Plants suck water from soil with the help of roots for metabolic reactions and it's a continuous process. Only a small amount of water is used by plants and the remaining water is lost by transpiration. The water is lost in the form of water vapour. Transpiration is the process of loss of water in the form of water vapour. Transpiration occurs mainly through stomata. Apart from these, it can happen through surfaces of leaves, aerial parts, flowers, and stems. Vascular plants like grass lose water in the form of water droplets from the tips or margin of the leaves. Both the process is important for plants. In this tutorial, we will learn about transpiration and guttation in depth.
As we already know plant does not use all the water that is absorbed by the roots. More than 95% of water is lost through transpiration. Transpiration is the process in which excess water of the plants is lost in the form of water vapour. A major portion of water is lost in transpiration through stomata. Depending on which transpiration occurs there are three types of transpiration. That can be described below −
Stomatal transpiration − Major portion of the water vapour diffuses out through the stomata is known as stomal transpiration. Almost 80-90% of the water is lost through stomatal transpiration.
Cuticular transpiration − In cuticular transpiration small amount of water is lost through cuticles from epidermal cells of the leaves.
Lenticular transpiration − In this type of transpiration, the loss of water happened through stems and fruits.
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Transpiration is affected by both external and internal factors which can be described below −
Temperature − Transpiration increases in case of high temperatures.
Light − Transpiration rates increases in presence of light.
Humidity − The transpiration rate will be decreased if the humidity is more.
Wind velocity − Transpiration rate is increased when wind speed is more.
Atmospheric pressure − The higher the pressure lower the transpiration rate.
The internal factors also affect the rate of transpiration. The root shoot ratio is one of the most important internal parameters which influence the rate of transpiration. The transpiration rate will increase with the increase of the root shoot ratio. Apart from this structure and arrangements of leaves and the number of stomata affect the transpiration rate.
A lot of energy is required
Root absorbed more water from soil during transpiration which is not required by the plants at all.
Guttation is the process in which water is lost in the form of water droplets from the tips or margin of the leaves. Guttation has occurred through the specialized minute pores which are known as hydathodes. It is the most common phenomenon in vascular plants like grasses. In humid weather conditions the excess water present in the plant like grasses exudated in the form of liquid that is known as guttation. Dews are water droplets on the surface of the leaves of the grass seen in the early morning.
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Guttation is restricted to some herbaceous plants and woody plants.
The plants which show guttation grow in moist soil and the climate is warm and humid or when warm days are followed by cool nights.
The guttation process occurred when transpiration is suppressed and humidity is maximum that can be observed at night.
The liquid that is coming in the process of guttation is composed of organic and inorganic compounds mainly sugar and potassium.
Root pressure plays an important role in guttation,
Guttation occurred through the specialized structure known as hydathodes.
Hydathodes consist of loose parenchymatous cells called epithem. It is located over the vascular strands and with the help of pores in the epidermal cells they communicated outside. Hydathodes are different from stomata.
| Transpiration | Guttation |
|---|---|
| Through stomata, lenticel, and cuticles | Through hydathodes |
| In the form of water vapour, water is lost | In the form of liquid, water is lost |
| It is not a secretion | It is a type of secretion |
| Occurs in day time | Occurs in the early morning or in the night time |
| Transpiration rate increases when the temperature is high | Guttation occurs when the temperature is low |
| Occurs almost all parts of the leaf | restrict to the margin of the leaf |
| It is regulated by opening and closing of stomata | It is not regulated as hydathodes do not have opening and closing mechanism, |
| Root pressure is not involved | Root pressure is involved |
Transpiration is an important phenomenon of plants. In this process, the plants diffuse out the excess water in the form of water vapour. Transpiration can occur through stomata, lenticels, and cuticles and occurs only in the daytime. While in guttation loss of water in the form of liquid through hydathodes. Guttation can be seen in herbaceous plants and some woody plants, which occur in the early morning and night. Both transpiration and guttation removal of water from plants is a permanent process and primarily occurs through leaves.
Q1. What is transpiration pull?
Ans. In transpiration pull, water is absorbed by the roots and transported to the leaves with the help of suction force. The leaves used the required amount of water in photosynthesis and excess water is exudated with the help of transpiration.
Q2. What is turgor pressure?
Ans. The fluid in the cell exerted the turgor pressure. This pressure exhibits pressure in the cell membrane. It keeps the plants upright and makes tissue rigid. The loss of turgor pressure causes loss of water in plants as result the plant's leaves and stems become wilt. Additionally, it plays a vital role in the opening and closing of stomata.
Q3. How does the light affect rate of transpiration?
Ans. In the presence of light the rate of transpiration increases. In contrast transpiration rate decreases in the dark. Firstly, stomata are opening in the presence of light. As soon as stomata are opening wide, the interior cells come in contact with the outer environment. As a result transpiration rate increased in the bright sunlight. Secondly, because of bright sunlight, the temperature of the leaf increase and affect the rate of transpiration.
Q4. What is root pressure?
Ans. The force that is produced in the roots is known as root pressure. It helps push water upward into the xylem to the smaller height of the stem.
Q5. Why guttation is considered a secretion?
Ans. The tissue which is involved in guttation involves secretory tissue. That is the reason guttation is considered secretion.
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