initial $C{O}_2$ fixation occurs in the mesophyll cells. Calvin cycle occurs next in bundle sheath cells.

Hence, the reason statement is incorrect.

Final answer

(D) If both assertion and reason are false.