An example of
guttation, the appearance of drops of
xylem sap on the tips or edges of leaves of some
vascular plants, on an
Equisetum. At night,
transpiration usually does not occur because most plants have their
stomata closed. When there is a high
soil moisture level, water will enter plant roots, because the
water potential of the roots is lower than in the soil solution. The water will accumulate in the plant creating a slight
root pressure. The root pressure forces some water to exude through special
leaf tip or edge structures,
hydathodes, forming drops. Guttation is not to be confused with
dew, which
condenses from the atmosphere onto the plant surface.
Photo credit: Luc Viatour