1. The document discusses various processes related to water movement in plants, including absorption, transpiration, and ascent of sap. 2. Key processes discussed include osmosis, which drives the absorption of water from the soil into root cells, and transpiration pull, where water lost through the stomata of leaves creates tension that pulls water up the stem. 3. The document examines several theories to explain the ascent of sap, with emphasis on the cohesion-tension theory where water forms a continuous column through the xylem and adhesion between water molecules allows them to be pulled upward against gravity.

1. Dr. Tushar Wankhede, MSc, Ph.D (NET,SET,GATE)
Associate Professor in Botany
Shri Shivaji Science College, Amravati
NAAC Reaccredited “A” with CGPA 3.13
College with Potential for Excellence (CPE)

3. 1. IMPORTANCE OF WATER
Water is a constituent of protoplasm & acts as a solvent.
Plants can absorb nutrients when these nutrients are
dissolved in water
Water is used for vital things like plants transpiration,
photosynthesis and for the germination of seeds, growth of
plant roots, and nutrition and multiplication.
Water forms over 90% of the plant body by green or fresh
weight basis.
Water regulates the temperature and cools the plant.
Water helps in the chemical, physical and biological
reaction in soil.
Physical Properties
Water has a high specific heat. ...
Water in a pure state has a neutral pH. ...
Water conducts heat more easily than any liquid
Chemical Properties
 H2O: two atoms hydrogen (H2) linked to one atom
oxygen
The atom electrons (particles with a negative charge)
establish links between themselves.

4. 2. IMBIBITION
The absorption of water
by the solid particles of
an adsorbent without
forming a solution is
called Imbibition.
In other words the
adsorption of water by
hydrophilic colloids is
known as Imbibition.
Imbibition is a seed's or
a plant's absorption of
water, a process that
causes swelling in some
plant cells and organs
(i) Imbibition is the first
step in the absorption of
water by the roots and
cells,
(ii) Imbibition of water
by cell walls helps to
keep the cells moist.
(iii) Imbibition pressure
is helpful in seed
germination, growth of
seedling through the soil,
ascent of sap in plants,

5. 3. DIFFUSION
Photosynthesis process makes entry of atmospheric CO2 through stomatal diffusion.
 The water moves from an area of high concentration (in the soil) to an area of lower
concentration (in the root hair cell). This is because root hair cells are partially
permeable.
 Diffusion is the movement of a substance from an area of high concentration to
an area of low concentration.
 As per second law of thermodynamics molecular movement takes place from
region of higher free energy (ΔG) to lower free energy. Diffusion happens
in liquids and gases because their particles move randomly from place to place.
 Diffusion is an important process for living things; it is how substances move in
and out of cells. In living things, substances move in and out of cells by diffusion

6. 4. PLASMOLYSIS
In many plant cells, the protoplasm may shrink completely away from
the cell wall and collect as a spherical mass in the centre or in one corner
of the cell. This phenomenon is called plasmolysis.
The point at which protoplast just begins to shrink away from the cell
wall is known as incipient plasmolysis & attaining spherical shape is
called evident plasmolysis.
It is a vital phenomenon as it explains the process of osmosis &
demonstrates the permeability of the cell wall and the semipermeable
nature of the protoplasm.
It helps to detect whether a particular cell is living or dead and Osmotic
pressure of a cell can be determined by plasmolytic method
This process in preservation of meat, jellies and other food stuffs, and
thereby prevents them from being destroyed by bacteria and fungi. It is
also involved in killing of weeds in lawns, orchards and agricultural fields
by chemical weedicides and also preventing the growth of plants in the
cracks of the walls.

7. 4. PLASMOLYSIS
A plasmolysed cell is transferred from hypertonic solution & to pure
water, it will slowly recover by the net inward movement of water (if
deplasmolysis, as it is sometimes called or inward movement of water, is
too rapid, it may result in the death of the cell due to sudden stretching of
protoplasm) subjecting the cell wall to a progressively imposed turgour
pressure & in consequence, reducing the suction pressure of the cell.

