Guttation, how plants deal with too much water

Guttation, drop on leaves

Guttation is how plants expel excess water or nutrients through tiny openings on leaves and stems. and water content.

Key facts about guttation:

Common name – crying plant,
weeping leaves, teary plant, dewdrop
Type – plant physiological process

Occurrence – often
Observation time – early morning
Affects – houseplants & low-lying plants

This biological process enables plants to restore balance between their nutrient intake and needs.

Recently, science is realizing plants use guttation to communicate!

What is guttation?

Guttation definitionGuttation occurs when a plant oozes water and minerals out from perfectly healthy leaves, stems, and sometimes even flower petals.

It takes place when roots of a plant absorb more water than the plant actually needs.

Tiny, specialized cells on the surface of a leaf or stem are connected to veins and sap channels of the plant. This cluster of cells works as a nozzle. It releases water from the plant’s vascular system to the outside, forming drops that look like dewdrops.

This process where excess pressure is released from inside the plant is called guttation.

  • These nozzle-like cells are called hydathodes. They’re a special class of stomata. Stomata are bean-shaped cells that open up to let the plant breathe and transpire.
  • orchid guttationHydathodes are usually placed around the rim or tips of leaves, on the leaf surface, or at junctures between leaves and stems.
  • Less than 5 % of all water that goes in a plant is released through guttation. Nine tenths is from transpiration, a more powerful phenomenon.

About the term “Guttation”:

  • The verb to say this “guttate”, but it isn’t very common. Simply, variations like “guttation is observed” or “hydathodes exude/secrete/release” are used. “Guttant” is the fluid expelled.
  • It comes from latin “gutta” which means “drop”. An easy memory trick is to remember words in English like “gutter” and French “goutte” (also “drop”) and go from there.

To understand why plants developed guttation as they evolved, it helps to brush up the following:

  • how water is used in a plant.
  • techniques plants developed to move this water around, creating pressure.

Hydathode nozzles are one of the biological tools plants use to regulate pressure inside them.

How does a plant use water?

Water used to transport nutrients up and down the stems and leaves is called sap. But there are more uses of water in a plant than simply transportation! Here is a short list of how a plant uses water:

  • Nutrient transport from roots to leaves and vice-versa
  • Cells are full of water. On a microscopic level, this is where chemical reactions take place.
  • In some plants, water shapes the plant, such as the shy but rugged Mimosa pudica which closes when touched.
  • Some seed pods use water to eject seeds: when dry, they burst and project seeds far away. A typical example is the common Geranium.
  • On the surprising Ginkgo biloba, water fertilizes the seed: it carries the male pollen to the female ovum inside the hull to fertilize it.

Plants are under pressure

If ever you’ve opened a fresh coconut, you must have noticed that when the hull is slit, drilled or broken, coconut water spurts out. The pressure inside the coconut is higher than the pressure of the air around it. You can also see happen when slitting open a watermelon: the last few inches simply split open on their own.

Thanks to a combination of chemical reactions, tissue structure and cell components, a plant is able to control water in and around it.

  • Starchy stems help Dracaena resist drought. Starch captures water molecules and releases them when the weather is dry.
  • Capillarity helps many flowers pull water up from ground level. This is the basis for fun experiments with cut peonies or carnations absorbing dye up to their petals.

Guttation is one of the ways excess pressure is released. If not for this, the plant might burst at weak spots of veins and leaves!

When to find guttation on plants

On blades of grass, as on these iris leaves, sap guttates at the tips.First off, not all plants guttate. For those that do, there’s a chance of seeing guttation in the following situations:

Night-time and early morning

Plants breathe at night and still need sap to flow up and down the plant. Guttation takes over to force sap and water up when transpiration stops being effective.

    • Daytime breathing is powered by transpiration or “sweating”. In warm, dry air, water evaporates from leaves and creates a “vacuum” inside the plant.  This vacuum pulls nutrient-rich sap up.
    • At nighttime, evaporation and transpiration don’t work as well. The plant compensates by having the roots push water upwards. To do this, roots use chemicals to attract water from the surrounding soil.
    • This builds up pressure in the plant and sap and minerals are pushed up. It’s such a strong phenomenon that excess water needs to be released at the tip of leaves through guttation!

Days of high moisture and humidity

When the air is near or above 100% relative humidity, it’s impossible for a plant to sweat.

  • Even during daytime, guttation must take over to get sap circulating through the plant.

Excess moisture in the soil

It isn’t a common reaction, but guttation is one way of helping the plant evacuate excess water around roots. It’s a coping the plant uses to protect roots from rotting.

  • Some plants use gutation to drain soggy soil around them like the weeping willow tree. It’s doubly weeping!
  • Guttation isn’t necessarily a sign of over-watering.

Young plants

Seedlings and young plants tend to guttate more than older, more established plants.

Plant mechanisms similar to guttation

Gummosis and latex flow are similar to guttation in that fluids are also expelled from the plant through controlled interfaces.

  • Gummosis is mostly mentioned when a disease like canker triggers too much fluid release.
  • But it is also a perfectly natural phenomenon that also occurs in healthy plants.
  • When the environment changes too drastically, gummosis occurs to help the plant adjust. This happened to one reader’s Acacia dealbata trees.

Bleeding, resulting from a wound to the plant, is different.

Dew and dewdrops are something entirely different, but are also useful to plants. Plants can maximize dew without being responsible for creating it.

Read also:

Smart tip about guttation

Guttation can even reach the point where sap drips to the ground. It can leave hard-to-remove stains on almost every surface, indoors and out!

So hose it away outside, and wipe it up indoors.

Images: 123RF: Andriana Syvanych, CC BY 2.0: Maja Dumat, соннна тетеря, CC BY-NC 2.0: Martin LaBar, CC BY-SA 2.0: Cynthia Hollenberger; own work: Rosalyn & Gaspard Lorthiois