Question

What are hydathodes?

Answer 1

Hydathodes are a form of structure that are mainly present in higher plants and are a way for water to escape the plant, but not through the process of transpiration. They are found in both aquatic and dry habitats.

Complete answer:
- Hydathodes are a specialized form of secretory tissue. They are pores present on the margin of leaves where the supply from vascular tissue ends.
- Hydathodes are connected to the intercellular spaces and the xylem in angiosperms and release excess water through a process called guttation.
- They are made of cells known as epithem, which are thin-walled parenchymatous cells with numerous intercellular spaces filled with water, and few or no chloroplasts. Epithem cells further open into one or more sub-epidermal chambers. These chambers communicate with the external environment through the specialized pores known as water stomata.
- Hydathodes are involved in the process of guttation, in which positive xylem pressure (due to root pressure) forces the liquid to exude from these pores. This process is observed early in the morning, and the liquid is not dew.

Additional Information:
- Hydathodes are generally found at the tip of the marginal tooth or the serration.
- Hydathodes are found in both submerged aquatic plants and herbaceous plants in dry habitats.
- They are also known as water stomata because they structurally resemble stomata.
- Hydathodes are of two types, passive, where they are formed when a leaf vein terminates in an epithem, and active, formed when epidermal cells actively lose water.

Note: - Hydathodes have an indirect role in the ascent of sap.
- Water stomata are larger in size than actual stomata, and they always stay open and do not have any movement such as an opening or closing mechanism.
- Stomata aid in losing water in gaseous form while hydathodes aid in losing water in liquid form.