ANTITRANSPIRANTS AND Different Types of Stomata

 The antitranspirants are any materials applied to the plants for the purpose of retarding transpiration.

In the extreme cases of transpiration, about 98% of water absorbed by the plants is lost and only an insignificant

amount is being utilized by the plant for its own purpose. If by any chance, this enormous loss of water

can be reduced, it will be an asset to nature and also the agriculturists to reduce the transpiration loss

and increase the crop productivity in the rainfed and semi-arid regions. The antitranspiratnts are of three

types.

They are discussed below :

a. Stomata closing type : (eg. Phenyl Mercuric Acetate, ABA, Atrazine, CO2 at high conc., Decenyl succinic

acid, Xanthoxin)

These chemicals will induce stomatal closure and thus transpiration will be reduced. The

the problem with using these chemicals is the photosynthesis will also be affected because of reduced entry

of CO2.

b. Thin film forming type : (eg. Cetyl alcohol, silicone oils, low viscosity waxes, rice gruel)

These substances will form a thin film on the leaf surface. They will inhibit the loss of water vapor

from the leaf. But, they will allow CO2 to pass into the leaf.

c: Reflective Type : (eg. Kaolin, lime water spray)

The principle of using this type of chemicals is to increase the light reflected by the leaves and thus

reducing the leaf temperature. Though the transpiration is reduced, CO2 assimilation will not be affected.

Different Types of Stomata

A. Types of Stomata based on Distribution

There are about five types of stomatal distribution recognized in plants :

1. Apply or mulberry type

Stomata are found distributed only on the lower surface of the leaves. eg., apple, peach.

mulberry, walnut, etc. Such leaves are called a hypostomatic type.

2. Water lily type

Stomata are distributed only on the upper epidermis of the leaves. eg., water lily, Nymphaea, and

many aquatic plants. These plants are epistomatic types.

3. potato type

In this type, the stomata are found more on the lower surface (multistomatic) and less on the upper

leaf surface (paucisymptomatic type). eg., Potato, cabbage, bean, tomato, pea, etc. Such leaves are called amphistomatic and anisostomatic types.

4. Out type

Stomata are equally distributed on both the lower and upper surfaces of the leaves. These leaves are

referred to as the isostatic type.

5. Potamogeton type

In this case, stomata are altogether absent or if present, they are vestigial. eg., Potamogeton and

other submerged aquatics.

B. Types of Stomata based on Movement

Loftfield (1856) classified three main groups of stomata in accordance with their daily movement:

1. Alfalfa Type

The stomata remain open throughout the day and closed all night, eg., peas, bean, mustard, etc.

2. Potato Type

The stomata open only for a few hours in a day, eg., Allium, cabbage, etc.

3. Barley Type

The stomata open only for a few hours in a day, eg., Barley and other cereals.

C. Types of Stomata based on Behavior

Considering the behavior of the stomatal movements, five categories have been recognized :

1. Photo-active movements

Light directly or indirectly controls stomatal movements. Such stomata remain open during the day

time and closed in nights (dark).

2. Skoto-active movements

Stomata remain closed during the daytime and open during the night. Such cases are found in succulent

plants and other CAM Plants.

3. Hydro-active movements

In some cases, stomata open due to excessive loss of water from the epidermal cells and close due to

turgid conditions of epidermal cells. This is usually found during mid-day.

4. Autonomous movements

In certain cases, stomata open and close at a rate of 10-15 minutes showing diurnal or rhythmic

pulsation.

5. Passive and Active movements

Opening of stomata is considered an active process and closing is the passive process and this is

caused by the turgor changes in the guard cells.