A secretory structure that removes water from the interior of a leaf and deposits it on the surface. This process is known as * guttation and often occurs during damp humid nights when water absorption is high but transpiration is minimal. In some plants, e.g. runner bean, the hydathodes are glandular hairs and water is exuded by active secretion, while in others they are water pores and exudation is passive, the water being forced out by hydrostatic pressure. Both types of hydathode are usually situated at vein endings. Water pores are generally incompletely differentiated stomata and in certain plants, e.g. sea lavenders (Limonium), function as salt glands. See also gland. |
