Guttation

Guttation is the exudation of excess water, as visible liquid droplets, from the edges or tips of leaves - and crucially, unlike ordinary transpired vapour, this liquid is never pure water but a dilute solution that carries a number of other dissolved substances along with it. It occurs under conditions of high atmospheric humidity, when normal vapour-phase transpiration is greatly suppressed, while root pressure keeps building up regardless and continues to force water into the plant faster than it can be lost as vapour - the surplus is then exuded instead as liquid. This liquid escapes through hydathodes, pores resembling stomata that are typically found in plants growing in moist, shady habitats (grasses, tomato, potato, brinjal and Alocasia are commonly cited examples); each hydathode sits above a mass of loosely arranged cells with unusually large intercellular spaces, called the epithem, and …