Question

What is hydathode?

Answer 1

A hydathode is a modified stomata. It is a type of pore, commonly found in angiosperms, that secretes water through pores in the epidermis of leaf margin, typically at the tip of a marginal tooth or serration.

Complete answer:
Hydathodes are glandular tissues composed of modified stomata. A hydathode is a more or less permanently open pore at a leaf margin or tip and consists of xylem vessels terminations. Its function is to eliminate excess water through a process called Guttation. Unfortunately, these openings may also allow bacteria and viruses to enter the leaf and infect the plant. It is commonly found in flowering plants (Angiosperm). They are also called water stomata. Hydathodes are commonly seen in water lettuce, water hyacinth, rose, balsam, and many other species.
Their function is to secrete water and ions in order to keep sap flow throughout the plant, they exude or secrete drops of water. In very humid regions air humidity can be so high that evapotranspiration through stomata becomes inefficient. As to keep sap flow from roots to leaves, the plant secretes it through hydathodes and this process is called guttation. Guttation happens at night when the soil is very moist and the roots absorb water. If there is too much water, root pressure causes the water to squeeze out of the plant and onto the tips of the leaves.

Note: Stomata and hydathodes are different. Stomata are present on the epidermis of leaf, young stem and floral parts. Hydathodes are present on the margins of the leaf where the vascular supply (vein) ends. Stomata are surrounded by a pair of specialized epidermal cells called Guard Cells. Hydathodes are surrounded by a ring of non-specialized cells.