• Guttation is the appearance of drops
of xylem sap on the tips or edges of
leaves of some vascular plants, such as
grasses. Guttation is not to be confused
with dew, which condenses from the
atmosphere onto the plant surface
Secretion of water on to the surface of
leaves through specialized pores, or
What is the main cause of guttation in plants?
• The main cause of guttation in plants is
root pressure,during night when root
pressure is high sometimes den due to
this pressure watery drops ooze out
with the assistance of special
structures which help in guttation
called the hydathodes.
• Transpiration is a process similar to
evaporation. It is a part of the water cycle, and
it is the loss of water vapor from parts of plants
(similar to sweating), especially in leaves but
also in stems, flowers and roots. Leaf surfaces
are dotted with openings which are collectively
called stomata, and in most plants they are
more numerous on the undersides of the
foliage. The stomata are bordered by guard
cells that open and close the pore. Leaf
transpiration occurs through stomata.
The differences between guttation and transpiration
1.Takes place through cuticle, lenticel
1.Takes place through hydathodes
2.It usually occurs in the day
2. It usually occurs in the night
3. Water lost in the form of water vapour 3. Water lost in the form of droplets
4. The water lost is pure
4.Guttation droplets contain organic and inorganic
5. It gives a cooling effect
6. Its benefial to plants as its maintains
body tempreture by cooling effects.
7.Occure during dry day
It does not give a cooling effect.
6. Its less significant to ;plant and some
time causes injury to plant by deposition
to of salts on the leaf tips after
7.ocuure during humid periods .
(Moisture loss is a pull due to evaporation) Evaporation of
water through stomata.
Loss of moisture from leaves and stems. Occurs usually during
the day. Stomata are on the underside of leaves 90% of moisture
loss is through Transpiration.
Guttation Shown is a compound leaf of strawberry
A hydathode is a type of secretory tissue in
leaves, usually of Angiosperms, that secretes
water through pores in the epidermis or
margin of leaves, typically at the tip of a
marginal tooth or serration.
They probably evolved from modified
stomata. It is involved in guttation, where
water is released from the top in order to
transport the nutrients in the water from the
roots to the leaves. Hydathodes are
connected to the plant vascular system by a
Figure (a) Nasturtium leaf showing guttation at the margin of leaf
(b) A vertical section of a leaf showing hydathode.
• In botany a stoma (also stomate; plural stomata) is a pore,
found in the leaf and stem epidermis that is used for gas
exchange. The pore is bordered by a pair of specialized
parenchyma cells known as guard cells that are responsible for
regulating the size of the opening. The term stoma is also used
collectively to refer to an entire stomatal complex, both the
pore itself and its accompanying guard cells. Air containing
carbon dioxide and oxygen enters the plant through these
openings where it is used in photosynthesis and respiration,
respectively. Oxygen produced by photosynthesis in the
spongy layer cells (parenchyma cells with pectin) of the leaf
interior exits through these same openings. Also, water vapor
is released into the atmosphere through these pores in a
process called transpiration.
Differences between stomata &Hydathodes
1.Occure in epiderm of leaves ,young
1.Occure at the tip or margin of leves
that grown in moist shady place .
2.Stomatal aperture is guarded by two
kidney shaped guard cells.
2.Aperture of hydathodes is surround
by a ring of cuticularized cells
3.The two guard cells are generally
surrounded by subsidiary cell.
3.Subsidary cells are absent
4.Opening and closing of the stomatal
aperture is regulated by guard cells .
4.Hydathode pores remain always open
5.These are involved in transpiration
and exchange of gases .
5.These are involved guttation .
Hydathodes may be active or passive
1-Active Hydathodes are specialized
epidermal cells which do not have a cuticle
on the outside and are not connected
directly with vascular strand directly.
2-Passive Hydathode comprises loosely
arranged ,colourless and parenchymatous
cells known as epithem.it lies inside the leaf
below the vein end.
• Guttation fluid may contain a variety of
organic and inorganic compounds, mainly
sugars, and mineral nutrients, and potassium.
