Hydathode – Water Stomata
(Structure and Functions of Hydathodes)
What are Hydathodes?
Hydathodes are specialized pores (openings) particularly present on the leaf margins, which exudes or secretes drops of water. The exudation of water as drops from the tip or margin of the leaves is called guttation. The process of guttation is facilitated by the hydathodes.
Ø They are also called as Water Stomata because they structurally resemble stomata and they facilitate guttation (secretion of droplets of water from the pores of plants).
Ø Hydathodes are commonly found in Angiosperms, especially in grasses.
Ø They are also present in some other plants such as water hyacinth, balsam, roses, Hibiscus and rarely in some non-angiospermic plants.
Anatomy of Hydathodes
Ø Hydathode is a type of secretory tissue in leaves.
Ø They are made of a group of living thin walled parenchymatous cells in the leaf with numerous intercellular spaces. These cells are called epithem.
Ø The epithem lack chloroplasts (sometimes very few stomata are present).
Ø The epithem cells open into one or more sub-epidermal chambers.
Ø These sub-stomatal chambers communicate with the exterior through the specilized pores on the leaf epidermis called ‘water stoma’.
Ø Water stomata are the pores of the hydathode which facilitate guttation.
Ø They are usually located on the leaf margins.
Ø The water stomata resemble an ordinary stoma in shape and structure.
Ø However, the water stomata are larger than the ordinary stomata of leaves.
Ø Most importantly, the water stomata always stay opened since, they do not have opening and closing mechanism
Functions of Hydathode
Ø Facilitate guttation
Ø Also have an indirect role in ascent of sap
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