Guttation

I have no doubt I've seen this on plants and assumed it was deposition to dew from the atmosphere.

Guttation is the exudation of drops of internal liquid out of the tips or edges of leaves of some vascular plants, and also a number of fungi... 

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 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 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.

But note...

Girolami et al. (2009) found that guttation drops from corn plants germinated from neonicotinoid-coated seeds could contain amounts of insecticide consistently 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

Etymology from the Latin gutta for "a drop," and hence its incorporation into the medical term "guttate psoriasis":

"Gutter" is also derived from gutta, after passing through French and Middle English.  Found the word while doing a crossword puzzle.  You learn something every day.