Transpiration

What is transpiration?

Transpiration in general, it is meant for exchange of gases or vaporization. In plants, it is the process of loss of water vapor through the pores present in the leaf called stomata.

What is the need to lose water from plants?

• The first need is to cool the leaf, one of the physical aspect of cooling is vaporization i.e., evaporative cooling. So, the plants lose water to cool themselves, otherwise it will dry due to high environmental temperature.
• The second need is to pull the water for photosynthesis. The loss of water in leaves or transpirated sites creates hydrostatic pressure. To balance the pressure created there, the pull of water in roots effected. The entry of water from the soil into the roots by the process called osmosis. Then, it diffuses into conductive tissue called xylem and it transported throughout the plant wherever it is needed.
• The pull of minerals also done by transpiration and it is transported through the conductive tissue called phloem.

Factors affecting transpiration:

• Light: When the intensity of light is high, the rate of transpiration is high and it becomes reduced when the intensity is low.
• Temperature: When the environmental temperature is more, it leads to more transpiration and becomes reduced when the temperature is low.
• Humidity: As we know already that diffusion becomes very easy when it moves through downhill gradient. Therefore, the increase of humidity leads to less transpiration rate and the decrease of humidity leads to high transpiration rate.
• Wind speed: It is another factor relating humidity, when the breeze is fast, the humidity near leaves becomes less, it leads to high transpiration rate and when there is no breeze, humidity near leaves becomes high, it leads to low transpiration rate.
• Soil water: It is very important factor because it is the source of water for the plants for photosynthesis as well as transpiration, so transpiration is highly affected by the presence or absence of soil water.