What is guttation?
Guttation occurs when a plant oozes water and minerals out from perfectly healthy leaves, stems, and sometimes even flower petals.
It takes place when roots of a plant absorb more water than the plant actually needs.
Tiny, specialized cells on the surface of a leaf or stem are connected to veins and sap channels of the plant. This cluster of cells works as a nozzle. It releases water from the plant's vascular system to the outside, forming drops that look like dewdrops.
This process where excess pressure is released from inside the plant is called guttation.
These nozzle-like cells are called hydathodes. They're a special class of stomata. Stomata are bean-shaped cells that open up to let the plant breathe and transpire.
Guttation on a phalenopsis orchid, resulting in black and white spots.
Hydathodes are usually placed around the rim or tips of leaves, on the leaf surface, or at junctures between leaves and stems.
Less than 5 % of all water that goes in a plant is released through guttation. Nine tenths is from transpiration, a more powerful phenomenon.