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What is Transpiration

What is Transpiration

Plants are responsible for 10% of the water vapor present in the atmosphere. An average oak tree transpires approximately 40,000 gallon water in a year. This is because of the process of transpiration. Find out what is transpiration, when it takes place and what is its importance.
Niharika Arya
Green leaf with breathing cells stomata
Transpiration is a process of emission of water from the plant with the help of stomata. Stomata are small openings or pores which are present on the aerial part of the plants like leaves, stem, flowers, etc. But the leaves constitute major portion of stomata.

What is the Process of Transpiration?
Before the process of transpiration, there are a series of processes for a plant to undergo. After completing all these processes, transpiration takes place. Following are the steps which will help you understand the complete process.
  • Plant takes water, dissolved essential plant nutrients and minerals from the soil with the help of the roots through the process of osmosis.
  • Due to the lower water pressure in the leaves and upper part of the plants, the water travels from the roots to the upper parts through xylem.
  • The water and the other minerals get mixed with the CO2 and chlorophyll in the leaves and prepare food with the help of sunlight.
  • Here, the process of Transpiration starts. When the water reaches the leaves, it is brought to the surface of the leaves with the help of stomata. Stomata help in the exchange of gases, that is, they take in CO2 and give out O2 in the atmosphere.
Role of Stomata
Stomata plays the lead role in conducting the process of transpiration. Stomata has two guard cells which are responsible for their opening and closing. The rate of transpiration is directly proportional to the opening and number of stomata. In the daytime, the stomata is open. As the sun is not present at night, the cells remain close at that part of the time. The stomata release water in the atmosphere, which is then broken down into oxygen and hydrogen. In return, the atmosphere gives carbon-dioxide to the plant to complete its process of photosynthesis.

The number of stomata may vary in different plants. In xerophytes the number of stomata will be less as compared to the other plants. This reduces the water loss and helps the plant to survive in adverse conditions. The plant may also close its leaves if there is excess sunlight, to save the water from transpiration.

Factors Affecting Transpiration
There are many environmental and internal factors which affect the rate of transpiration. Following are some of them.
  • High temperature may result in the opening of stomata and hence, increases the transpiration.
  • In the normal procedure, plant gets water from the soil. If plant does not get water from the soil, the stomata remains closed.
  • The rate of humidity is inversely proportional to the rate of transpiration. That means when humidity increases, transpiration decreases.
  • Light increases the temperature which in turn, increases transpiration.
  • Transpiration increases with the wind but high winds result in the closing of stomata which reduces transpiration.
  • Leaf structure, type of stomata, root and shoot ratio, etc., may also affect the rate of transpiration.
Importance of Transpiration
Transpiration is a very important process not only for the plant but also for the environment. Following are some of the significant roles it plays.
  • Transpiration helps in the process of photosynthesis and exchange of gases.
  • In the water cycle, it plays a major role as approximately 10% of total water which is present in the atmosphere is because of the transpiration process.
  • It helps in maintaining the level of CO2 and O2.
Excess cutting of trees has resulted in the imbalance in the nature's cycle and has caused global warming. So, to save our environment and life, we need to plant trees and help them flourish.
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