Question

Assertion :$C_4$ photosynthetic pathway is more efficient than the $C_3$ pathway Reason: Photorespiration is suppressed in $C_4$ plants

• A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
• B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion
• C. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

$C_4$ photosynthetic pathway is more efficient than $C_3$ pathway as $C_4$ plants can pick up $C{O}_2$ even when it is found in low concentration. PEP enzymes shows high affinity for $C{O}_2$. $C_4$ plants contain two types of chloroplast, bundle sheath chloroplast and mesophyll chloroplast. Bundle sheath cells contain Calvin cycle enzymes. Due to high concentration of $C{O}_2$ in bundle sheath cells RuBP carboxylase works only for calvin and not for photorespiration.
Photorespiration is a wasteful process as it works to undo the act of photosynthesis in $C_4$ plants. No energy rich compound is produced in this process. When temperature increases more and more photosynthetically fixed carbon is lost by photorespiration thus reducing the efficiency of $C_3$ plants.

So, the correct answer is 'Both Assertion and Reason are correct and Reason is the correct explanation for Assertion'.