Imagine walking through a park on a sunny day, and then stopping for a breath of fresh air. Then you turn to your right and see a giant tree spanning the tops of the skies. Suddenly a thought then crosses your mind .”How do these trees get water from their roots all the way to their leaves”. This beautiful process is called transpiration.

Get ready because we are about to unravel the mysteries of transpiration. How water moves from the roots to the leaves, its loss as vapor, and the importance of this process for plant survival and growth.

Transpiration is simply the movement of water throughout the plant i.e. the movement of the water up and down the plant, and the evaporation of the water in the plant.

• Phloem
• xylem
• Stomata
• Guard cells

Movement of water from roots to leaves

Once the water is in the roots it is transported up the plant through the xylem vessels. These vessels are like pipes that carry water wherever needed in the plant. Something to note is that the xylem only carries water in one direction from the roots to wherever it is needed but never back down. 

Capillary action causes water to move upward in the xylem vessels due to capillary action, this is the ability of water to flow in narrow spaces without the help of other forces like gravity. The water is also able to move up the plant through a process called the transpirational pull.

Transpiration in leaves

Stomata are the pores on the leaf that open and close, allowing water to enter and leave. They are found on the backside of a leaf. They are like guard men who open and close, regulating the amount of water lost through transpiration. 

Evaporation, when the stomata are open water vapor escapes easily into the air. When one molecule of water escapes it creates a pulling force. Where one molecule is pulling another, and that one is pulling another, thereby creating a suction force that pulls the water up the xylem. through the process called transpirational pull.

factors affecting transpiration

Transpiration is caused by evaporation therefore naturally the factors that affect evaporation affect transpiration. These include:

• Humidity: when the amount of water molecules outside the plant is less (humidity is low) this will cause the water vapor to diffuse into the air more rapidly. Therefore the rate of transpiration will increase, and vice versa.
• Temperature: as the temperature of the surroundings increases, evaporation will increase and thus transpiration. This is as long as all the internal factors stay the same.  
• Wind: wind can reduce the humidity around the leaf, by removing the humid air around the leaf thereby allowing for more water vapor to escape. However, if there is a strong wind the stomata may close because it has lost too much water.
• Light: causes the stomata to open, the more light the wider the stomata will open. Thus causing more transpiration to occur on a hot day. Therefore cooling the plant.  

In summary, transpiration is a vital process for plants, which involves the movement of water from the roots to the leaves, then evaporates into the atmosphere. This process is essential for nutrient transport, cooling, and maintaining the plant’s structure.