The green part of the plant is primarily involved in which of the following processes?

$I.$ Initial $CO_{2}$ acceptor
$II.$ Extent of photorespiration
$III.$ Enzyme catalyzing reaction that fixes $CO_{2}$
$IV.$ Presence of Calvin cycle
$V.$ Leaf anatomy
Which one does not differ in a $C_{3}$ and $C_{4}$ plant?

If $CO_2$ is released during respiration,why does the concentration of $CO_2$ in the atmosphere remain relatively constant?

$CO_2$ is constantly released in respiration,yet its level remains fairly uniform because:

When green algae are illuminated,motile aerobic bacteria usually accumulate near them. This is because,bacteria

In bacterial photosynthesis,which of the following is present?