8. 5. Diffusion Pressure Deficit (or DPD).
The amount by which diffusion pressure of a solution is lower than its pure
solvent is known as Diffusion Pressure Deficit (or DPD). This term was first
coined by B.S. Meyer in the year 1938. Originally DPD was described as
suction pressure by Renner (1915). It is a reduction in the diffusion
pressure of water in solution or cell over its pure state due to the presence
of solutes in it and forces opposing diffusion.
Osmotic pressure
OP ( Ѱs):
1. It is potential pressure
that can develop till it
solution when it is
separated from pure
solvent by a
semipermeable
membrane.
2.OP or Ѱs causes
movement of water
across a semipermeable
membrane.
Turgour pressure
TP (Ѱp):
1. Its hydrostatic pressure
which develops in a
system due to osmotic
entry of solvent in it & It
develops only in a
confined system.
2. It is dependent upon
the amount of water
that enters a confined
system.. It provides
turgidity to the cells,
tissues and softer organs.
Wall Pressure (Ѱw):
1. It is the force exerted
by the wall against
expansion of osmotic
system.
2. Wall pressure occurs in
a confined system
3. Wall pressure prevents
bursting of cells and
limits expansion.
4. It is commonly equal
and opposite to TP or Ѱp

9. 5. Diffusion Pressure Deficit (or DPD).

10. 6. OSMOSIS
Osmosis can be defined as the the movement of a
solvent through a differentially permeable membrane
from a solution with high water concentration and low
solute concentration, to one with a low water
concentration and high solute concentration.
Plants rely on the nutrients and water in soil to survive.
In order for water uptake to occur, plant cells undergo
a process called osmosis. Because of osmosis role its
important in the survival of plant life.
Growing points of root remain turgid because of
osmosis and are thus, able to penetrate the soil
particles.
The resistance of plants to drought and frost is brought
about by osmotic pressure of their cells.

11. 6. OSMOSIS
The two types of osmosis are: i) Exosmosis. ii) Endosmosis.
Exosmosis: Movement of water molecules out of a cell when the cell is
placed in hypertonic solution.
Endosmosis: Movement of water molecules into the cell when the cell
is placed in hypotonic solution.

12. 7. Absorption of water in plants
Absorption of water in plants is a vital process for the growth
of plants and other metabolic activities through process of
osmosis by the whole plant body via the root hairs.
It’s a uptake of the capillary water by the root hairs of a
plant from the soil to the root xylem by many ways like
respiration, transpiration and osmosis.
Active absorption of water : need of metabolic energy by the
root cells to perform the metabolic activity like respiration.
Active absorption in plant occurs in two ways namely:
Osmotic and non-osmotic absorption of water.
Osmotic active absorption of water: the water absorption occurs
through osmosis where the water moves into the root xylem across
the concentration gradient of the root cell.
Non-osmotic active absorption of water:, the water absorption
occurs where the water enters the cell from the soil against the
concentration gradient of the cell.

13. 7. Absorption of water in plants
Passive absorption of water This type of water
absorption does not require the use of metabolic energy
& by metabolic activity like transpiration pull. This
creates tension or force in the movement of water
upwards into the xylem sap. More is the transpiration
rate, higher is the absorption of water.
Role of root hairs
The root contains some tubular, hair-like and
unicellular structures refers as “Root hair” is the water
permeable region. Root hairs are the outgrowths which
arise from the epidermal layer refers as “Piliferous
layer”.
The cell wall of root hair consists of a double layer
membrane. Pectin is present in the outer layer and
cellulose is present in the inner layer of the cell wall.
Under the cell wall, there is a cytoplasmic
membrane which is selectively permeable.

14. 7. Absorption of water in plants
Mechanism & path for absorption of water by the root
hairs of the plant is through the process of osmosis.
After entering into the root hair, the water will cross
the epidermis or piliferous layer of the root system. Then,
from the epidermis to the root cortex to
the endodermis consists of suberic to the pericycle to
the root xylem i.e. perixylem and metaxylem. Therefore,
water will store in the xylem root system.

15. Symplast and Apoplast
Symplast: symplastic pathway, water moves across the symplast,
which consists of the cytoplasm and plasmodesmata (minute
connections between the cytoplasm of adjacent cells) also refers to the
continuous arrangement of protoplasts of a plant, which are
interconnected by plasmodesmata and consists of protoplast
Apoplast : The apoplast pathway is where water takes a route going
from cell wall to cell wall, not entering the cytoplasm at any point.
Apoplast consists of nonprotoplasmic parts such as cell wall and
intracellular space and composed of non-living parts of a plant.

