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 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 help in evaporation by carrying away water vapour, which helps in the formation of more water vapour. Hence, wind speed also affects the rate of evaporation.
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 –
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The main differences between evaporation and transpiration have been illustrated in the table below
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 in 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.
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1. Which Part of the Plant Evaporates Water?
Ans. Leaves have tiny pores called stomata through which plants evaporate water.
2. Name the External Factors that Affect the Transpiration Process?
Ans. External factors that affect the transpiration process are humidity, sunlight, amount of light available, temperature and wind.
3. What is the Difference Between Transpiration and Respiration?
Ans. The process through which water is circulated to different parts of a plant is known as transpiration. Whereas, respiration is the process where plants convert carbon dioxide to oxygen.