Specifications of C4 plants: 1) in C4 plants C4 pathway operates under high temperature whereas in C3 plants C3 pathway operates under low temperature.
2) C4 plants contain PEP Carboxylase enzyme. It can fix atmospheric CO2 when its concentration is as low as 2 to 3 ppm (parts per million) whereas in C3 plants (contain RUBISCO enzyme) can fix atmospheric CO2 only when its concentration is more than 50 ppm (parts per million).
3) C4 plants require low humidity while C3 plants require more humidity.
4) C4 plants shows Kranz leaf anatomy which contain two types of chloroplasts viz. Bundle sheath and mesophyll chloroplast whereas C3 plants shows normal leaf anatomy containing only one type of chloroplast.