Question

Present atmospheric $C{O}_2$ concentration is not limiting factor for $C_4$ plants as $C_4$ plants

• A. Posses PEPcase as primary carboxylase enzyme
• B. Primary carboxylation reaction product is a four carbon acid
• C. No oxygenation of RUBP due to kranz anatomy
• D. Primary carboxylation reaction occurs in mesophyll cells

Answer 1

The correct option is A Posses PEPcase as primary carboxylase enzyme

The $C_4$ plants posses PEPcase as primary carboxylase enzyme which carboxylates $C{O}_2$ that is absorbed from the stomata. In these plants there is a special mechanism, which was developed because they evolved at a time when the climate had low carbon dioxide levels, that converts carbon dioxide to malic acid which is stored and later used so they can keep their stomata closed during the daytime to prevent transpirational loss of water. Hence the concentration of $C{O}_2$ is not a limiting factor for them.

So the correct answer is ' Possess PEPcase as primary carboxylase enzyme'.