16. Symplast and Apoplast

17. 8. Ascent of Sap
Ascent of
Sap
• The upward movement of water from the root to aerial parts of
the plant body is called ascent of sap or often called
translocation of water.
Ascent of
Sap
• The water after being absorbed by the roots is distributed to all
parts of the plant (excess of which is lost through transpiration).
In order to reach the topmost parts of the plant, the water has
to move upward through the stem. This upward movement of
water is called as Ascent of Sap.
Ascent of
Sap
•There is fascinating to understand how water moves in plants to such
great heights such as 300 ft. or more. For example, trees like
Sequoia sempervirens are as tall as‟ 399.3ft. These plants transport
water through their stem to such great heights is „incredible

18. 8. Ascent of Sap
This experiment is to determine which of the stem components are used in the
ascent of sap. However the removal of cortex and phloem by girdling
experiment does not affect the movement of sap. Thus it can be concluded
that xylem is alone responsible for the ascent of sap.

19. Theories of Ascent of Sap
Root Pressure Theory:
Under certain conditions, plants exhibit
exudation of the xylem sap from the
stump of a freshly cut stem.
Most of such exudations result from the
development of a pressure in the dilute
sap of the xylem ducts resulting from
the operation of mechanism in the root
s, termed the root pressure.
It can also be shown experimentally
that water is forced up the stem by
root pressure.
•This led to the view that root pressure
is the mean by which water is raised in
tall trees.
•The maximum of observed root
pressure is 5 to 6 bars. However, many
trees have height much in excess of 10
m. Furthermore, many tall trees e.g.,
conifers have no demonstrable root
pressure.

20. Theories of Ascent of Sap
Cohesion-tension or transpiration pull
(i) Water forms a continuous column
extending between the root and the leaf
parenchyma cells through the xylem ducts.
This is also called hydrostatic system.
(ii) Evaporation from the surface of the
parenchyma cells of the leaf (or other issues)
increases the water potential (Ψ) and they
withdraw water from the xylem elements.
This puts the column of water under a strain
or tension.
(iii) because of an attraction between water
molecules and the molecules of the wall of
the tube (adhesion), the water column is
put under stress but does not result in
putting the water away from the enclosing
wall.
(iv) Water molecules have a strong cohesion
force due to hydrogen bonding between
water molecules.
Hence water is pulled up in chain and
evaporated from leaves in a channel
favoring lifting of water molecule by
absorption.

21. Theories of Ascent of Sap
Strong Views of Dixon’s Theory:
(i) The hypothesis is demonstrated by a
movement of water through the stem
when it is actually under tension.
Using leafy twigs of different kinds of
woody plants it has been demonstrated
that there is a rise of 118 cm of mercury,
43.5 cm above the atmospheric pressure.
It is believed that the water intended for
evaporation normally does not come from
vacuole.
On the other hand, it comes from the
xylem along the apparent free spaces (cells
walls) of the cells in between.
The rate of transpiration becomes more
than the rate of movement of water.
The increased water potential of mesophyll
cells may be helpful to them to withdraw
water from the wet walls.

22. Transpiration is the process by which moisture is carried through plants from roots
to small pores on the underside of leaves, where it changes to vapor and is released to
the atmosphere. Transpiration is essentially evaporation of water from plant leaves.
The following three major types of transpiration.
(1)Stomatal Transpiration
(2) Lenticular Transpiration and
(3) Cuticular Transpiration.
Transpiration mainly takes place through surface of leaves.
Transpiration is the process where plants absorb water through the roots and then
give off water vapor through pores in their leaves.
An example of transpiration is when a plant absorbs water in its roots.
9. Transpiration

23. During daytime, guard cells photosynthesis due to which osmotic pressure increases.
The guard cells absorb water from the neighboring cells. Guard cells become
turgid. As a result, the outer thin walls of guard cells are pushed out and the inner
thicker walls are pulled inwards resulting in stomata to open.
During night or in a condition of water scarcity, guard cells are in a flaccid state and
remain closed. Transpiration is the main driving force for the ascent of sap
Stomatal transpiration : Stomata are the tiny pores present in the epidermal surface of
leaves. The pores are guarded by two kidney-shaped cells known as guard cells.
The inner wall of guard cell towards the stomata is thicker as compared to the outer
walls. Also, the peculiar arrangement of the microfibrils of the guard cells also aids in
opening and closing of the stomatal aperture.
The microfibrils are oriented radially rather than longitudinal.
9. Transpiration

