- Transpiration is the evaporation of water from cell surfaces and its loss through the anatomical structures of the plant (stomata, lenticels and cuticles).
- The total water loss by transpiration may be very great.
- The daily water loss of large, well watered tropical tress may run as high as 500 litres.
- A corn plant may loose 3 to 4 litres of water per day. [Source: https://www.agricoachingdelhi.in/]
- Whereas a tree sized desert cactus may loose water less than 25 ml per day.
- In general about 99 per cent of water absorbed by a plant during the growth is lost in transpiration (necessary evil). [BHU 2017]
- Water lost by a growing field of corn would be about 8-11 inches of water per acre during the growing season.
- Transpiration is mostly taking place through the stomata.
- Although large quantities of water are absorbed by plant from the soil, only a small amount is utilized. The excess of water is lost from the aerial parts of plants in the form of water vapour and this process is called as transpiration. [Source: https://www.agricoachingdelhi.in/]
- Nearly >95 per cent of water absorbed by the plants is lost through transpiration and only <5 per cent is utilized by the plant.
Types of transpiration
- In general, there are 3 types of transpiration i.e. stomatal, cuticular and lenticular transpirations.
- 1. Stomatal transpiration
- Most of the transpiration takes place through stomata.
- Stomata are usually confined in more numbers on the lower sides of the leaves.
- In most of the monocots, they are equally distributed on both sides of leaves, while in aquatic plants, stomata are present on the upper surface of the floating leaves.
- Stomatal transpiration accounts for 80-90 per cent of the total water loss from the plants. [JRF 2016] [Source: https://www.agricoachingdelhi.in/]
- 2. Cuticular transpiration
- The loss of water through the impervious cuticle is called as cuticular transpiration.
- It may contribute a maximum of about 10 ten per cent of the total transpiration.
- 3. Lenticular transpiration
- The loss of water through the lenticels of woody stems is called as lenticular transpiration.
- It accounts for about 0.1 per cent of the total transpirational loss of water.
- 1. Osmotic diffusion of water in the leaf, from xylem to intercellular space above the stomata through the mesophyll cells. [Source: https://www.agricoachingdelhi.in/]
- 2. Opening and closing of stomata (stomatal movement).
- 3. Simple diffusion of water vapour from intercellular spaces to outer atmosphere
