Stomata are small pores on plant leaves that allow for gas exchange. They open and close through changes in turgor pressure of guard cells surrounding each stoma. During the day, guard cells become turgid through ion transport, opening the stoma to intake CO2 and release O2. At night, guard cells become flaccid through ion efflux, closing the stoma. Various environmental factors like light, temperature, and CO2 levels influence this process of stomatal movement and gas exchange.

3. OUTELINES
 1. Definition of stomata .
 2. Structure of stomata .
 3.Processes of opening and
closing of stomata.
 4. factors affecting of
movement.

4. WHAT IS STOMATA ?
 Stomata are pore in plants skin through
which water and gases are exchanged
between the plant and the atmosphere.
 Stomata are very small can not see without
microscope.

6. STRUCTURE OF STOMATA
 The structure of stomata consists of
minute pores called stoma ,
surrounded by guard cells.
 Guard cells are specialisied
parenchyma cells , savings the
plants from water loss.
 Guard cell are kidney shaped in
dicot plants and dumb-bell shaped
in monocots.
 Each guard cell is a modified
epidermal cell showing a prominent
nucleus, cytoplasm and plastids.
Dicot stomata
Monocot stomata

8.  The wall of the guard cell is
differentially thickened. The inner
wall of each guard cell facing the
stomata is concave and is thick rigid.
 The guard cells are surrounded by a
variable number of epidermal cells
called subsidiary cells.

10. OPENING AND CLOSING OF STOMATA
 Opening and closing of stomata takes place
due to changes in turgor pressure of guard
cells.
 During the day water from subsidiary cell
enters the guard cell making the guard cells
fully turgid and the stomata open.
 During night time water from guard cells
enters the subsidiary cells and as a result the
guard cells become flaccid due to decrease in
turgor pressure and the stomata close.

11. GASEOUS EXCHANGE IN STOMATA
 When the stomata are opened the plant can
take the carbon dioxide (Co2) from the air for
photosynthesis and release oxygen(a by
product of photosynthesis) back in to the
environment.

13. MECHANISM OF STOMATA
 Many theories have been
proposed regarding opening
and closing of stomata.
 Some important theories are –
 1.Starch –Sugar hypothesis.
 2.Active pottasium ion influx
theory.

14. STARCH-SUGAR HYPOTHESIS
 Lloyed(1908) suggested that in the guard cells
starch is converted into sugar during day time.
 As a result the osmotic concentration
increases causing endosmosis and opening of
stomata.
 During night sugar is converted back into
starch leading to exosmosis and closure of
stomata.

15. ACTIVE K+ TRANSPORT ION CONCEPT.
 The concept of k+ ion
transport was given by
fujino. It was supported and
elaborated by Levitt in 1975.
 It appears to be an active
mechanism which needs
ATP.
 Plant hormones play
important role in stomatal
movement.

16. In this theory during day time in the stomata-
 Decreases in starch contents of guard cells.
 Increases concentration of malic acid in guard
cell.
 Influx of K+ ions in guard cells.
 Efflux of H+ ions from guard cells.

17. CONCENTRATION
 Intake of cl+ ions by guard cells.
 Low Co2 concentration in an around guard
cells.
 High pH(more than 7) in guard cells.
 High T.P in guard cells due to endosmosis.

18. CLOSING OF STOMATA IN ABSENCE OF LIGHT.
 In this theory during night-
 Decreased concentration of malic acid in
guard cells.
 Efflux of k+ ions from guard cells.
 Acidic medium of the cell sap in guard cells.
 Loss of Cl- ions from guard cells.

19. CONCENTRATION
 Increase Co2 concentration in and around
the guard cells.
 Presence of plant growth inhibiting hormone
abscissic acid.

21. FACTORS AFFECTING STOMATAL MOVEMENT.
 1. Light
 2.Temperature
 3.Potassium chloride
 4.Organic acid
 5.Carbondioxide conc.
 6.Water
 7. Abscisic acid

22. CONCLUSION
 We know that the stomata is a pore in a
plants skin and usually it is limited on the
lower side of the leaves.
 In monocot leaves the stomata are equally
distributed on both sides and in dicot lower
side of the leaves provided with stomata.
 So it is concluded that stomata is very
important for plants.