Significance of Transpiration: Definition, Types, and Process

Significance of Transpiration: Do you know plants also cool their surface when the temperature is high? They also contribute to the water cycle. Humans aren’t the only living things that sweat to lower their body temperature. When trees and plants “sweat,” they cool themselves and their surrounding air by the process of transpiration. The plants uptake an abundant quantity of water from the soil through their root hairs, and some of the water drawn up through the roots exits the plant through tiny pores present on the surface of leaves. These tiny pores present in the leaves open for the exchange of gases during photosynthesis. During the same time when the pore is open, water is also lost in the form of vapour. So, we can say that transpiration is the inevitable consequence of gas exchange in the leaf.

In this article, we will learn about transpiration, its definition, types, and its importance. Read on to find out more!

What is Transpiration?

The loss of water in the form of vapours from the living tissues of aerial parts of the plant is termed transpiration.

1. Most of the water absorbed by the plants is lost in the atmosphere. Less than \(5\%\) of water is utilized by the plants for their growth and development.
2. Transpiration is also basically an evaporation phenomenon. But it differs from the general process of evaporation.
3. Evaporation means loss of water vapour from the surface, but in transpiration, water passes through the epidermis through the stomata.

Types of Transpiration

Transpiration can take place through three main organs of plants, so transpiration is of three types:

I. Stomatal Transpiration: It is the loss of water vapour through stomata. It accounts for \(80-90\%\) of the total water loss from the plants.

Fig: Stomatal Transpiration

Fig: Transpiration

II. Cuticular Transpiration– Cuticle is the outer waxy covering of the leaves. If it is thin, then cuticular transpiration takes place. But if it is thick, then water vapour loss is significantly reduced. Up to \(20\%\) of total transpiration takes place through this process.
II. Lenticular Transpiration– Loss of water through lenticels (present in woody stems) is called lenticular transpiration.

Process of Transpiration

Inside the plant, water is transported through xylem vessels to each cell. The leaves absorb heat from the surrounding air. An increase in temperature causes evaporation of water from the cells of the leaves, which results in cooling of the surface of the parts of the plant and the surrounding environment. During this process, i.e. vapourisation, turgid cells of leaves lose water into the intercellular spaces. Water diffuses out from the intercellular spaces through stomata in the form of water vapour when the outside environment is dry with high temperatures.

Transpiration is regulated by the opening and closing of stomata. Although very little water is lost through open surfaces of leaves through cuticles. The opening and closing of stomata is guarded by guard cells surrounding stomata.

Transpiration is regulated by external and internal factors. External factors include atmospheric humidity, temperature, light, windy velocity, atmospheric pressure, available soil water, while internal factors include leaf area, its structure and age of plants.

Transpiration is a “necessary evil”. It is said so because although water is important for maintaining the life of a plant, a major amount of water is lost through transpiration because this loss has more beneficial effects than harmful effects. This loss of water may result in the drying and wilting of leaves, leading to the death of the plant. Still, this process of transpiration is necessary due to its several benefits, like this process is the essential driving force for the ascent of sap.

What are the Significances of Transpiration?

Following are the significance of transpiration:

I. Cooling Effect: Transpiration involves the evaporation of water, and we know that evaporation results in the cooling of the surface. So, transpiration leads to the cooling of the plant organs. High temperatures can denature the enzymes of the plant.

Fig: Cooling of Leaf Surface by Transpiration

II. Bringing water to the top of the plant: Transpiration helps in the ascent of sap. When transpiration takes place, water evaporates from the intercellular spaces of the leaves into the outer atmosphere through the stomata. Due to water loss, a negative hydrostatic pressure is created to draw water from the roots to the veins of the leaves. The negative tension is then gradually transmitted downwards. As a result, there is a continuous upward movement of the water column in the plant and lumen of tracheids and vessels of a xylem link to form a narrow tube and water rises in the narrow tube due to the force of surface tension through capillary action. This biological process is responsible for moving water to the top of tall trees; as water evaporates from the leaves, it creates a suction force at the top.

Fig: Transpiration

III. Absorption and upward translocation of mineral salts: Mineral salts are absorbed from the soil through roots and reach the xylem vessel. In the vessel, these minerals get mixed with water and are transported upward with the water to all parts of the plant. This translocation is also dependent on transpiration. More is the rate of transpiration; more is the absorption and upward translocation of minerals.

IV. Removal of excess water absorbed by plants: Excess water in the cells may clog the intercellular spaces of the leaves, so transpiration helps in the removal of excess water that is absorbed from the soil.

V. Distribution of water: Transpiration helps in the distribution of water all over the plant body.

VI. Optimum turgidity: This process maintains the cell turgidity of the plant, i.e., neither too turgidity is beneficial for the plant growth nor too shrank or flaccid cells, which results when water potential gets decreased or highly negative.

VII. Affects climate: Transpiration increases the moisture in the atmosphere and brings rain. Thus, forests contribute to bringing rain. Transpiration is one of the important steps in maintaining a water cycle.

Fig: Transpiration Contributes in Water Cycle

Summary

From the above discussion, we came to know about what transpiration is and its significance. Transpiration is nothing but an evaporation process taking place through stomata of leaves, cuticles or lenticels. As this process involves evaporation, it helps in cooling the surface of leaves. It is more when the temperature of the atmosphere is high and dry. It helps in the distribution of water and minerals throughout the plant body. This transpiration also maintains the water cycle. Although much water is lost through transpiration, it is important for the survival of plants, so it is a necessary evil.

FAQs

Q.1. What is the significance of transpiration in plants?
Ans: 1. Transpiration results in cooling of the surface of the plant body.
2. Transpiration creates a transpiration pull that results in more suction of water from the roots.
3. Transpiration removes excess water absorbed by plants.

Q.2. What is transpiration and its types?
Ans: The loss of water in the form of vapours from the living tissues of aerial parts of the plant is termed transpiration. Its types are stomatal transpiration, cuticular transpiration and lenticular transpiration.

Q.3. How do plants help in bringing rain?
Ans: Transpiration occurs in plants. This transpiration involves loss of water in the form of vapours which adds to the cloud formation and results in precipitation or rain.

Q.4. Is transpiration good or bad?
Ans: Transpiration is a necessary evil. Although it involves loss of water, it is important for the plant.

Q.5. Does transpiration occur at night?
Ans: Yes, transpiration occurs at night.

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