Table of Differences: Evaporation and Transpiration Processes
Evaporation and transpiration are both natural processes that help vapor formation through the loss of water. However, since they perform a similar function, it is often difficult to distinguish between evaporation and transpiration. Nevertheless, there are a lot of differences between these two processes.
The differences between evaporation and transpiration is discussed below -
Evaporation
Most of us are familiar with the concept of evaporation, whereby water is converted from its liquid state to a gaseous state. Evaporation usually takes place when solar energy heats water on surface water bodies like oceans, rivers and ponds.
Aside from water bodies, this process can also occur on other surfaces containing moisture such as soil and trees.
Evaporation is a continuous process; however, the rate of evaporation at a given time can vary based on several factors. These factors are as follows –
Temperature – High-temperature results in an increasing rate of evaporation and vice versa.
Humidity – High level of humidity means that the atmosphere already contains a significant amount of water droplets. Therefore, the rate of evaporation will be low.
The Surface Area of Water – The surface area of water is directly proportional to the rate of evaporation.
Wind – Wind helps in evaporation by carrying away water vapor, which helps in the formation of more water vapor. Hence, wind speed also affects the rate of evaporation.
Transpiration
The process through which plants absorb through their roots and then lose the excess water via stomata is known as transpiration.
This process is similar to perspiration in human beings, preventing plant tissues from overheating when the temperature is high. Along with water, plants also gather essential nutrients from the soil. These nutrients are then transported to different parts of a plant such as stems and leaves through transpiration.
Some External Factors Which Affect the Process of Transpiration Include –
Temperature – When the temperature is high, plants transpire more as water on the surface of leaves starts evaporating more quickly with increasing temperature.
Light – The stomata or tiny pores present in leaves detect presence and absence of light. The stomata open up widely when there is enough light, which facilitates both transpiration and photosynthesis.
Water Content in Soil – this is one of the most critical factors that affect transpiration in plants. A plant loses a large amount of water during transpiration. They make up for the loss of water by drawing water from the soil. Thus, if the soil does not contain adequate water, the stomata will close to preserve water leading to less photosynthesis.
The diagram below shows transpiration in plants –
(Image will be uploaded soon)
The main differences between evaporation and transpiration have been illustrated in the table below.
Difference Between Evaporation and Transpiration
Evapotranspiration
The total loss of water from the soil via evaporation and transpiration by plants is referred to as evapotranspiration. The concept of evapotranspiration is vital in relation to agriculture. It is because if evapotranspiration rates can be predicted ahead, one can ascertain how much irrigation is required for crops.
In addition to irrigation, evapotranspiration also affects soil moisture or the level of water that is in soil. The factors that determine evapotranspiration rate are – the crop type, soil type, temperature, soil moisture level, humidity and wind.
To learn more about transpiration and evaporation, or about any other topic of biology, go through our study materials today. You can also join our live online classes via Vedantu’s app.
Evaporation and Transpiration are natural processes that help to add water vapors to the environment. Now, we will learn how much water is transpired by plants.
Transpiration from plants is an invisible process. You cannot see when water transpired from the leaves. If you want to see transpiration in plants, you can put a plastic bag around the plant leaves. You can see transpired water on the inside of the bag. It is visible due to condensation. When plants are in the growing stage, the leaf will transpire more water than its weight.
Transpiration and Groundwater
At some places, the top layer of the soil where roots are found is located above the water table and is often wet. The soil above the water table is wet and when the rain comes the water infiltrates into the ground from the surface. But the water dries out without any precipitation. The water table is below the depth of plant roots, thus plants are dependent on water supplied by precipitation. If the water table is near the surface the roots can penetrate into the saturated zone below the water table and will help the plants to transpire water directly from the ground water. Thus, transpiration of groundwater results in depletion of the water table.
FAQs on Evaporation vs Transpiration: What Sets Them Apart?
1. What is the fundamental difference between evaporation and transpiration?
The fundamental difference is that evaporation is a purely physical process where water turns into vapour from any non-living, wet surface (like a lake). In contrast, transpiration is a vital physiological process where water vapour is lost specifically from the living tissues of plants, primarily through small pores on leaves called stomata.
2. How do evaporation and transpiration differ in terms of the type of process involved?
Evaporation is a simple physical process driven by environmental energy like heat and wind, requiring no biological activity. Transpiration, however, is a complex physico-biological process. While it involves the physical change of water to vapour, it is actively regulated by the plant's living structures, such as the opening and closing of stomata, making it a controlled, physiological function.
3. What environmental factors influence the rate of evaporation?
The rate of evaporation is influenced by several key environmental factors:
- Temperature: Higher temperatures provide more energy, increasing the rate of evaporation.
- Surface Area: A larger water surface area exposes more molecules to the air, speeding up evaporation.
- Humidity: High humidity, meaning more moisture is already in the air, slows down the rate of evaporation.
- Wind Speed: Faster winds carry away water vapour from the surface, accelerating the process.
4. What factors, both internal and external, control the rate of transpiration in plants?
The rate of transpiration is controlled by two sets of factors. External factors are similar to those for evaporation and include sunlight intensity, temperature, humidity, and wind. More importantly, internal (plant) factors also play a crucial role, such as the number and distribution of stomata, the plant's water status, and its overall canopy structure. These internal controls allow the plant to regulate its water loss.
5. Why is transpiration often described as a 'necessary evil' for plants?
Transpiration is called a 'necessary evil' because of a critical trade-off. It is necessary for creating the 'transpirational pull' that draws water and essential minerals from the roots up to the leaves and for cooling the plant surface. However, it is also an evil because the plant loses a significant amount of water (over 97% of absorbed water), which can lead to wilting and severe water stress, especially in dry or hot conditions.
6. Is transpiration just a special type of evaporation from plants?
This is a common misconception. While transpiration involves evaporation, it is not just a special type. The key difference is regulation. Evaporation is an uncontrolled physical process from a surface. Transpiration is a biologically controlled process where plants can manage water loss by opening or closing their stomata in response to environmental cues like light and water availability. This control is absent in simple evaporation.
7. What is evapotranspiration, and how does it relate to both these processes?
Evapotranspiration is a combined term used in hydrology and ecology to describe the total amount of water transferred from the land to the atmosphere. It is the sum of water lost through evaporation from the soil and other surfaces, and water lost through transpiration from plants. It provides a complete picture of water loss from an ecosystem.
8. How is the water lost in transpiration different from the water lost in guttation?
The form of water lost is the primary difference. In transpiration, water is lost as water vapour through the stomata. In guttation, water is exuded as liquid droplets of xylem sap through special pores called hydathodes. Furthermore, transpiration occurs mainly during the day, whereas guttation typically happens at night when humidity is high and transpiration is low.
9. What is the main difference between transpiration and respiration in plants?
The main difference lies in their purpose and the substances exchanged. Transpiration is the loss of water vapour from plants, which primarily drives water transport and cools the plant. Respiration is a metabolic process that breaks down glucose to release energy for the plant's survival; it consumes oxygen and releases carbon dioxide.
10. How does understanding the difference between evaporation and transpiration apply to agriculture?
This understanding is vital for water-efficient farming. Farmers can take measures to reduce water loss from both processes. For example, they can reduce evaporation from the soil by using mulch. To manage transpiration, they can use anti-transpirant sprays or choose crop varieties with lower transpiration rates for arid regions. This helps in conserving water and improving crop yields.
