Have you ever noticed how beautiful a leaf looks when a little droplet of liquid appear on the tips? It looks spectacular in every way and that’s why a lot of nature photographers are longing for them to take a beautiful picture. But this phenomenon has a scientific name: guttation.
The droplets in the picture above should not be confused with dew. Dew is just the moisture in the air that condensates all over the surface of leaves and grass in the morning or evening. These droplets are called ‘xylem’ and only occur due to a high moisture level in plants.
During the night plants close their stomata. Due to a stomata, a pore found in the epidermis of leaves, it’s possible to regulate gas control during the day. When there is a high soil moisture level, the roots of the plants will absorb the water. This is because the water potential of the roots is lower than the soil. The water will accumulate in the plant since the plant won’t be able to transpire at night as a result to the closed stomata. This will create a pressure in the root of the plant. This pressure forces some water to exude trough leaf tips, forming drops.
So guttation only occurs when transpiration is suppressed and the relative humidity is high, such as during the night. This process doesn’t take place in every plant. For example, trees are usually way to large. Only root pressure will not be enough to push the water from the roots to the tips of the leafs and cause guttation. Usually the process takes places in plans that are smaller then 3 feet, grasses, vines and some smaller shrubs.
The xylem that exudes is not pure water. It contains a variety of organic and inorganic compounds. These compounds contain mainly sugar, amino acids, proteins, potassium, mineral salts and even some enzymes. If the xylem at the tips dry out, the tips show white spots. This is called a guttation burn.
Sometimes the soil contains to much fertilizer. Due to guttation, the excess of nitrogen gets pushed out of the leafs which creates xylem with a high concentration of nitrogen. This causes fertilizer burns, as showed in the picture above. The only treatment is soaking the soil with water to flush out the excess nitrogen salts from the fertilizer. Fertilizer burns can be prevented by applying a deluted fertilizer or a controlled-release fertilizer.