Guttation is the appearance of drops of xylem sap on the tips or edges of leaves of some vascular plants, such as grasses. Guttation isn't to be confused with dew, which condenses from the atmosphere onto the plant surface. Process At night, transpiration usually doesn't occur because most plants have their stomata closed. When there's 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 accumulat… (More on Guttation)