Which of the following plants stands intermediate between $C_3$ and $C_4$ plants?

In leaves of $C_4$ plants,malic acid synthesis during $CO_2$ fixation occurs in:

In succulent plants,the stomata open at night and close during the day. Which among the following would be the best hypothesis to explain the mechanism of stomatal action at night only?

$C_4$ plants are found in:

In Hatch and Slack pathway,the primary $CO_2$ acceptor is

What happens to $C_{4}$ acid in the bundle sheath cells?