Hydathode

A hydathode is a type of pore, commonly found in vascular plants,[1] that secretes water through pores in the epidermis or leaf margin, typically at the tip of a marginal tooth or serration.

Hydathodes occur in the leaves of submerged aquatic plants such as Ranunculus fluitans[2] as well as herbaceous plants of drier habitats such as Campanula rotundifolia.

Hydathodes are made of a group of living cells with numerous intercellular spaces filled with water, but few or no chloroplasts, and represent modified bundle-ends.

Hydathodes are involved in the process of guttation, in which positive xylem pressure (due to root pressure) causes liquid to exude from the pores.

[5] Some halophytes possess glandular trichomes that actively secrete salt in order to reduce the concentration of cytotoxic inorganic ions in their cytoplasm; this may lead to the formation of a white powdery substance on the surface of the leaf.