Antitranspirant
🔸Antitranspirant is any material applied to transpiring plant surfaces for reducing water loss from the plant.
🔸These are of four types:
🔹Stomatal Closing
🔹Film forming
🔹Reflective
🔹Growth retardant
🔸Stomatal Closing
Most of the transpiration occurs through the stomata on the leaf surface.
Fungicides like phenyl mercuric acetate (PMA) and herbicides like atrazine in low concentrations serve as antitranspirants by inducing stomatal closing.
These might reduce the photosynthesis also simultaneously. PMA was found to decrease transpiration to a greater degree than photosynthesis in a number of plants.
🔸Film forming type
Plastic and waxy materials which form a thin film on the leaf surface retard the escape of water due to formation of physical barrier.
Mobileaf, hexadeconol, silicone are some of the film forming type of antitranspirants. The success of these chemicals is limited since they also reduce photosynthesis.
The desirable characteristics of film forming type of antitranspirants are:They should form a thin layer,They should be more resistant to the passage of water vapour than carbon dioxide and the film should maintain continuity and should not break
🔸Reflectant type
These are white materials which form a coating on the leaves and increase the leaf reflectance (albedo). By reflecting the radiation, they reduce leaf temperatures and vapour pressure gradient from leaf to atmosphere and thus reduce transpiration.
Application of 5 per cent kaolin spray reduces transpiration losses.A diatomaceous earth product (celite) also increases reflection of solar radiation from crop canopy
🔸Growth retardant
These chemicals reduce shoot growth and increase root growth and thus enable the plants to resist drought. They may also, induce stomatal closure.
Cycocel is one such chemical useful for improving water status of the plant
🔸Antitranspirants generally reduce photosynthesis. Therefore, their use is limited to save the crop from death under severe moisture stress. If crop survives, it can utilise the rainfall that is received subsequently. Antitranspirants are also useful for reducing the transplantation shock of nursery plants. They have some practical use in nurseries and horticultural crops.
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