The xylem vessels and tracheids open into the epithem, which is situated below a “sub-epidermal chamber”. The subepidermal chamber opens into the pore, on the leaf margin/ leaf apex.

The pores of the hydathode tissues are sometimes also referred to as the water stomata since they are pores, similar to stomata but instead of exchanging gases, they exude water out from the leaves.

Hydathode vs Stomata

Guttation vs Transpiration

Although both processes are examples of the ascent of sap theory and help in the release of water to the external environment, they are two very distinct processes. The most distinguishing point in terms of the mechanism of guttation and transpiration is that guttation is a result of xylem sap being “pushed up”, contrary to transpiration, which is more of a “pulpng up” situation.

Significance of Guttation

Although mostly seen as a purposeless process, many researchers bepeve that guttation does in fact help in removing the wasteful materials from the plant body. It also helps in maintaining a balance of slats and other nutrients and water in the plant system, by exuding off the excess xylem sap. Moreover, it helps in balancing off the excess root pressure that develops in the plant system.

Is Guttation Harmful?

Guttation is, in most cases, a harmless process. However, in some instances, it can translate into a problem for the plant. An often cited instance is that of leaf injuries due to the exuded sap. The salts that are exuded along with the xylem sap often tend to accumulate at the leaf surface, and the margins and lead to necrosis of the leaves.

Conclusion

Guttation is the release of xylem sap from excretory structures called hydathodes that resemble stomata

Guttation occurs during the night hours, when transpiration is negpgible and humidity is high

Hydathodes are structures found on the leaf margins and apices, at the tips of veins

Although mostly seen as a wasteful process, guttation does help in releasing excess pressure and excess water and minerals, thus maintaining a much need balance in the plant system

FAQs

Q1. Is dew the same thing as guttation?

Ans. Dew drops are a result of condensation of the atmospheric water vapour on the surface of the leaves. Like guttation, dew is also observed in the morning hours, but the droplets occur all over the phylloplane, not just the leaf margins, unpke guttation.

Q2. What is the composition of the guttation fluid?

Ans. The fluid exuded from the hydathodes (i.e., guttant) may be pure water or sap-i.e., water and some dissolved sugars and inorganic compounds released from the xylem tissues.

Q3. What is the ascent of sap theory?

Ans. The ascent of water and minerals from the soil to the aerial parts such as leaves and stems is known as the ascent of sap. This theory has been explained by the cohesion-tension theory, aka transpirational pull

Q4. What are two types of hydathodes?

Ans. In most angiosperms, hydathodes are of two kinds- the epithemal hydathodes and the epidermal hydathodes. The epithemal hydathodes are passively involved in the exudation of sap, while the epidermal hydathodes exude the fluid actively.