24. Theory 1. Starch Sugar Inter-conversion Theory:
Steward (1964) proposed another modified scheme of inter-conversion of starch and
sugar for stomatal movement. He believes that conversion of starch to Glucose -1
phosphate is not sufficient. It should be converted to glucose in order to increase
sufficient osmotic pressure. For this, ATP is also required which means that the
process should be through respiration in presence of oxygen. Guard cell carries
enzymes like Phosphorylase, Phosphoglucomutase, Phosphatase and Phosphorylase.
These enzymes help in opening and closing of the stomata.
9. Transpiration
Demerits of the starch-sugar inter-conversion theory:
In the presence of light when starch disappears from guard cells, malic acid appears
and not the sugars. As per it, O.P. of guard cells increases due to the formation of
glucose-1- phosphate in guard cells but it is found that the presence of phosphate
ions causes the development of same O.P as does the presence of glucose-phosphate.

25. 2. Cohesion Adhesion Tension Theory
It was originally proposed by Dixon
and Joly in 1894 and Askenasy (1895),
then it was greatly supported by Renner
(1911, 1915), Curtis and Clark (1951),
Bonner and Galston (1952) and Gramer
and Kozlowski (1960).
This theory however describes the
movement of water from roots to the
leaves of a plant.
Because of osmosis water from soil reach
the xylem of roots of a plant. Water
molecules are bonded to each other by
hydrogen bonding, hence water form a
string of molecules during its movement
toward xylem.
he water molecules stick together and
get pulled up by the force called
tension. This force is exerted because of
the evaporation at the surface of the
leaf.
9. Transpiration

26. Features of Cohesion Adhesion Theory
Cohesive and adhesive properties of
water molecules to form an unbroken
continuous water column in the xylem.
Transpiration pull or tension exerted
on this water column.
Xylem vessels are tubular structures
extending from roots to the top of the
plants. Cells are placed one above the
other, with their end walls perforated
forming a continuous tube.
These are supported by xylem
tracheids which are characterised by
having pores in their walls.
Conclusion:
It is clear from the above discussion
that water column in the xylem are
continuous
9. Transpiration

27. 10. Guttation is the exudation of drops of xylem sap on the tips or edges of
leaves of some vascular plants, such as grasses, and a number of fungi.
Guttation is a phenomenon which is caused by the root PRESSURE. It
generally happens in the morning when there is no/less transpiration and
the excess root pressure cause the water to ooze out from the special
openings called hydathodes.
Transpiration is the excessive loss of water from the aerial portion of plants as water
vapours. But, Guttation is the process of secretion of liquid water through the leaf
tips in some plants.
A hydathode is a type of pore, commonly found in angiosperms, that secretes water
through pores in the epidermis or leaf margin, typically at the tip of a marginal
tooth or serration

28. 11. ANTI-TRANSPIRANTS
 Definition of antitranspirant. : a substance (such as pine oil) that is usually
sprayed on plant surfaces (as of the leaves and stems) to reduce transpiration and
inhibit water loss.
 Antitranspirants are substances applied to the plants for the purpose of reducing
transpiration (water loss) without causing a significant effect on other plant
processes, such as photosynthesis & growth. They have been used with some success in
horticulture, especially in the ornamental industry
 Antitranspirants are compounds applied to the leaves of plants to reduce
transpiration. They are used from Christmas trees, on cut flowers, on newly
transplanted shrubs, and in other applications to preserve and protect plants from
drying out too quickly.
 Antitranspirants are of two types: metabolic inhibitors and film-
forming antitranspirants. Metabolic inhibitors reduce the stomatal opening and
increase the leaf resistance to water vapour diffusion without affecting carbon
dioxide uptake. Examples include phenylmercury acetate, abscisic acid (ABA), and
aspirin.
 Film-forming antitranspirants form a colorless film on the leaf surface that allows
diffusion of gases but not of water vapour. Examples include silicon oil , waxes

29. 12. MINERAL ABSORPTION
Plants receive mostly carbon and oxygen in a form of CO2 from air and
partly hydrogen. These nutrients enter a plant in a molecular form. Thanks
to leaves, stems, and eventually generative organs, most plants can also
receive other nutrients, such as N, P, K, Ca, Mg, microelements, etc., mostly
in a form of soluble salts of certain concentration. Such way of nutrition is
marked as foliar (folic) nutrition. Besides, plants receive all nutrients and
water by roots.
Nutrient uptake by roots is shared by all young root parts and especially
by a zone of root hairs which up to hundreds of times increases the surface
area of a root. The number of root hairs in 1 mm fluctuates according to
humidity, soil aeration and plant type.
By its presence in the soil environment, the root excretions influence the
solubility of some mineral substances (phosphorus), and with the content of
sugars and amino acids support the development of soil microflora
(mycorrhiza).

