DENDROLOGY

Detailed explanation-1: -Guard cells are cells surrounding each stoma. They help regulate the opening and closing of the stoma. When the guard cells are turgid or swollen, the stomatal opening is large and when the guard cells have lost water or flaccid, the stomatal opening closes.

Detailed explanation-2: -Because of their small size, guard cells are rapidly influenced by turgor changes. Because of their kidney-shaped outline, they remain joined at their ends. This concave-convex curvature of the two guard cells can be varied easily and this further facilitates the stomatal pore to open and close easily.