Guttation

Guttation may look like dew, but it is actually a plant’s way of getting rid of excess water.

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Photo of guttation on strawberry leaf by NoahElhardt (Wikipedia)

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Dew normally accumulates on plant surfaces when there is enough moisture in the air and temperature differences that create different rates of evaporation and condensation. Guttation is closer to sweating.


Under normal conditions, plants close the tiny holes, or stoma, found on the underside of leaves. These stomata are used in respiration. When there is too much water in the soil, water pressure builds up in the roots. This forces xylem sap out of tiny leaf edge structures called hydathodes. When this xylem sap dries on a leaf, it often leaves a white crust. This crust is mostly sugars and potassium.


Research has shown that corn seeds treated with neonicotinoids create guttation drops that contain active ingredients that have insecticidal properties. These chemicals may be partly responsible for colony collapse disorder. As bees drink these sugary droplets, they are poisoned and die within minutes.