C3 and c4 plants are adapted to environmental conditions

c4 plants are adapted to a hot environment, unlike c3 plants

Note that c4 plants are "often" cross-pollinated, unlike c3 plants

Very good question...

C4 rice is being attempted for a long time now...

Photorespiration would still be a mandatory physiological process to define net primary productivity, C3 or C4 plant....

As this process waste large amount of energy and not good for best but may be it protects plants from harmful effects of certain molecules.

C3 and c4 plants are adapted to environmental conditions

c4 plants are adapted to a hot environment, unlike c3 plants

Note that c4 plants are "often" cross-pollinated, unlike c3 plants