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A hydathode is a type of pore, commonly found in angiosperms, that secretes water through
hydathode physiology
Plant anatomy {{botany-stub
A hydathode is a type of pore, commonly found in angiosperms, that secretes water through pore
Pore may refer to:
Biology Animal biology and microbiology
* Sweat pore, an anatomical structure of the skin of humans (and other mammals) used for secretion of sweat
* Hair follicle, an anatomical structure of the skin of humans (and other m ...
s 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'' as well as herbaceous plants of drier habitats such as ''Campanula rotundifolia
''Campanula rotundifolia'', the harebell, Scottish bluebell, or bluebell of Scotland, is a species of flowering plant in the bellflower family Campanulaceae. This herbaceous perennial is found throughout the temperate regions of the northern hemi ...
''. They are connected to the plant vascular system by a vascular bundle. Hydathodes are commonly seen in water lettuce
''Pistia'' is a genus of aquatic plants in the arum family, Araceae. It is the sole genus in the tribe ''Pistieae'' which reflects its systematic isolation within the family. The single species it comprises, ''Pistia stratiotes'', is often cal ...
, water hyacinth
''Pontederia crassipes'' (formerly ''Eichhornia crassipes''), commonly known as common water hyacinth is an aquatic plant native to South America, naturalized throughout the world, and often invasive outside its native range.rose
A rose is either a woody perennial flowering plant of the genus ''Rosa'' (), in the family Rosaceae (), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be ...
, balsam
Balsam is the resinous exudate (or sap) which forms on certain kinds of trees and shrubs. Balsam (from Latin balsamum "gum of the balsam tree", ultimately from Semitic, Aramaic ''busma'', Arabic ''balsam'' and Hebrew ''basam'', "spice", "perfume ...
, and many other species.
Hydathodes are made of a group of living cells with numerous intercellular spaces filled with water, but few or no chloroplasts
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in ...
, and represent modified bundle-ends. These cells (called ''epithem cells'') open out into one or more sub-epidermal chambers. These, in turn, communicate with the exterior through an open water stoma or open pore. The water stoma structurally resembles an ordinary stoma, but is usually larger and has lost the power of movement.
Hydathodes are involved in the process of guttation
Guttation is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses, and a number of fungi, which are not plants but were previously categorized as such and studied as part of botany. Guttation ...
, in which positive xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...
pressure (due to root pressure
Root pressure is the transverse osmotic pressure within the cells of a root system that causes sap to rise through a plant stem to the leaves.
Root pressure occurs in the xylem of some vascular plants when the soil moisture level is high either ...
) causes liquid to exude from the pores. Some halophyte
A halophyte is a salt-tolerant plant that grows in soil or waters of high salinity, coming into contact with saline water through its roots or by salt spray, such as in saline semi-deserts, mangrove swamps, marshes and sloughs and seashores. Th ...
s possess glandular trichome
Trichomes (); ) are fine outgrowths or appendages on plants, algae, lichens, and certain protists. They are of diverse structure and function. Examples are hairs, glandular hairs, scales, and papillae. A covering of any kind of hair on a p ...
s 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.
Hydathodes are of two types:
# passive hydathodes, formed when a leaf vein terminates in an epithem (an area of thin-walled parenchyma).
# active hydathodes, formed when epidermal cells lose water actively.
See also
*Transpiration
Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth ...
*Vascular plants
Vascular plants (), also called tracheophytes () or collectively Tracheophyta (), form a large group of land plants ( accepted known species) that have lignified tissues (the xylem) for conducting water and minerals throughout the plant. They ...
*Xylem
Xylem is one of the two types of transport tissue in vascular plants, the other being phloem. The basic function of xylem is to transport water from roots to stems and leaves, but it also transports nutrients. The word ''xylem'' is derived from ...
References
External links
hydathode physiology
Plant anatomy {{botany-stub