Dew on an Equisetum fluviatile Luc Viatour

Guttation is the exudation of drops of internal liquid out of the tips or edges of leaves of some

vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

s, and also a number of

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

. Ancient Latin gutta means "a drop of fluid", whence modern botany formed the word guttation to designate that a plant exudes drops of fluid onto the outer surface of the plant, when the source of the fluid is inside the plant. Guttation happens in a variety of plant species.

Process

At night,

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. It is a passive process that requires no energy expense by the plant. Transpiration also cools plants, c ...

usually does not occur, because most plants have their

stoma In botany, a stoma (: stomata, from Greek language, Greek ''στόμα'', "mouth"), also called a stomate (: stomates), is a pore found in the Epidermis (botany), epidermis of leaves, stems, and other organs, that controls the rate of gas exc ...

ta closed. When there is a high

soil moisture Soil moisture is the water content of the soil. It can be expressed in terms of volume or weight. Soil moisture measurement can be based on ''in situ'' probes (e.g., capacitance probes, neutron probes) or remote sensing methods. Water that enters ...

level, water will enter plant roots, because the

water potential Water potential is the potential energy of water per unit volume relative to pure water in reference conditions. Water potential quantifies the tendency of water to move from one area to another due to osmosis, gravity, mechanical pressure and mat ...

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 A leaf (: leaves) is a principal appendage of the plant stem, stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leav ...

tip or edge structures called hydathodes or water glands. Root pressure provides the impetus for this flow, rather than transpirational pull. Guttation is most noticeable when transpiration is suppressed and the relative humidity is high, such as during the night. Guttation formation in fungi is important for visual identification, but the process causing it is unknown. However, due to its association with stages of rapid growth in the life cycle of fungi, it has been hypothesized that during rapid growth periods excess water produced by accelerated respiration is exuded.

Chemical content

Guttation fluid may contain a variety of organic and inorganic compounds, mainly sugars, and potassium. On drying, a white crust remains on the leaf surface. Girolami et al. (2009) found that guttation drops from corn plants germinated from neonicotinoid-coated seeds could contain amounts of

insecticide Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, i ...

consistently higher than 10 mg/L, and up to 200 mg/L for the

neonicotinoid Neonicotinoids (sometimes shortened to neonics ) are a class of neuro-active insecticides chemically similar to nicotine, developed by scientists at Royal Dutch Shell, Shell and Bayer in the 1980s. Neonicotinoids are among the widest-used insecti ...

imidacloprid. Concentrations this high are near those of active ingredients applied in field sprays for pest control and sometimes even higher. It was found that when bees consume guttation drops collected from plants grown from neonicotinoid-coated seeds, they die within a few minutes.

Nitrogen levels

If high levels of nitrogen appear in the fluid, it is a sign of fertilizer burn.

Nutrition

Guttation droplets are consumed by numerous insects of different orders, and is an important and highly reliable source of essential carbohydrates and proteins. Unlike nectar, guttation droplets are present in an ecosystem during the entire growing season.Plant guttation provides nutrient-rich food for insects - Journals
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References

{{Reflist Plant physiology

Process

Chemical content

Nitrogen levels

Nutrition

See also

References