Question

What is the optimum temperature required for $C_3$ plants?

• A. $30-{40}^{\circ }C$
• B. $20-{25}^{\circ }C$
• C. Above ${40}^{\circ }C$
• D. Above ${25}^{\circ }C$

Answer 1

The correct option is B $20-{25}^{\circ }C$

$C_3$ plants are those which exhibit the $C_3$ pathway and use the Calvin cycle in the dark reaction of photosynthesis. The optimum temperature required for $C_3$ plants is $20-{25}^{\circ }C$. In $C_4$ plants the optimum temperature range is $30-{40}^{\circ }C$. $C_4$ plants respond to higher temperatures with enhanced photosynthesis due to the $C{O}_2$ concentrating system that inhibits RuBisCO oxygenase activity while $C_3$ plants have much lower temperature optimum. At low temperatures enzymes become inactive and reduce photosynthesis rate and very high temperatures cause denaturation of enzymes.