STOMATA-structure and function

STOMATA:


Stomata are the structures which is present on the epidermis of leaf mainly but in some plants it is also present in stems.

*In Monocots stomata is dum-bell in shape

*Whereas in Dicots it is bean shaped.


Stomata consist of two types of cells. They are:


1. Guard cells

2. Subsidiary cells.


1. Guard cells:


In Dicots the guard cells are bean shaped whereas in monocots guard cells are dum-bell shape.

There are two guard cells in each stomata.

As the stomata is bean shaped, the curved walls of stomata are thin and it has elasticity which means it has microfibrils through which water gets absorbed by the cell.

A stomatal pore is present between the two guard cells.

Inside the guard cells cytoplasm, organelles and chloroplast is present. Chloroplast helps in photosynthesis.

When the cell absorbs the sunlight, chloroplast gets activated and forms sugars inside the cell. as a result the concentration inside the cells gets increased and osmosis process takes place. that is
outside the guard cells it has subsidiary cells which contains water. The water from subsidiary cells goes inside the guard cells, cells become turgid and gets expanded in its structure and the stomatal pore or stomatal aperture gets open.

Similarly, when there is no sunlight the water goes out of the cell and cells becomes flaccid.

stomata generally opens at day time and closes at night time.

2.Subsidiary cells:


Subsidiary cells are present around the guard cells. There are number of subsidiary cells surrounding the guard cells.

Subsidiary cells contains water which transports to the guard cells, when it contains higher concentration inside the guard cell. These are thin walled cells.

                                Related image

Functions:

* Main function of stomata is the exchange of gases.  Both carbon di oxide and oxygen gets exchange through this.

*It helps in transpiration.

*Participates in photosynthesis due to the presence of chloroplast inside the guard cells.

*Forms sugars and then convert into starch.

*Starch gets distributed to the storage organs and also to the different parts of the plant.



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