Question

To avoid photorespiration in $C_4$ plants, RuBisCo activity is restricted in the ___ of chloroplast.

Answer 1

To avoid sluggish behaviour of RuBisCo leading to photorespiration (oxygenation) in $C_4$ plants, $C{O}_2$ molecules are first fixed in mesophyll chloroplast by PEPcase ($C_4$ cycle) to form oxaloacetic acid. The oxaloacetic acid is then moved to the bundle sheath cells and decarboxylated to release CO${}_2$. The carbon dioxide concentration thus increases in the bundle sheath cells and is fixed by RuBisCo ($C_3$ cycle).