30. Active absorption
Active uptake of ions is one of the most important features of life processes.
It is accomplished through the coupling of diffusion fluxes to the exergonic
reactions that take place in the bulk of the membrane.
The transfer of ions occurs at the expense of the free energy liberated in
chemical reactions. As a rule, this is the energy of hydrolysis of ATP.
Carrier concept: By Vanden honert. According to
this theory some specific carrier molecules made
up of proteins are present in cell membrane of
root cell which absorbs both the ions and form
ion- carrier complex. This complex is break inside
the cell membrane with expenditure of energy.
Cytochrome Pump Theory : By Lundegardh
Burstorm (1933) According to this theory, only
anions are absorbed by active mechanism
through cytochrome pumping and absorption of
cation is passive process. According to
cytochrome pump theory respiration is called as
anion respiration.

31. Protein-Lecithin Theory:
By Bennet Clark According to this theory a phospholipid lecithin in root cell
membrane works as carrier for both type of ions
Goldacre: A contractile protein is associated with absorption of minerals.
P.R. Stout and Hoagland (1939) proved that mineral salts are translocated
through xylem along with transpiration pull
(exp. with help of radioisotopes).
Passive absorption
Absorption of ions without the use of
metabolic energy is known as passive
absorption. This type of absorption is carried
out by purely physical forces. Briggs and
Robertson (1957) demonstrated the passive
absorption of ions by root system.In most
cases, the movement of mineral ions into the
root occurs by diffusion.

32. 1. Ion Exchange: Firstly, if uptake of nutrient on ions exceeds cation uptake,
hydroxyl and bicarbonate ions are transported outwardly from inside the
cell. If cation absorption is rapid than the anions, some hydrogen ions are
exchanged by cells.
2. Secondly, excess of cations uptake is accompanied by the simultaneous
bicarbonate absorption and hydroxyl ions, while excess anions may be
taken up with hydrogen ions.
2. Carbonic Acid Exchange Theory:
CO2 from respiration is continuously
released at the root tip. It combines with
the water to form carbonic acid (H2CO3)
and the latter dissociates into H+ and
HCO3
– ions.
The H+ ions exchanges with cations are
absorbed on the clay micelle and enter
the soil solution and diffuse to the root
surface.

33. DONNAN EQUILIBRIUM
This theory takes into account the effect of fixed or indifussible ions.
A differentially permeable membrane separates cell from the external
solution. The cell has a concentration of anions to which the membrane is
impermeable.
When tissue cells are in a protein-containing fluid, the Donnan effect of the
cytoplasmic proteins is equal and opposite to the Donnan effect of the
extracellular proteins. The opposing Donnan effects cause chloride ions to
migrate inside the cell, increasing the intracellular chloride concentration
If a membrane which is freely permeable to
the cations and anions present in the external
medium is used, an equal number of cations
and aninos will diffuse across the membrane
into the cell till equilibrium is reached.
However, additional cations will be required
to balance the negative charge of the “fixed”
anions on the inside of the membrane.
Therefore, the cation concentration would be
greater in the internal than in the external
solution.

34. Uniporters, symporters, and antiporters are proteins that are used in ​transport​ of
substances across a cell membrane. Symporters and antiporters are involved in
active transport. Antiporters transport molecules in opposite directions,
while symporters transport molecules in the same direction.
An antiporter
(also called exchanger or counter-
transporter) is a cotransporter and
integral membrane protein involved
in secondary active transport of two
or more different molecules or ions
across a phospholipid membrane
such as the plasma membrane in
opposite directions
A Symport
Integral protein which moves two or more molecule types across the membrane in
the same direction. Antiport- Integral protein which moves two or more molecule
types across the membrane in the opposite direction.