Hydathode

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A section of hydathode in the leaf of Primula sinensis (Brockhaus and Efron Encyclopedic Dictionary)

A hydathode is a type of pore, commonly found in

water hyacinth, rose, balsam
, 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, and represent modified bundle-ends. These cells (called epithem cells[3]) 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, in which positive xylem pressure (due to root pressure) causes liquid to exude from the pores.[4] 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.

Hydathodes are of two types:

  1. passive hydathodes, formed when a leaf vein terminates in an epithem (an area of thin-walled parenchyma).
  2. active hydathodes, formed when epidermal cells lose water actively.

See also

References

  1. doi:10.1111/j.1469-8137.1952.tb06121.x
    .
  2. doi:10.1111/j.1365-2745.2012.01963.x
    .
  3. ISBN 978-0713126389
    .
  4. ISBN 9780878935659
    .

External links
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