Question

Under what conditions are $C4$ plants superior to $C3$ ?

Answer 1

$C4$ plants are superior to $C3$ plants on the following basis:

High temperature :
$C4$ plants can survive at high temperatures and still show an increased rate of photosynthesis while $C3$ plants show a decreased rate of photosynthesis at high temperatures.

Low $C{O}_2$ concentration :

At low $C{O}_2$ concentration, $C4$ plants can perform photosynthesis at a good rate while $C3$ plants will show photorespiration at low $C{O}_2$ concentration.