Guttation is a natural process in which plants release small droplets of liquid from the tips or edges of their leaves. This phenomenon is often most visible in the morning, creating an appearance similar to dew. It is a normal physiological function that occurs in many vascular plants, including various grasses and some herbaceous species.
How Plants Release Water Droplets
Guttation begins with root pressure. When soil moisture levels are high, plant roots continue to absorb water and dissolved mineral ions, even when the plant is not actively losing water through its leaves. This continuous absorption creates a positive hydrostatic pressure within the plant’s vascular system, pushing water upward through specialized tissues called the xylem.
This water, containing various dissolved substances, travels through the xylem vessels to the leaves. At the leaf margins or tips, the water is exuded through unique structures called hydathodes. Unlike stomata, which open and close to regulate gas exchange and water vapor release, hydathodes are typically open pores that provide a pathway for the liquid to exit the plant. The liquid released during guttation is not pure water; it is a dilute solution of the plant’s xylem sap. This fluid can contain a variety of organic and inorganic compounds, including dissolved minerals like potassium, calcium, and magnesium, as well as sugars, amino acids, and even proteins.
Conditions Leading to Guttation and Its Importance
Guttation occurs under conditions that reduce the plant’s normal water loss through transpiration. These conditions often include high soil moisture, high humidity in the air, and cooler temperatures, which are frequently encountered during the night or early morning hours. When the air is already saturated with moisture, the evaporation of water vapor from leaf surfaces slows down considerably, allowing root pressure to build up without being offset by transpiration.
It is important to distinguish guttation from dew. Dew forms when atmospheric water vapor condenses onto cool surfaces, including plant leaves. In contrast, guttation involves water actively exuded from within the plant’s internal system. The droplets produced by guttation originate from the plant’s internal sap, while dew is external moisture.
Guttation serves several functions. It allows for the continued movement of water and nutrients through the plant’s vascular system even when transpiration rates are low. This process also helps dispose of excess water and accumulated solutes or minerals. By maintaining water flow and regulating internal pressure, guttation helps plants manage their water balance and supports cellular processes.