Anatomy of Flowering Plants
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The outside of the epidermis is often covered with a waxy thick layer
(cuticle).
It prevents the loss of water. Cuticle is absent in roots.
b. Stomata
These are structures present in the epidermis of leaves.
Stomata regulate the transpiration and gaseous exchange. A stoma is
made of two bean-shaped cells (guard cells) which encloses stomatal
pore.
In grasses, the guard cells are dumb-bell shaped. (NEET 2018)
Stomata
Guard cells
Stomata and Guard cells
Epidermal cells
Subsidiary cells
Gaurd cells
Dumb-bell shaped guard cells
The outer walls of guard cells (away from the stomatal pore) are thin
and the inner walls (towards the stomatal pore) are highly thickened.
The guard cells possess chloroplasts and regulate the opening and
closing of stomata.
Sometimes, a few epidermal cells, in the vicinity of the guard cells
become specialized in their shape and size. They are known as subsidiary
cells. (NEET-I 2016)
The stomatal aperture, guard cells and the surrounding subsidiary cells
are together called stomatal apparatus.
c. Epidermal appendages
The cells of epidermis bear a number of hairs.
Root hairs: Unicellular elongations of the epidermal cells. They help to
absorb water and minerals from the soil.
Trichomes: They are the epidermal hairs on the stem. They are usually
multicellular, branched or unbranched and soft or stiff. They may be
secretory. Trichomes help to prevent water loss due to transpiration.