Cuticular Transpiration

The process of transpiration includes the water molecules which are removed from the plant tissues through the aerial parts of the plants. Very small amount of water is absorbed by the plants which is utilised in growth and development. The rest of it would be eliminated in the form of respiration. There are several types of respiration which we will discuss further in this article. 

Types of transpiration 

There are basically three types of transpiration in plants – 

1. Cuticular transpiration – transpiration when it takes place through the cuticle of the plants is known as cuticular transpiration. It’s a waxy coating on the surface of the leaves of plants where about 5- 10% of water is lost from the leaves through this cuticular transpiration. When the stomata is closed during the dry conditions, more water is transpired through cuticles. 
2. Lenticular transpiration – in the bark and branches of twigs in plants, lenticels are small or minute openings where the evaporation of water takes place. However, lenticels are not present in most of the plants. Very minimal amount of water is lost through it. 
3. Stomatal transpiration – the evaporation of water takes place through the stomata of the plants. This process of losing water is most common in plants as the water near the surface of the leaves changes into vapour and evaporates when the stomata are open. 

Importance of cuticular transpiration in desert plants 

The integrity of the cuticular transpiration barrier even at elevated temperatures is very important especially for hot desert plants. Currently, depending on the temperature of the leaf cuticular water permeability and its relationship with the chemistry of the cuticles are not known for a single desert plant. In this ecological literature it is often claimed that desert plants have specifically adapted themselves to reduce the transpiration by combining a particularly effective stoma control and the presence of cuticular transpiration barrier with extra low permeability. Intuitively, it seems to be plausible but has never been tested whether the cuticular transpiration barrier of desert plants is indeed more effective than the species growing in more humid habitats.

Diagram of Cuticular Transpiration

So here is a cuticular transpiration diagram to better understand the process. 

Ascent of Sap 

When the water evaporates through leaves, a pull is created through the xylem and the water moves back to the leaves. This process is known as transpiration pull. 

The ascent of sap which is driven by transpiration depends on the following properties of water – 

1. Cohesion – it’s a mutual attraction between molecules of water. 
2. Adhesion – the attraction of water molecules towards polar surfaces. 
3. Surface tension – the molecules of water get more attracted to each other in the liquid phase than the gas phase. 

Drawbacks of cuticle transpiration 

The drawbacks of cuticle transpiration are – 

1. It slows down the rate of transpired water which is not compensated by absorption from the soil. 
2. A lot of energy is reduced during the cuticle transpiration. 
3. Most of the unnecessary water is absorbed by the plants during the process.

Conclusion 

Hence it can be concluded that transpiration of plants is a crucial process where excess water will get accumulated in the plant cells and the cells will eventually burst.  So more than 15% of the earth’s moisture is through this process as it’s known to be a part of the water cycle. There are certain types of transpiration which are lenticular, stomatal and cuticular transpiration among which cuticle transpiration is the most significant one. It’s the evaporation process of water through the cuticle of the plants. Cuticle is nothing but a waxy covering which is prevalent on the surface of the leaves of a plant. Most of the water is lost from the leaves through this process. During the dry conditions when stomata are closed, more water is transpired through the cuticles.