Download Stomate cells

Cell types
Stomate
A stomate is composed of a group
of epidermal cells that includes
the guard cells and subsidiary
cells.
Stomata are designed to regulate
gas exchange and transpirational
water loss.
Stomata are most frequently
found on the bottom (abaxial)
side of leaves, but may occur on
the top (adaxial) of leaves, or on
stems and even fruits and seeds.
Back to main
anatomy menu
Next
Back to cell
types menu
Main menu
Cell types
Stomate
A stomatal complex consists of:
Subsidiary
cells
Guard cells
and
Subsidiary cells.
Guard
cell
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Guard cells are a pair of kidney shaped cells that form the opening
of the stomate.
When the guard cells are turgid
(full of water), they are open and
allow gas to enter the stomate.
However, this also exposes the
leaf to potential water loss.
*
*
When the guard cells are flaccid
(less water), they are closed to
prevent air exchange and water
loss.
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Subsidiary cells are cells
bordering the guard cells of
the stomate.
They do not directly
participate in the opening and
closing of the stomate, but can
aid in their functioning through
cellular osmotic activity.
*
*
*
*
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Subsidiary cells vary in their arrangement
and pattern depending on the plant species.
Recognizable patterns include:
Paracytic
Diacytic
Anisocytic
Tetracytic
Anomocytic
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Paracytic – two subsidiary cells on
the lateral sides of each guard cell.
Tetracytic – four
subsidiary cells surround
the guard cells.
Anisocytic – three subsidiary
cells of different sizes
surround the guard cells.
Back to main
anatomy menu
Diacytic – two subsidiary cells on
the poles of the guard cells.
Back
Next
Anomocytic – stomates
lack subsidiary cells.
Back to cell
types menu
Main menu
Cell types
Stomate
Stomates occur mainly on
the abaxial side of leaves,
but can also be seen in
other leaf-like appendages
like sepals and petals.
Stomate on a Begonia petal.
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Stomates can also be produced on the surface of seed coats in some seeds.
Canna lily (Canna)
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Stomata are uncommon on
seed coats, but they occur
in almost 30 different plant
families.
Stomate
It is not certain what role
stomata play in seed
development or germination.
It is suggested that they
function in gas exchange,
possibly to facilitate
photosynthesis in some
seeds and respiration.
Canna lily (Canna) seed coat
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
When the plant is turgid (full of
water) the guard cells are swollen
and the stomate is open. This
allows carbon dioxide to enter the
leaf for photosynthesis, but it also
allows water to leave the opening.
Water leaving the leaf is called
transpiration.
During times of water stress, the
guard cells lose water and shrink.
This closes the stomate. Most
stomata are also closed at night,
since most plants do not need to
fix carbon dioxide in the dark and
the plant does not need to lose
water needlessly.
Back to main
anatomy menu
Back
Next
Closed stomate
Back to cell
types menu
Open stomate
Main menu
Cell types
Stomate
In side view, the stomatal chamber is
evident. The stomatal chamber leads to
air chambers in the mesophyll facilitating
gas exchange across the leaf.
Palisade mesophyll
Spongy mesophyll
Stomatal chamber
Back to main
anatomy menu
Stomates
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Stomates may have recessed guard cells below the level of the epidermis and above
the stomatal chamber. This arrangement is sometimes called a stomatal crypt.
Stomatal chamber
Epidermis
Back to main
anatomy menu
Subsidiary cell
Back
Next
Guard cell
Back to cell
types menu
Main menu
Cell types
Stomate
An electron micrograph
of guard cells reveals
them to be a
metabolically active cell.
Inside leaf
(stomatal chamber)
Mitochondria
Cell wall
Nucleus
There is a large nucleus,
many small vacuoles,
chloroplasts and
numerous mitochondria.
Vacuole
Ledge
Back to main
anatomy menu
Back
Next
Chloroplast
Back to cell
types menu
Main menu
Cell types
Stomate
Stomates in needle-leaf conifers occur in parallel rows.
Fir (Abies) leaf
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Stomates in pine have a
sunken stomate
arrangement.
The guard cells are not
directly on the epidermal
surface and the subsidiary
cells overhang the stomatal
opening.
Subsidiary
cell
A portion of the guard
cells and the subsidiary
cells have lignified walls.
Guard cell
Stomatal chamber
Epidermis
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
An open and closed
stomate in a pine
(Pinus) leaf.
Note the sunken guard
cells and the relatively
large stomatal cavity
associated with each
stomate.
Subsidiary
cell
Open stomate
Back to main
anatomy menu
Back
Next
Closed stomate
Back to cell
types menu
Main menu
Cell types
Stomate
Surface view of stomates by scanning electron microscopy. They appear
to be surrounded by a sea of epidermal surface cuticle wax.
Back to main
anatomy menu
Back
Next
Back to cell
types menu
Main menu
Cell types
Stomate
Some stomates show a wonderful surface pattern over subsidiary
cells made by strands of wax. Wax on the epidermal cells helps to
reduce water evaporation from the surface.
Surface wax in English ivy (Hedera).
Back to main
anatomy menu
Back
Electron micrograph of a
dogwood (Cornus) stomate.
Back to cell
types menu
Main menu