The stomata is a tiny opening or pore that is used for gas exchange. They are mostly present on the     under-surface of plant leaves. In stomata, there is the chlotoplast, a cell wall, a vacuole and a cell nucleus . Air enters the plant through these openings. The poreis formed by a pair known as guard cells. These adjust the size of the opening by opening or closing. To open a guard cells, protons (Hydrogen ions, H+) are pumped into the guard cells. Water enters them, the cells get hard, and they push

open.