This document provides information about stomata, including its structure, types, and functions. Stomata are microscopic pores found in plant leaves, stems and other surfaces that allow for gas exchange. They are bordered by a pair of specialized plant cells called guard cells that regulate the opening and closing of the pore. The structure includes the pore, guard cells, and sometimes subsidiary cells surrounding the guard cells. There are different types of stomata classified by the number and arrangement of subsidiary cells. Stomata are important as they allow carbon dioxide to enter and oxygen to exit leaves, facilitating photosynthesis, while also allowing transpiration and maintaining water balance in plants.

1. SHALINI BARA
ASSISTANT PROFESSOR
ST. XAVIER’S COLLEGE, MAHUADANR,
LATEHAR
NILAMBER PITAMBER UNIVERSITY

2. CONTENTS
What is stomata?
Structure of stomata
Types of stomata
Classification of stomata
Functions of stomata

3. What is stomata?
Stomata are minute pores called stoma (singular) which occur in the
epidermis of the plants (especially in lower (sometimes upper) epidermal
layer/ surface of leaves, stem and other areal parts of the plants)
surrounded by a pair of guard cells through which gaseous exchange take
place.

4. structure of stomata
Stomata mainly constitute three parts:
1. Stomata pore
2. Guard cells
3. Subsidiary cells

5. Stomata pore:
 It is the innermost part of stomata.
 It is a small pore- like structure.
 It is present on leaf.
 It helps in gaseous exchange.
 Transpiration (loss of water in the form of water vapour) occurs by this.

6. Guard cells:
 It is a specialized cell surrounding the stomatal pore.
 It is always present in pair.
 Chloroplast always present in guard cell.
 Helps in stomatal openning and closing.

7.  In dicot leaf- kidney- shape guard cell.
 In mocot leaf- dumbell- shape.

8. Arrangement of stomata

9. Subsidiary cell:
 Are the type of epidermal cell surrounding the guard cell.
 Morphologically different from guard cell.
 Also called as accessory cell.

10. Stomatal apparatus:
 Stomatal pore, guard cell and subsidiary cell are
collectively known as stomatal apparatus.

11. Types of stomata
Open and closed type:
 During night time (i.e. in absence of light), stomata remain closed, while during
day time (i.e. in presence of light), stomata will remain opened.
 When stomata is open, transpiration occurs but when it is closed there is no
transpiration.
At night At day

12. On the basis of number of subsidiary cells
surrounding the stomata and their arrangements,
there are four basic types of stomata among the
dicotyledons.
1. Type-A or Anomocytic type or ranunculaceae type
2. Type- B or Anisocytic type or cruciferous type
3. Type-C or Paracytic type or rubiaceous type
4. Type- D or Diacytic type or caryophyllacous type

13. Anomocytic type
 No subsidiary cells are present.
 Stomata remains surrounded by several irregular epidermal cells.
 Aslo called Ranunculaceous type or irregular- celled type.
 Commonly found in several dicots, like Tridax, Citrullus, Ranunculus etc.

14. Anisocytic type
Here stomata surrounded by three subsidiary cells.
Of these, one is distinctly- smaller than the other two.
Also called Cruciferous type or unequal-celled type.
Commonly found in Brassica, Sedum etc.

15. Paracytic type
 One or more subsidiary cells are present.
 Here subsidiary cells arranged in that manner where they are parallel with the
guard cells.
 Also called Rubiaceous type or parallel-celled type.
 Commonly found in members of Rubiaceae, and genera such as Vigna etc.

16. Diacytic type
 Stomata remains surrounded by a pair of subsidiary cells.
 Wall of subsidiary cell remain at right angle to the long axis of the guard cell.
 Also called Caryophyllaceous type or cross-celled type.
 Commonly found in members of Caryophyllaceae (e.g., Diantbus) , Ocimum
etc.

17. Functions of Stomata
The main functions of stomata are:
 Helps in the exchange of gases by opening and closing the pores in the leaves.
 It helps to expel the excess water out from the leaves in the form of water
vapour.
 Based on the weather conditions, it closes or opens its pores to maintain the
moisture balance.
 Allows the uptake of carbon dioxide and to give out oxygen during the process
of photosynthesis.
 Stomata remain open during the day and closed at night. This closure prevents
water from escaping through open pores.

18. THANK YOU.....