On drying, a white crust remains on the leaf
• The water that is lost in this process is not pure
but contains minerals, , organic acids, sugars
and even enzymes. The estimation of solutes
lost in this process, reveal that certain plants
loose about 200-500 mg of solutes per liter of
Guttation fluid contain various and
The guttation fluid may rill off,evaporate, or
Guttation play a role in tip burn of leaves.
Guttation fluid as its easly collectable
sollutions can be used in production of
• If high levels of nitrogen appear in the
fluid, it is a sign of fertilizer burn
.Excess nitrogen must be leached from
the soil by addition of large quantities
of water. This may result in water
pollution, but is the best way to restore
Fertilizer burn on a leaf
MECHANISM OF GUTTATION
• Under certain conditions like soil flooded
with overnight rain water and with high
relative humidity of the day atmosphere, the
root system of some plants like tomato,
potato, etc., absorb excess of water by active
uptake. As a result, hydrostatic pressure
develops in the root system which actually
pushes water upwards. So the water along
with other soluble components of the cells
is forced out of the xylem elements located
into Epithem tissue.
• As result, the space behind the water
stomata gets filled with the water and with
more root pressure operating; the liquid is
virtually pushed out of the pore, where the
resistance. Probably transfer cells may also
help in the retrieval of minerals and other
components from the xylem elements and
secreting out along with water.
• However, it has been speculated that active
hydathodes may directly secrete the
minerals and organic acids out of the
passive stomata. Such active secretion of
the above said substances creates
a diffusion gradient and water is just
withdrawn from the cells into exterior
surface so guttation takes place. In spite of
the borderline between active and passive
mechanisms of guttation is not much, the
concepts are attractive.
The injuries of concentrated gutted solution
are related to three kinds of casual bases.
• First, injuries are connected with loss and
depletion of usual amounts of vital nutrient
accumulation and concentration of guttation
products on localized areas of the plants.
• Finally, the entrance of various foreign agents
and pathogen causes injuries since they go
through water pore into the hydathodes during
active guttation periods.
• Chlorosis and necrosis, two guttation injury
symptoms, are usually observed on leaves
whose injuries are generally caused by direct
action of concentrated guttation solution and
The condition where the process of
• 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, hydathodes,
forming drops. Root pressure provides the
impetus for this flow, rather than
Why Does Guttation Take Place at Night?
The conditions must be right for guttation to
occur. Transpiration stops at night when the
stomata on leaves close. Water in the soil is
absorbed by the roots of vascular plants by
osmosis when the water potential in the
roots is lower than the water potential in
the soil. Root pressure forces the water up
through the roots into the stems and leaves
Gutation on grass, photographed
soon after sunrise
The related studies regarding to guttation
• Table 1- following show that some
the composition of
guttation fluid from Rye, Wheat, and Barley
Seedlings it show that total sugar content is
about equal in rye and barley fluids, but
lower in xvheat. Glucose is the principal
sugar component of the rye and barley
fluids and galactose highest in wheat. Most
of the amino acid in all 3 fluids is aspartic
acid or asparagine.
Barley fluid is far higher than the other 2 in
total amino acids, with wheat the lowest.
Most inorganic elements are found to be
highest in barley and lowest in wlheat, with
the exception of iron where rye is highest and
barley lowest. Barley fluid is highest in
choline, paminobeuizoic acid. thiamine, and
uracil, while rye is highest in inositol and
pyridoxine. Wheat is mutch lower than the
other 2 in choline and inositol.
Advantages and disadvantages of guttation
• The significance of guttation is not clear. It is of
less importance to plants. Sometimes it may
cause injury to leaf margins by salt deposits
which is left by evaporation of guttation water.
The salt deposits at the margin of pore of
hydathode may plasmolyse and kill the
entering pathogenic bacteria and fungi. the
process of guttation important nutrients and
water may be lost,which may in turn lead to the
dehydration and wilting of the plant.
Condition ocuring guttation
Guttation depend on many enviromental
conditions among these factors that favor
guttation are high water absorption ,high
root pressure ,and reduced transpiration .
The wind velocity.
soil moisture stress, as external factors,
played dominant roles in the regulation of