4
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: CO2 fixation occurs only during C3 cycle.
Assertion: Dark reaction occurs only at night in the stroma of chloroplast.
Reason: CO2 fixation occurs only during C3 cycle.
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Solution
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
CO2 fixation is common in both C3 and C4 plants. CO2 gets fixed by Calvin cycle in both these type of cycles.
However, in C4 plants, the initial CO2 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.
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
CO2 fixation is common in both C3 and C4 plants. CO2 gets fixed by Calvin cycle in both these type of cycles.
However, in C4 plants, the initial CO2 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.
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