Who first demonstrated the $C_4$ pathway?

By looking at which internal structure of a plant can you tell whether a plant is $C_{3}$ or $C_{4}$? Explain.

Plants like sugarcane show high productivity and high efficiency of $CO_2$ fixation,because of

In $C_4$ plants,the Calvin cycle occurs in

Dimorphism of chloroplast is found in

As compared to a $C_{3}$-plant,how many additional molecules of $ATP$ are needed for the net production of one molecule of hexose sugar by $C_{4}$-plants?