Adaptation in Plants To Reduce Transpiration: Definition

Adaptation in Plants to Reduce Transpiration: Water is the most vital constituent of all living tissues. It is an important constituent for plant tissues as well. Do you know how do plants absorb water? Plants absorb large amounts of water from the soil through its roots. But from that amount, only 2-5% of water is used by them, and the remaining amount of water is moved to leaves. And then, from leaves, the water vaporizes into the environment. Do you know what this process is called? This is known as transpiration.

Transpiration is an important process for the plant, but it is harmful to them also. Excessive loss of water from the plants through transpiration may lead to the death of plants. Hence, most plants, especially xerophytes, adopt various modes both morphologically and anatomically to reduce excessive transpiration. In this article, we are going to learn about the adaptations in plants to reduce transpiration.

What is Transpiration?

As we already know, transpiration is a process in which excessive water from tissues of the plants is lost through evaporation. Most of the transpiration takes place from the leaves of the plants as it provides a larger surface area than stem or other parts for transpiration to occur. transpiration is of 3 different types based on the plant surface. They are given as follows:
1. Stomatal Transpiration (occurs through stomata of leaves)
2. Cuticular Transpiration (occurs through cuticle)
3. Lenticular Transpiration (occurs through lenticels)

Fig: Transpiration

Learn About Shoot System

Need of Transpiration

Transpiration plays a very important role in the existence of plants. Plants absorb large amounts of water from the soil through roots. From that, only 2-5% of water is used for metabolic processes in the plant body. The remaining water is lost by transpiration. If the excess amount of water is not removed from the plant body, then it may lead to the death of the plant. Apart from this, transpiration also helps the plant to cool down. It also helps in pumping the water and minerals to the leaves of plants for photosynthesis. Indirectly it also maintains osmosis and helps to keep the plant’s cells rigid.

Why do Plants need to Reduce Transpiration?

Plants cannot survive in the absence of water. Global warming and climate change is leading to an increase in temperature. Drought is another extreme weather phenomenon that plants have to survive. In some areas, droughts are a very long dry period without rain. Hence, plants growing in such environments need to adapt features in order to survive and grow.

Plants lose most of their absorbed water due to transpiration. The rate of transpiration is high in areas with hot and dry climates. In simple terms, if the temperature is high, the transpiration rate will also be high. To survive in drought and dry conditions, plants need to reduce transpiration to limit their water loss. 

Plants are able to survive high temperatures and drought conditions due to their unique features. These characteristics can be internal or external adaptations. Such plants often look a little different from plants that live in areas with easily available water. These plants may have thick fleshy stems, smaller leaves, spines, waxy layers covering their leaves, etc. All of these features help plants to reduce loss of water through transpiration. Let us learn some examples of adaptations in plants in order to reduce the transpiration rate.

Adaptations to Reduce Transpiration

To reduce excessive loss of water from the plant body through transpiration, the plants have adopted both morphological and anatomical ways to reduce excessive transpiration. Some of these adaptations are explained below:

1. Sunken stomata: Stomata are small pores present on the surface of leaves. The maximum amount of transpiration happens through the stomata of leaves. So, in order to reduce the excessive transpiration, the size of stomata of leaves is reduced in some plants, or they are covered by thin hairs. This helps to block the pores and reduce the rate of transpiration. For example, Nerium.

Fig: Sunken Stomata

2. Fewer stomata: One of the other adaptations, in order to reduce excessive loss of water through transpiration, is that the leaves of certain plants have very less number of stomata. As the stomata of the leaves help in the transpiration process, so if the number of stomata will be less then, there will be less transpiration of water.

3. Narrow leaves: Small surface area of the leaf also helps to reduce transpiration rate. Leaves of some plants such as Nerium have narrow leaves to lower the rate of transpiration.

Fig: Spanish bayonet (Narrow-Leaf Plant)

4. Reduced exposed surface:  Hot and dry climates increase the loss of water to a great extent. In some of the plants, the leaves become wavy, coiled, rolled, or folded to reduce the surface area for transpiration. Areas that are not directly exposed show very low transpiration.

Fig: Prayer Plant (Wavy Leaves)

5. Loss of leaves: Mostly during winters, some plants lose their leaves to decrease the rate of transpiration. For example, deciduous trees shed the leaves twice a year according to the change of seasons.

Fig: Cherry tree

6. Thick cuticle: The leaves of some of the trees might be covered with thick cuticles to avoid excessive loss of water through transpiration from the stomata of leaves. For example, the leaves of banyan trees and banana trees have thick cuticles.

Fig: Banyan Leaves

7. Modification of leaves into spines or needles: In some of the plants, mostly in hotter regions, the level of transpiration is very high. So, the leaves of the plants in those regions are modified into spines or needles to reduce the surface area for transpiration. For example, cactus, pine, etc.

Fig: Cactus

Antitranspirant

These are materials or chemicals used to decrease the rate of transpiration artificially. These include certain chemicals such as colourless plastic resin, silicon oils, and low-viscosity waxes. When these anti-transpirants are sprayed on leaves, fruits, vegetables, and flowers, they form a thin film on the transpiring surface. This film is porous to respiratory gases but not to water. Phenyl Mercuric Acetate, Abscisic acid are a few examples of anti-transpirants.

Summary

Transpiration is a very important process in plants. It is the process in which excessive water is lost from the leaves of aerial plants through evaporation. There are three different types of transpiration- stomatal, cuticle, lenticular transpiration. Apart from the evaporation of water, transpiration plays an important role in cooling the trees, pumping water and important minerals from roots to leaves, keeping the plant cells turgid, etc.

Excessive transpiration in one plant may lead to the death of the plant. Hence, the plant has adapted in different ways, both morphologically as well as anatomically, to reduce the loss of water through transpiration. In some plants, leaves have become folded or coiled to reduce the surface area for transpiration. In some trees, leaves have thick and waxy cuticles on top. Leaves of some of the trees, mostly in hot regions, have been modified to spines and scales. In some of the plants, leaves have less stomata or no stomata.

FAQs About Adaptation in Plants To Reduce Transpiration

Let’s look at some of the commonly asked questions about transpiration:

Q.1. What is transpiration?
Ans: Transpiration is a process in which excessive water is evaporated from a plant through its leaves.

Q.2. How is transpiration helpful to plants?
Ans: Transpiration helps to remove the excess water from the plants. Apart from this, it also helps in cooling down the tree, pumping the water and minerals from roots to leaves, etc.

Q.3. Why is there adaptation in plants both anatomically and morphologically?
Ans: Plants adapt themselves according to their surrounding environment. There are many reasons behind the adaptation in plants, one of the many reasons for this adaptation is to reduce transpiration and to prevent plants from dying.

Q.4. What are examples of adaptation in plants to reduce transpiration?
Ans: Less number of stomata or no stomata in leaves of plants, modification of leaves into spines and needles, having a thick and waxy layer on leaf top, shedding of leaves two times a year, etc. are some of the examples of adaptation in plants to reduce transpiration.

Q.5. What kind of adaptation plants does have in hotter regions?
Ans: The plants of the hotter region (e.g., cactus) have modified leaves. The leaves of such plants have been modified into scales or spines to reduce the amount of water lost during transpiration.

PRACTICE QUESTIONS RELATED TO TRANSPIRATION

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