Lesson 2 of 10 · 7 min
Epidermis and stomata
NCERT §6.1.1, Figure 6.1
Meera peels a thin film off the underside of a leaf with forceps and mounts it. Instead of a plain sheet, she sees tiny paired sausages scattered among jigsaw-shaped cells.
The lesson in notes
In short
In the primary body of a plant, the epidermis is the layer on the very outside. Its cells are elongated and packed tightly into one unbroken layer, which is usually a single cell thick.
Epidermal cells are parenchyma: a large vacuole with only a thin film of cytoplasm pressed against the wall.
A waxy, thick cuticle often covers the outer surface and cuts down water loss. Roots have no cuticle.
Stomata are found in the epidermis of leaves and control transpiration and the exchange of gases.
Each stoma has two guard cells around a pore. Guard cells are bean-shaped in most plants but dumb-bell shaped in grasses.
The wall of a guard cell facing the pore (inner wall) is heavily thickened; the wall away from the pore (outer wall) is thin. Guard cells contain chloroplasts and control opening and closing.
Epidermal cells next to the guard cells may change shape and size; these are subsidiary cells.
Stomatal apparatus = stomatal pore + guard cells + the subsidiary cells around them.