16 April 2015

This is NOT dew

Guttation is the exudation of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses. Guttation is not to be confused with dew, which condenses from the atmosphere onto the plant surface.

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 or water glands, forming drops.

Girolami et al. (2005) found that guttation drops from corn plants germinated from neonicotinoid-coated seeds could contain amounts of insecticide constantly higher than 10 mg/l, and up to 200 mg/l for the neonicotinoid 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. This phenomenon may be a factor in bee deaths and, consequently, colony collapse disorder (CCD).
Reposted in amended form from 2009.


  1. I would have posted this on FB, but the language is too multi-syllabic and complicated, I'm afraid that most of my friends would not understand what it means (except those who majored in chemistry or biology). Therefore the message doesn't get passed on to the average "joe."

    1. The last paragraph is what would interest most people, and most people would be able to get the gist of it: insecticides can get into the groundwater, and from there into plants which were not sprayed with insecticides and from there into bees, with serious consequences. You don't need to major in chemistry or biology to understand this. Don't underestimate your friends!

    2. Let's know how it went with your FB friends, Classof65!


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